Acrylic H 50 tested
The H50 (32V) has been in the house for almost 4 weeks, needs to be tested a bit before one can draw a conclusion.
have tried various speakers and subwoofers.
everything from 10" speakers and up to 15" sub.
but..... I landed on a setup, as the amplifier is sold as a "bookshelf"
Some old classics Mission M70.
Klipsch SW-110.
And the combo played out of the office (the office was too small), and into the kitchen/living room.
The amplifier connects easily and quickly to the network and other wireless devices.
and no ugly power on/off sound. as some of the YouTubers have reported.
I also liked that you could remove the terminal screws, so you could more easily install the speaker cables👍
The amplifier connects to Spotify without problems on Android.
and you can easily select the amplifier as playback, and it happens in seconds.
AirPlay 2 works equally well from both iPhone and iPad.
As a hifi head, I am happy that Tidal has support, since Tidal has higher sound quality.
You notice this if you compare playbacks of the same song on both Spotify and Tidal.
But I miss Youtube music support, since it also has higher sound quality than Spotify. Hopefully it will come later. Since this is in software and not hardware.
I also like that the H50 has the option to use the API for a smart home solution, but I have to try that later.
I don't need this yet,
since the amplifier has Alexa support.
It was very easy to link to Alexa, and works excellently with voice control.
Another bonus of the amplifier being Alexa supported is that it automatically came up in my smart home system Homey Pro. Since I have linked Alexa and Homey Pro.
The HDMI arc is one of the highlights of this amplifier, especially if you don't want to have more than one remote control when using it with a TV.
You just plug in the HDMI cable and the TV turns off the internal speakers and the sound comes straight to the H50. And the volume on the H50 is controlled by the TV/TV remote control.
I liked this better than the remote control that comes with the H50.
The remote control that comes with it is a bit of a letdown, because it is of the simplest kind.
But it works as intended.
But this is nothing to complain about, since remote controls are almost 2000s.
In 2025, App control is the thing, since the music player is operated wirelessly from a digital device.
The 4stream app is very easy to use, but feels a little unfamiliar.
and I have one complaint about the app, the EQ in the app.
it has a little too few notches and adjusts the sound.
so I'm considering spending $20 on ACPWorkbench Audio Effect Tool.
but it will have to wait a bit since I'm planning to change PC soon. and the license is tied to 1 specific PC.
price/content in relation to competitors.
Acrylic actually has a hidden secret there 👍
I have to pay import duty of course. but.... Acrylic was so nice to set the value at $12 !!!!!!!!
So the total price was about 23-25% lower than if I had imported from a competitor with roughly the same features.
I am so satisfied that I will buy the S50 pro, or som of the Diy cards from acrylic.
And diy against 2 old diy Cristiansand's
lyd fabrikk, Elektrokompaniet power amplifiers dravings from the early 2000s.
https://www.arylic.com/products/h50-airplay2-amplifier
info pictures borrowed from the manufacturer's website.
The other pictures were taken in my kitchen
have tried various speakers and subwoofers.
everything from 10" speakers and up to 15" sub.
but..... I landed on a setup, as the amplifier is sold as a "bookshelf"
Some old classics Mission M70.
Klipsch SW-110.
And the combo played out of the office (the office was too small), and into the kitchen/living room.
The amplifier connects easily and quickly to the network and other wireless devices.
and no ugly power on/off sound. as some of the YouTubers have reported.
I also liked that you could remove the terminal screws, so you could more easily install the speaker cables👍
The amplifier connects to Spotify without problems on Android.
and you can easily select the amplifier as playback, and it happens in seconds.
AirPlay 2 works equally well from both iPhone and iPad.
As a hifi head, I am happy that Tidal has support, since Tidal has higher sound quality.
You notice this if you compare playbacks of the same song on both Spotify and Tidal.
But I miss Youtube music support, since it also has higher sound quality than Spotify. Hopefully it will come later. Since this is in software and not hardware.
I also like that the H50 has the option to use the API for a smart home solution, but I have to try that later.
I don't need this yet,
since the amplifier has Alexa support.
It was very easy to link to Alexa, and works excellently with voice control.
Another bonus of the amplifier being Alexa supported is that it automatically came up in my smart home system Homey Pro. Since I have linked Alexa and Homey Pro.
The HDMI arc is one of the highlights of this amplifier, especially if you don't want to have more than one remote control when using it with a TV.
You just plug in the HDMI cable and the TV turns off the internal speakers and the sound comes straight to the H50. And the volume on the H50 is controlled by the TV/TV remote control.
I liked this better than the remote control that comes with the H50.
The remote control that comes with it is a bit of a letdown, because it is of the simplest kind.
But it works as intended.
But this is nothing to complain about, since remote controls are almost 2000s.
In 2025, App control is the thing, since the music player is operated wirelessly from a digital device.
The 4stream app is very easy to use, but feels a little unfamiliar.
and I have one complaint about the app, the EQ in the app.
it has a little too few notches and adjusts the sound.
so I'm considering spending $20 on ACPWorkbench Audio Effect Tool.
but it will have to wait a bit since I'm planning to change PC soon. and the license is tied to 1 specific PC.
price/content in relation to competitors.
Acrylic actually has a hidden secret there 👍
I have to pay import duty of course. but.... Acrylic was so nice to set the value at $12 !!!!!!!!
So the total price was about 23-25% lower than if I had imported from a competitor with roughly the same features.
I am so satisfied that I will buy the S50 pro, or som of the Diy cards from acrylic.
And diy against 2 old diy Cristiansand's
lyd fabrikk, Elektrokompaniet power amplifiers dravings from the early 2000s.
https://www.arylic.com/products/h50-airplay2-amplifier
info pictures borrowed from the manufacturer's website.
The other pictures were taken in my kitchen
Attachments
Why do I have to use the "incognito" or "in private" window?
- By jackinnj
- The Lounge
- 4 Replies
Attachments
F2a tube as pentode SE
- By Hugo145
- Tubes / Valves
- 71 Replies
Hello,
I am considering to use Siemens F2a tube in pentode mode as SE output. However all schematics and load lines that I could find online use F2a triode strapped (which is perfectly fine, but this build I want to experiment with pentode). I could not find Shindo Cortese schematic either.
According to the datasheet suggested pentode operation in Class A is Ua=Ug2=250V with 60 Ohm cathode resistor yielding ~6.5V bias and 2.2 kOhm load.
Load line therefore looks like this
I am a bit puzzled with the signal voltage swing of just 13Vpp, what am I supposed to use in a driver stage?
Continuing the "Euro pentode" theme, classic C3m and C3g tubes have amplification factor of 19 and 41 respectively. However my source DAC can deliver up to 6Vpp itself, gain is too high.
Do I use a step-down interstage? Do I use C3m/C3g as cathode follower instead and use a step-up interstage?
Any ideas of a viable C3m/C3g - F2a pentode SE amplifier are welcome.
Thanks.
I am considering to use Siemens F2a tube in pentode mode as SE output. However all schematics and load lines that I could find online use F2a triode strapped (which is perfectly fine, but this build I want to experiment with pentode). I could not find Shindo Cortese schematic either.
According to the datasheet suggested pentode operation in Class A is Ua=Ug2=250V with 60 Ohm cathode resistor yielding ~6.5V bias and 2.2 kOhm load.
Load line therefore looks like this
I am a bit puzzled with the signal voltage swing of just 13Vpp, what am I supposed to use in a driver stage?
Continuing the "Euro pentode" theme, classic C3m and C3g tubes have amplification factor of 19 and 41 respectively. However my source DAC can deliver up to 6Vpp itself, gain is too high.
Do I use a step-down interstage? Do I use C3m/C3g as cathode follower instead and use a step-up interstage?
Any ideas of a viable C3m/C3g - F2a pentode SE amplifier are welcome.
Thanks.
Apica - a 8" Bookshelf with planar Tweeter
I would like to introduce my latest design, the Apica.
It has an 8” woofer with honeycomb cone and a planar tweeter with waveguide.
It has a 20 liter closed cabinet with high pass and delivers bass down to about 37Hz (f3).
Here are the measurements of the driver in the housing without crossover:
And the measurements with crossover:
Please note that this measurement is only valid from 200Hz upwards and does not show the real behavior in the bass.
Detailed information is available on our website, unfortunately only in German:
https://www.der-akustische-untergrund.de/speakers/advanced-level-projects/apica/
The project was created in cooperation with hs-sound.de, but I will not be involved in the sale.
https://www.hs-sound.de/Apica
It has an 8” woofer with honeycomb cone and a planar tweeter with waveguide.
It has a 20 liter closed cabinet with high pass and delivers bass down to about 37Hz (f3).
Here are the measurements of the driver in the housing without crossover:
And the measurements with crossover:
Please note that this measurement is only valid from 200Hz upwards and does not show the real behavior in the bass.
Detailed information is available on our website, unfortunately only in German:
https://www.der-akustische-untergrund.de/speakers/advanced-level-projects/apica/
The project was created in cooperation with hs-sound.de, but I will not be involved in the sale.
https://www.hs-sound.de/Apica
I am struggling to model a driver in Hornresp. Help?
- Multi-Way
- 6 Replies
I'm currently attempting to model a simple front-loaded horn for a cone driver. (I'm aware this is not ideal, but this one has a fairly high EBP and thus should be pretty suitable.) I'd like to cross it over as low as possible.
The result is not good. Really not good. "How the heck did I lose all of my high frequency response on axis?" bad.
What did I screw up?
The result is not good. Really not good. "How the heck did I lose all of my high frequency response on axis?" bad.
What did I screw up?
Power Supply PCB for DC-DC modules as XL4015, XL6009 and others
- By stef1777
- Power Supplies
- 37 Replies
Attachments
Another open baffle build
- By Tube Radio
- Multi-Way
- 4 Replies
I've got the following speaker that I use with a communications receiver. The receiver receives from 6-9kHz and has the typical AM audio response.
I'd like to go open baffle as I like how an open baffle speaker looks. Should I keep the woofer like it is or rotate it on its side to make the baffle smaller in height?
I've got a 2' X 2' piece of 3/4" thick wood left over from the other open baffle project that I will use to make the baffle and bottom piece. I also have a couple right angle brackets left over from the same project.
I'd like to go open baffle as I like how an open baffle speaker looks. Should I keep the woofer like it is or rotate it on its side to make the baffle smaller in height?
I've got a 2' X 2' piece of 3/4" thick wood left over from the other open baffle project that I will use to make the baffle and bottom piece. I also have a couple right angle brackets left over from the same project.
Is it best to use a non-axisymmetric waveguide?
A waveguide with different angles on H&V might appear to help with ceiling reflections and even reduce baffle spacing.. but does it achieve these goals or make them harder to reach?
If you want to make one dimension more narrow and still have it work down to the same frequency, it needs to be both taller and deeper.
Often this is not what you see. When the vertical is cut down, or is designed to meet the horizontal at the mouth, it cannot maintain control of the lower frequencies as the horizontal can. The crossover frequency may need to be raised to avoid this diffracted energy which is not within the directivity target.
At that high crossover frequency, wavelengths are shorter and the effective driver spacing in wavelengths falls apart, making baffle spacing worse than for a wider vertical angle.
If you want to make one dimension more narrow and still have it work down to the same frequency, it needs to be both taller and deeper.
Often this is not what you see. When the vertical is cut down, or is designed to meet the horizontal at the mouth, it cannot maintain control of the lower frequencies as the horizontal can. The crossover frequency may need to be raised to avoid this diffracted energy which is not within the directivity target.
At that high crossover frequency, wavelengths are shorter and the effective driver spacing in wavelengths falls apart, making baffle spacing worse than for a wider vertical angle.
Experimental Herzog-Style Tube-Type Preamp
- Instruments and Amps
- 6 Replies
Here's a circuit I came up with to honor the original Garnet Herzog distortion unit. Comments are welcome. Also, tube-amp experts are invited to offer criticisms and/or point out mistakes I may have made in the design. I have not built it, so it must be considered experimental circuitry. Yet, I believe it will work. Thanks.
Tube-Type Overdrive Preamp
By H.K. Richter
Here is my design for a preamp intended for producing distortion inspired by the original Garnet Herzog amp, though this is wholly my own design. The Herzog was built for the guitarist Randy Bachman, famous in the ‘60s while playing with the band The Guess Who, using the Herzog on hit song “American Woman”. And in the ‘70s he had the hit “Takin’ Care of Business” with his own band, Bachman Turner Overdrive, again using the Herzog, which had been made for him by Canadian engineer Gar Gillies, founder of the Garnet amp company. In the ‘60s, distorted guitar sounds were achieved by using amps turned up to maximum volume, since there were few stomp-box types of effects at the time. Bachman’s distorted sound therefore stood out, and thus, after the “American Woman” hit, the Herzog was suddenly in demand by other guitarists, and Garnet amps, already popular, also saw sales increase greatly for all of their products.
The design used by Gar Gillies for the Herzog was likely from his low-power practice-amp called the Banshee, with which he simply replaced the speaker with an output jack sending out a high-impedance line-level signal instead of a speaker signal. Hence, the Herzog was one of the first of all purpose-built distortion effect boxes that sounded good. Yet, the Banshee had earlier been based on the Fender Champ. So, the first version of the Herzog, made at Randy Bachman’s request (and with his help), was just a complete low-power single-end amp having a line out instead of a speaker. Later versions, however, included both a line out jack and a speaker jack. In any case, after studying singe-ended amps, and having previously become acquainted with the Herzog schematic, I decided to come up with something similar, though my design is not based on an existing amp, but uses circuits obtained from the original 1965 RCA Receiving Tube manual, along with the design tables and tube characteristics graphs in that manual. I also studied design tables and schematics online and investigated many forums about tube-amps.
Example Source: https://www.thetubestore.com/guitar-amp-schematics
My design is therefore unique to me, though similarities between my circuit and many other single-ended amp circuits are evident, because there are scant few topologies available that actually work properly, and which were long ago published by vacuum tube manufacturers, such as RCA, in their tube manuals. It’s from those manuals that Leo Fender and all other early guitar-amp makers obtained their first circuits, so then I decided to do the same thing, instead of copying their designs like so many other guitar-amp makers had done early on (e.g., Garnet, Marshall, etc.).
Here is the power supply for my Overdrive Preamp. I call this overall design a preamp because that’s actually what it is, despite having what is normally used as an output stage. Just as with the Herzog, the output tube is used to make the final circuit a gain stage, so that it serves as a preamp tube, though it was designed as an output tube. The reason is to obtain the sound of its distortion when overdriven.
Notice the Input Tone control in the input triode’s circuit. I obtained that idea from an old book from the ‘50s called “High Fidelity Techniques”, by MIT professor John H. Newitt. Copyrighted in 1955, the book must have become popular with audiophiles back then, since it had been reprinted seven times as of four years later (I have a 7th printing). How many more reprints it had after that I don’t know. The point is that it contains a wealth of information and many tube circuits the author actually built and tested, including the said tone-control. This one, however, mostly affects the mids, leaving extreme highs and lows alone.
The Gain control is of my own device and is used to adjust the current through the input triode. When all the way up, the gain for the input triode is 13, despite the rated maximum for such circuit at 17 and an absolute maximum gain for the triode at only 19. Yet, the next triode provides a fixed gain of 16. However, any of the pin-compatible tubes listed in the diagram will provide more gain from both stages. Here’s a chart.
Tube 1st Triode 2nd Triode Maximum
Type Gain In Circuit Gain In Circuit Gain Rating
12AU7A 13 16 19
12AY7 23 35 44
12AT7 24 37 60
12AX7A 32 62 100
For the least gain, and therefore the least amount of distortion, keep the 12AU7A, but for more gain and distortion, experiment by substituting something other than the said 12AU7A, for which this design was originally tailored. But just because you’ll get more gain, that does not mean you’ll get better tone. Tonality is subjective. Some guitarists like more fuzz than others, so a builder of this design must decide which tube sounds best to them. Have one of each on hand during final testing so you can contrast and compare. Know beforehand, however, that more gain, giving increased distortion, logically corresponds to more output volume. That’s why there’s such a large-valued pot as the Master Volume control. 1M should be enough to work for a volume pot in this case, but if you find the output too strong with a higher-gain tube, increase the value of the resistor at the 8-ohm tap of the output transformer.
Next in the signal path is the Dist 1 control, which sets the amount of signal going to the second triode, and thus how greatly that triode is overdriven. Then comes the Dist Tone control, which is a low-pass filter with a high cutoff and only affects the highs but if it’s turned down the volume goes down too. So, it must be adjusted to taste by trial-and-error, then left at a preferred position. Following that control is the Dist 2 control which affects the signal level going to the output tube. The reason it’s labeled as a distortion control instead of as a volume control is that it is meant to adjust how much the output tube is overdriven. The primary goal is to get the output tube clipping between 10% and 20%, for the best distortion tone. Preamp tubes will clip, of course, but their distortion involves odd-order harmonics along with even-order harmonics, which is not as sweet as even-order harmonics alone. Also, some preamp tubes, like the 12AX7A, can have an unwanted raspiness in their distortion, and some just sound better than others. But output tubes of any type were originally designed to emphasize even-order harmonics in their distortion. That’s what makes tube-amps sound good when cranked up loud. It’s the even-order harmonics from the output tubes (plus fuzz from the output-transformer).
Much of the output’s sound also comes from the output transformer. The transformer chosen for the output of this project is made to sound as much like one from the ‘50s as possible, using modern materials. And its when the output transformer is saturated that it too introduces even-order harmonics into the fuzz it produces.
The dummy load is there to simulate a speaker, because the output stage needs what it would see as a normal load. But it can be replaced by a real speaker, if desired, or yet another output jack can be installed and labeled properly, such as “Spk”, along with a switch that allows the user to choose to use an external speaker instead, although this amp would only put out about 5 W RMS. In any case, the chosen output tube is not there to drive a speaker, but to get its sound in a line-level output signal.
There is also a choice to be made about which output tube is preferred. The list of pin-compatible substitutes is given in the diagram, together with their maximum possible plate dissipation (wattage) ratings. But there too, the sound of the different types must be compared during final testing, to know which type sounds best to the builder.
EOF
Tube-Type Overdrive Preamp
By H.K. Richter
Here is my design for a preamp intended for producing distortion inspired by the original Garnet Herzog amp, though this is wholly my own design. The Herzog was built for the guitarist Randy Bachman, famous in the ‘60s while playing with the band The Guess Who, using the Herzog on hit song “American Woman”. And in the ‘70s he had the hit “Takin’ Care of Business” with his own band, Bachman Turner Overdrive, again using the Herzog, which had been made for him by Canadian engineer Gar Gillies, founder of the Garnet amp company. In the ‘60s, distorted guitar sounds were achieved by using amps turned up to maximum volume, since there were few stomp-box types of effects at the time. Bachman’s distorted sound therefore stood out, and thus, after the “American Woman” hit, the Herzog was suddenly in demand by other guitarists, and Garnet amps, already popular, also saw sales increase greatly for all of their products.
The design used by Gar Gillies for the Herzog was likely from his low-power practice-amp called the Banshee, with which he simply replaced the speaker with an output jack sending out a high-impedance line-level signal instead of a speaker signal. Hence, the Herzog was one of the first of all purpose-built distortion effect boxes that sounded good. Yet, the Banshee had earlier been based on the Fender Champ. So, the first version of the Herzog, made at Randy Bachman’s request (and with his help), was just a complete low-power single-end amp having a line out instead of a speaker. Later versions, however, included both a line out jack and a speaker jack. In any case, after studying singe-ended amps, and having previously become acquainted with the Herzog schematic, I decided to come up with something similar, though my design is not based on an existing amp, but uses circuits obtained from the original 1965 RCA Receiving Tube manual, along with the design tables and tube characteristics graphs in that manual. I also studied design tables and schematics online and investigated many forums about tube-amps.
Example Source: https://www.thetubestore.com/guitar-amp-schematics
My design is therefore unique to me, though similarities between my circuit and many other single-ended amp circuits are evident, because there are scant few topologies available that actually work properly, and which were long ago published by vacuum tube manufacturers, such as RCA, in their tube manuals. It’s from those manuals that Leo Fender and all other early guitar-amp makers obtained their first circuits, so then I decided to do the same thing, instead of copying their designs like so many other guitar-amp makers had done early on (e.g., Garnet, Marshall, etc.).
Here is the power supply for my Overdrive Preamp. I call this overall design a preamp because that’s actually what it is, despite having what is normally used as an output stage. Just as with the Herzog, the output tube is used to make the final circuit a gain stage, so that it serves as a preamp tube, though it was designed as an output tube. The reason is to obtain the sound of its distortion when overdriven.
Notice the Input Tone control in the input triode’s circuit. I obtained that idea from an old book from the ‘50s called “High Fidelity Techniques”, by MIT professor John H. Newitt. Copyrighted in 1955, the book must have become popular with audiophiles back then, since it had been reprinted seven times as of four years later (I have a 7th printing). How many more reprints it had after that I don’t know. The point is that it contains a wealth of information and many tube circuits the author actually built and tested, including the said tone-control. This one, however, mostly affects the mids, leaving extreme highs and lows alone.
The Gain control is of my own device and is used to adjust the current through the input triode. When all the way up, the gain for the input triode is 13, despite the rated maximum for such circuit at 17 and an absolute maximum gain for the triode at only 19. Yet, the next triode provides a fixed gain of 16. However, any of the pin-compatible tubes listed in the diagram will provide more gain from both stages. Here’s a chart.
Tube 1st Triode 2nd Triode Maximum
Type Gain In Circuit Gain In Circuit Gain Rating
12AU7A 13 16 19
12AY7 23 35 44
12AT7 24 37 60
12AX7A 32 62 100
For the least gain, and therefore the least amount of distortion, keep the 12AU7A, but for more gain and distortion, experiment by substituting something other than the said 12AU7A, for which this design was originally tailored. But just because you’ll get more gain, that does not mean you’ll get better tone. Tonality is subjective. Some guitarists like more fuzz than others, so a builder of this design must decide which tube sounds best to them. Have one of each on hand during final testing so you can contrast and compare. Know beforehand, however, that more gain, giving increased distortion, logically corresponds to more output volume. That’s why there’s such a large-valued pot as the Master Volume control. 1M should be enough to work for a volume pot in this case, but if you find the output too strong with a higher-gain tube, increase the value of the resistor at the 8-ohm tap of the output transformer.
Next in the signal path is the Dist 1 control, which sets the amount of signal going to the second triode, and thus how greatly that triode is overdriven. Then comes the Dist Tone control, which is a low-pass filter with a high cutoff and only affects the highs but if it’s turned down the volume goes down too. So, it must be adjusted to taste by trial-and-error, then left at a preferred position. Following that control is the Dist 2 control which affects the signal level going to the output tube. The reason it’s labeled as a distortion control instead of as a volume control is that it is meant to adjust how much the output tube is overdriven. The primary goal is to get the output tube clipping between 10% and 20%, for the best distortion tone. Preamp tubes will clip, of course, but their distortion involves odd-order harmonics along with even-order harmonics, which is not as sweet as even-order harmonics alone. Also, some preamp tubes, like the 12AX7A, can have an unwanted raspiness in their distortion, and some just sound better than others. But output tubes of any type were originally designed to emphasize even-order harmonics in their distortion. That’s what makes tube-amps sound good when cranked up loud. It’s the even-order harmonics from the output tubes (plus fuzz from the output-transformer).
Much of the output’s sound also comes from the output transformer. The transformer chosen for the output of this project is made to sound as much like one from the ‘50s as possible, using modern materials. And its when the output transformer is saturated that it too introduces even-order harmonics into the fuzz it produces.
The dummy load is there to simulate a speaker, because the output stage needs what it would see as a normal load. But it can be replaced by a real speaker, if desired, or yet another output jack can be installed and labeled properly, such as “Spk”, along with a switch that allows the user to choose to use an external speaker instead, although this amp would only put out about 5 W RMS. In any case, the chosen output tube is not there to drive a speaker, but to get its sound in a line-level output signal.
There is also a choice to be made about which output tube is preferred. The list of pin-compatible substitutes is given in the diagram, together with their maximum possible plate dissipation (wattage) ratings. But there too, the sound of the different types must be compared during final testing, to know which type sounds best to the builder.
EOF
GB for Simple Cap-Mx Regulated Low-Noise PSU
- By xrk971
- Group Buys
- 155 Replies
Have you ever found yourself making a basic circuit that is so simple, that you say to yourself, "it's so simple I will just make it from scratch on veroboard..." It works so well and is so useful, it becomes an integral part of many of your future projects. Before you know it, you have hand-assembled on veroboard the same circuit a dozen times. Well that's what I have been doing whenever I needed a source of ultra quiet (battery-like) single-rail DC power in the range of 5v to about 32v and current under 1amp. I use this countless times for low noise headphone projects, DACs, etc. Well, I sort of got tired of making them from scratch and worked with JPS64 to put it on a simple 50mm x 75mm board the following: a CLC filter, an Easy-Peasy Juma cap multiplier, and a 78xx regulator, and throw in some smoothing caps, snubbers, output bypass caps, and LED power indicator, and input/output terminal blocks. I typically use a 12v 1000mA Class 2 transformer wall-wart ubiquitous with routers and switches that we accumulate over the years. That then powers a clean DC-DC step up converter to about 4v+ regulator dropout (circa 2v) above our needed voltage. So for example, if you need a clean 18v supply, add 5v or 23v as the DC-DC stepup output. Put that into this unit, and let its cap CLC filter, cap multiplier, and voltage regulator give you a clean source of 18v with ripple as low as 4uVrms (if you use a TO-220 formatted TPS7A4xxx LDO regulator). If you can live with 50uV noise,a simple 7818 regulator will work fine. I have used this on countless headphone amps and the noise floor measures flat like a battery. Absolutely no mains hum gets through.
Thanks to JPS64 for a great layout with all the customary via stitching and double planes of copper for low impedance current paths.
So here is the circuit:
This is what it looks like built up in prototype stage v1:
And here is the board will look like for the v2 (will be 1.6mm thick, 1oz copper, green mask, and ENIG finish):
Here is the top view of the parts placement. BOM for the board is relatively cheap if you are going with just a 78xx. You need an N-channel TO-220 MOSFET such as an IRF610 or the Fairchild equivalent. IRF510 etc works well too. A few caps and resistors, some connectors, and a basic inductor to keep the DC-DC noise even more isolated.
If interested in this little PSU board as a GB, please add your name, number of boards, and country to ship to below.
Like this:
DIYJohnDoe - 2 boards - USA
Pricing will be about $10 ea and tracked shipping in a padded bubble envelope mailer is the usual $5 in US, $10 for CAN, and $15 everywhere else. Maximum 8 boards per order for the above shipping prices.
Thanks,
X
Some supporting info, you can see in the photo below, a hand-made variant of this PSU (without a voltage regulator) powering my Aksa Lender preamp, the DC-DC step up is visible as well. Here I was running 48vdc output so a 78xx regulator could not have been used as they max out at 35vdc input:
Here is the FFT from the Aksa Lender showing the typical clean battery like noise floor:
Another example is the PSU that is built into the DCA Single ended Class A HPA (also without a VR):
Here is the typical FFT from the DCA:
Finally, another example is the similar PSU built into the Aksa-Lender preamp GB:
And typical FFT of the Aksa Lender putting out 20vpp into 7kohms:
So you can see how well this supply works in general and how I keep coming back to it. Just use a $4 to $7 DC-DC step up to get whatever voltage you need.
These types of DC-DC work well, for example:
DC DC 250w Boost Converter Step-up 10a Constant Current Power Supply LED Driver | eBay
400W 15A DC Step-up Constant Current Power Supply LED Driver Boost Converter | eBay
400W 15A DC Step-up Constant Current Power Supply LED Driver Boost Converter | eBay
DC-DC Step-up Boost Converter Constant Current Power Supply 10A 250W LED Driver 6472005271954 | eBay
Edit Feb 25, 2019: Member Twocents was a beta tester for v1 and he installed an eBay 5v TPS7A4xx LDO board on it - nice work!
And use a 12v 1000mA Class 2 Wall wart like this, for example:
Class 2 Power Supply Unit FL41A20U120V120A1000 Adapter 12V 1000mA Charger | eBay
Edit Mar. 14, 2019:
You can use the Wurth 774701 Choke:
https://www.digikey.com/product-detail/en/7447017/732-1418-ND/1638823/?itemSeq=289294179
https://katalog.we-online.de/pbs/datasheet/7447017.pdf
Version 2 of the board:
Thanks to JPS64 for a great layout with all the customary via stitching and double planes of copper for low impedance current paths.
So here is the circuit:
This is what it looks like built up in prototype stage v1:
And here is the board will look like for the v2 (will be 1.6mm thick, 1oz copper, green mask, and ENIG finish):
Here is the top view of the parts placement. BOM for the board is relatively cheap if you are going with just a 78xx. You need an N-channel TO-220 MOSFET such as an IRF610 or the Fairchild equivalent. IRF510 etc works well too. A few caps and resistors, some connectors, and a basic inductor to keep the DC-DC noise even more isolated.
If interested in this little PSU board as a GB, please add your name, number of boards, and country to ship to below.
Like this:
DIYJohnDoe - 2 boards - USA
Pricing will be about $10 ea and tracked shipping in a padded bubble envelope mailer is the usual $5 in US, $10 for CAN, and $15 everywhere else. Maximum 8 boards per order for the above shipping prices.
Thanks,
X
Some supporting info, you can see in the photo below, a hand-made variant of this PSU (without a voltage regulator) powering my Aksa Lender preamp, the DC-DC step up is visible as well. Here I was running 48vdc output so a 78xx regulator could not have been used as they max out at 35vdc input:
Here is the FFT from the Aksa Lender showing the typical clean battery like noise floor:
Another example is the PSU that is built into the DCA Single ended Class A HPA (also without a VR):
Here is the typical FFT from the DCA:
Finally, another example is the similar PSU built into the Aksa-Lender preamp GB:
And typical FFT of the Aksa Lender putting out 20vpp into 7kohms:
So you can see how well this supply works in general and how I keep coming back to it. Just use a $4 to $7 DC-DC step up to get whatever voltage you need.
These types of DC-DC work well, for example:
DC DC 250w Boost Converter Step-up 10a Constant Current Power Supply LED Driver | eBay
400W 15A DC Step-up Constant Current Power Supply LED Driver Boost Converter | eBay
400W 15A DC Step-up Constant Current Power Supply LED Driver Boost Converter | eBay
DC-DC Step-up Boost Converter Constant Current Power Supply 10A 250W LED Driver 6472005271954 | eBay
Edit Feb 25, 2019: Member Twocents was a beta tester for v1 and he installed an eBay 5v TPS7A4xx LDO board on it - nice work!
And use a 12v 1000mA Class 2 Wall wart like this, for example:
Class 2 Power Supply Unit FL41A20U120V120A1000 Adapter 12V 1000mA Charger | eBay
Edit Mar. 14, 2019:
You can use the Wurth 774701 Choke:
https://www.digikey.com/product-detail/en/7447017/732-1418-ND/1638823/?itemSeq=289294179
https://katalog.we-online.de/pbs/datasheet/7447017.pdf
Version 2 of the board:
Attachments
Two way naive “crossover” question
Disclaimer. As I value the low cost aspects of DIY and like to keep things simple my previous speaker builds have been utilizing a full range larger driver (and just letting it play) with a first order capacitor in front of the tweeter…..or utilizing an amplifier with a high pass filter with a separate subwoofer amp with low pass with or without DSP.
This is the first time I’m spending more than $19 on a tweeter, and I’d really like to hear it cleanly in its range (testing shows that it plays well with hardly any distortion all the way down to 500Hz). It’s an 8 inch planar/mid.
The 8 inch woofer frequency response looks nice up to 1k. My instinct was to in parallel low pass the 8 inch woofer at 800Hz and in parallel high pass the planar mid/tweeter at 800Hz….but then I thought this might make a hole at 800Hz and my second thought would be to low pass the 8 inch woofer the same; but high pass the planar mid/tweeter at 500hz.
I’ll subsequently post the specs and FR graphs below.
Any advice or commentary is greatly appreciated. Thank you.
This is the first time I’m spending more than $19 on a tweeter, and I’d really like to hear it cleanly in its range (testing shows that it plays well with hardly any distortion all the way down to 500Hz). It’s an 8 inch planar/mid.
The 8 inch woofer frequency response looks nice up to 1k. My instinct was to in parallel low pass the 8 inch woofer at 800Hz and in parallel high pass the planar mid/tweeter at 800Hz….but then I thought this might make a hole at 800Hz and my second thought would be to low pass the 8 inch woofer the same; but high pass the planar mid/tweeter at 500hz.
I’ll subsequently post the specs and FR graphs below.
Any advice or commentary is greatly appreciated. Thank you.
DSP Xover project (part 2)
- By chaparK
- Digital Line Level
- 3852 Replies
Good day all,
Some time ago I had started a thread about making a project with existing boards I had from a previous project. Well, after investigating several directions the project could follow, based on feedback from this forum and from other mates, I realized I needed to design a new board specifically tailored for the task.
This time the project is really on track and I'm happy to start this new thread with a picture of the recently born little baby. More info will follow shortly.
Cheers
chaparK
Some time ago I had started a thread about making a project with existing boards I had from a previous project. Well, after investigating several directions the project could follow, based on feedback from this forum and from other mates, I realized I needed to design a new board specifically tailored for the task.
This time the project is really on track and I'm happy to start this new thread with a picture of the recently born little baby. More info will follow shortly.
Cheers
chaparK
RCA transfomers, specs, thoughts, etc.
- By kilohertz
- Tubes / Valves
- 0 Replies
I'm in the preliminary, conceptual design phase of a DHT preamp and eventually a power amp, transformers are always (for me) the hardest part to find at a reasonable cost. I have an old RCA broadcast studio mixer/console, the 76B, yes the Sun Studios Elvis console, but it's in sad shape, restorable but only with lot's of work, but it is loaded with transformers. The one that caught my attention is the XT-2747 which is the output xfmr in the first mic mixer amp which uses a 1620. It's 2570R primary and 120R secondary, and I thought this might make a good output xfmr for a line stage preamp. I'm not decided on what tubes I will be using but have a number of DHTs in stock as well as many other triodes.
I've googled it but there's not much/any info out there.
I'm wondering if anyone out there has experience with this xfmr or any of the others in this console, or even better, specs 😀? The input xfmr looks like it might make a nice MC step up.
Below is the input section.
Cheers
I've googled it but there's not much/any info out there.
I'm wondering if anyone out there has experience with this xfmr or any of the others in this console, or even better, specs 😀? The input xfmr looks like it might make a nice MC step up.
Below is the input section.
Cheers
Cheap 3 way crossover question. Anyone have any ideas what this switch does?
- By westsounds
- Multi-Way
- 30 Replies
I just about to order a cheap crossover frequency filter. It’s for a project at home and I don’t want anything fancy and this one will suffice as long as it filters for a 3 way. I found this one on Amazon, seems to get good reviews. It doesn't explain the switch properly though. These things are often Chinese and instructions often get lost in translation.
Anyone have any ideas what exactly is the midrange adjust switch for ? It says 0hz 300hz, but that doesn’t make sense, you don’t run a midrange at 0 hz. Anyone know what it actually does?
Thanks for any responses.
https://www.amazon.com/DriSentri-Sp...0CHVTBTSD/ref=cm_cr_arp_d_product_top?ie=UTF8
What happened to all the low cost subwoofer DSP controllers?
- By CPTX
- Subwoofers
- 1 Replies
They suspiciously went off the market at approximately the same time. Did the manufacturers not like the target curve? Something else?
Bisesik DAC transformers for AKM V out
Up for sale a pair of these great sounding transformers. I used them with a SD Card player, which sported an AKM4495 chip.
I followed Ivans recommendations and added a R/C snubber at the output. These are much more expensive nowadays, price here is 100 Euro.
Preferably shipping to Europe regarding the expensive shipping to overseas.
I followed Ivans recommendations and added a R/C snubber at the output. These are much more expensive nowadays, price here is 100 Euro.
Preferably shipping to Europe regarding the expensive shipping to overseas.
Made a circuit on Express PCB Plus and wish to have PCB WAY make some boards. How to proceed?
- Electronic Design
- 2 Replies
You know how you to want to DIY something and it keeps getting put on the back burner? Well, this has been the case for me for over 30 years. Having some free time on my hands (thank you open heart surgery) I finally sat down at the computer with my hand drawn schematic and after many failed attempts arrived at a design and layout which might actually work. I will enclose a picture I took of the computer screen.
I did click the save as button so I probably do have the design on the computer. Now, what do I do. What files do I look for to send to PCB WAY?
I have absolutely no idea what the heck I'm doing just the thought that I would like to try to DIY one project in my life.
I apologize in advance if I've put this in the wrong section. Can anyone help me?
I did click the save as button so I probably do have the design on the computer. Now, what do I do. What files do I look for to send to PCB WAY?
I have absolutely no idea what the heck I'm doing just the thought that I would like to try to DIY one project in my life.
I apologize in advance if I've put this in the wrong section. Can anyone help me?
Group Buy: Peerless by Tympahny DFM-2535R00-08
- By sheeple
- Group Buys
- 112 Replies
[closed] The group buy is closed [/closed]
This thread provides a purchasing option for the 1-inch compression driver DFM-2535R00-08.
The driver is not available anymore in single units and hence unobtainable for consumers. With this group buy in cooperation with a Tymphany distributor from Germany DiYers can once again purchase a pair of the much discussed and HiFi-optimized compression driver that has some special properties.
The price for one driver DFM-2535R00-08 will be around 40 Euro excluding VAT. As an example, for buyers from Germany with 19 percent VAT, the end price is about 48 Euro total. Plus shipping from Germany to your destination. In general, it is possible to ship world wide, depending on your willingness to pay the costs. EU shipping is standard.
Please enter your contact details and the amount of drivers you want to buy in this google forms link: https://forms.gle/zszS5UC68y8xskvJ6
The condition for the distributor to stock the lot is an order of a minimum of 50 pairs / 100 pieces.
+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
We have reached: ████████████████████ 166%
+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
We have reached: ████████████████████ 166%
+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
When the necessary amount of buyers is reached, we will proceed with transaction. This can be done via bank account or PayPal.
- - - - - - - - - - - -
Some facts on the compression driver DFM-2535R00-08:
The compression driver is optimized for high quality sound reproduction, combining a polyimide surround with a coated titanium diaphragm. Thus it equally provides the benefits of a TI diaphragm, that is detailed high frequency reproduction, while also enabling the smoothness of a polymer surround. Additionally, it enables a low crossover frequency of 1 kHz LR24, making it a perfect fit for 2-way home audio speakers with waveguides. This compression driver is not optimized for high SPL.
[1] Distortion measurements. A crossover at 1.1 kHz LR24 promises <1 percent distortion for 96 dB at 1m throughout the passband (HD2):
-> source
[2] Burst decay. The main resonance of the diapragm is pushed to the very high frequencies:
-> source
[3] Detail images of the driver construction courtesy @Zvu:
-> source
[4] Review from audioxpress
https://audioxpress.com/article/peerless-by-tymphany-dfm-2535r00-08-compression-driver
This thread is not to discuss the driver, please use the technical threads instead. If you want to share this group buy on another board, you are welcome. Please send me a message so that I know.
Let's discuss ZM's Good Gemini shunt
The shunt was shown as a brother of Iron pre and Iron pumpkin and was partnered with a capacitance multiplier.
http://www.diyaudio.com/forums/pass-labs/293169-whats-wrong-kiss-boy-19.html#post4883680
I would like some help discussing its Vout range and load current limits to see if it could fit any other projects like the B1, the BA-3 or even digital stuff.
http://www.diyaudio.com/forums/pass-labs/293169-whats-wrong-kiss-boy-19.html#post4883680
I would like some help discussing its Vout range and load current limits to see if it could fit any other projects like the B1, the BA-3 or even digital stuff.
Celestion SL6s restoration: Part III
Celestion SL6s restoration: Part I
Celestion SL6s restoration: Part II
Celestion SL6s restoration: Part III
Some measurements of the speakers with and without crossover:
Celestion SL6s Spkr A impedance no xover red=woofer white=tweeter
Celestion SL6s Spkr B impedance no xover red=woofer white=tweeter
Celestion SL6s Spkr A impedance+xover red=woofer white=tweeter green=speaker
Celestion SL6s Spkr B impedance+xover red=woofer white=tweeter green=speaker
Low frequency nearfield measurement
Red = Mic in baffle plane
White = Mic nearfield, few mm from cone
Celestion SL6s A Low freq resp nearfield & baffle plane
Celestion SL6s B Low freq resp nearfield & baffle plane
Simulations with Basta:
I made a set of simulations based on the measured woofer data, including the baffle response.
- Closed box 10,9 liter
- Damping fill 80%
- Baffle 20x37cm
Basta simulation - spkr A&B freq response-impedance-max output with xover
Basta simulation - spkr A&B freq response-impedance-max output no xover
Basta simulation - spkr A&B freq response-impedance-max output no xover - show group delay
Basta simulation - spkr A&B freq response-impedance-max output no xover - show effect of damping
And just for fun a simulation of the Celstions with the OB sub (see Part I). Probably more a fantasy than a realistic simulation, but it shows that the combination is at least possible.
The OB sun woofer is a Redcatt 154FINDX8-298 15" woofer with TS data from the German Hobby Hifi magazine. Crossover is @120Hz, 24dB/oct Linkwitz-Riley.
Part IV describes my experiences with the Celestions, some comparisons, and at a later data, when the wheather improves, more measurements. I plan to do a full set of FR and polar measurements.
How does a Class A Amp with Ultra-Low THD+N Sound? F5X with PPM THD
My Error-Correction/Composite F5M thought.
By simulation:
1. PPM THD
2. uV output offset
3. H2 dominant
By simulation:
1. PPM THD
2. uV output offset
3. H2 dominant
DIODE ZENER 16V 550MW SOD323F in a bigger Package / Case?
I can't find a bigger case.
I'm working on a Rockford Fosgate R600-4D Prime and need to replace 2 Zener Diodes on the underside of the board D14 & D15 (picture)
While I’m here, I tested everything I could but maybe someone that had this problem where all 4 resistors and the 2 diodes blew. Resistors R59, R60, R61, R62.
With those blown the amp gets really hot to touch. Is there anything I should test?
I'm working on a Rockford Fosgate R600-4D Prime and need to replace 2 Zener Diodes on the underside of the board D14 & D15 (picture)
While I’m here, I tested everything I could but maybe someone that had this problem where all 4 resistors and the 2 diodes blew. Resistors R59, R60, R61, R62.
With those blown the amp gets really hot to touch. Is there anything I should test?
Celestion SL6s restoration: Part I
Celestion SL6s restoration: Part I
Celestion SL6s restoration: Part II
Celestion SL6s restoration: Part III
Some years ago I purchased a pair of Celestion SL6s for €80,- I have listened to them on and off over the last few years, and, although I liked them, the wow factor was mostly absent.
Technically they are in good condition, the same cannot be said for the cabinets.
So I decided to try to repair some of the damage done to the cabinets. I also wanted to mount the crossover outside the cabinet, and create the option of bi-amping or use of an active crossover. Currently it looks like this:
I still have to find a good solution for the lower part of the front.
Another project relating to the Sl6s speakers that I am working on is a dipole subwoofer. The first iteration of that subwoofer uses a single Redcatt 15 inch driver mounted in a 44cm wide frame.
Crossover is active, at 120Hz / 24dB/oct.
Stands
The Celestion SL6s is a bit of a weird speaker in the sense that the optimal listening height of the speaker is not the usual tweeter axis on ear height. Celestion recommended a stand height of 18” (45 cm). That means that from a normal listening distance you can just see the top of the speakers, and ear height is actually slightly above the speaker. The subs have a height of 46 cm, and for normal use I build myself a pair of low stands (Height 45cm/18 inch).
The Tweeters
As can be seen in the pictures the tweeter is in integral part of the frontplate, the dome is actually attached to the back of the frontplate. The magnet can be removed, but you have to be very carefull while doing that. It is easy to damage the voice coil. Likewise I did not try to remove the wiring, because that too seems to me quite risky.
The airtight mounting of the tweeter is done with a putty like sticky substance around the mounting hole between the cabinet front and the metal frontplate of the tweeter. You have to take care when you assemble the tweeter to spread the stuff evenly, to create an airtight fit.
The bolts are corroded, but they are easy to replace.
Dome and magnet separated
The woofers (Celestion T3507 165mm (6.5″) PVC Diaphragm)
The woofer is a well build 6,5” model, designated T…
Celestion SL6s restoration: Part II
Celestion SL6s restoration: Part I
Celestion SL6s restoration: Part II
Celestion SL6s restoration: Part III
TS parameters of the Celestion SL6s woofers
I measured the woofer driver TS parameters with the Clio Pocket. Before I did that I run the drivers for about 36hrs on a 15Hz signal at close to maximum excursion. Just out of curiosity I measured the impedance and TS parameters before and after burn in.
There is some difference between the two woofers, but what do you expect. They are about 40 years old.
Impedance woofers A&B
Spkr B (only) woofer impedance response red=1volt white=3,46volt.
The cabinets
Outside measurements (HxWxD) 376mm x 201mm x 250
Inside measurements (HxWxD) 351mm x 174mm x 195mm
- Baffle thickness 19mm (HDF/MDF)
- Backpanel thickness 12mm (HDF/MDF)
- Sidepanels thickness 13mm multiplex
- Internal brace 19mm (HDF/MDF)
Internal volume of cabinet 1,95 x 1,74 x 3,51 -1 = 10,9 ltr (0,5 ltr for the drivers).
The cabinet is simple, made form a combination of MDF (HDF?) and multiplex. The construction is very rigid, and heavy for such a small cabinet. Note the back panel, which is mounted 22mm inside the cabinet. This is done in order to better supress cabinet resonances.
Cabinet sketch and crossover schematic
The crossover mounted on the inside backpanel, and some of the pulverized damping material.
The crossover
[Correction]
The crossover is simple, with a 12dB/oct lowpass for the woofer and a 18dB/oct highpass for the tweeter.
Woofer=Yellow, Tweeter=White, measurement distance 50cm on tweeter axis, ungated.
Between abott 2k-6k the tweeter shows a falling response of about 6db/oct. This response is compensated in the crossover, resulting in an effectively 12dB/oct crossover response.
Tweeter on axis 50cm 1/12oct smoothing ungated. Red=with xover White=no xover Yellow=drivers out phase Green=drivers in phase.
Freq response tweeter & woofer on axis 50cm 1/12oct smoothing red=tweeter green=woofer with xover
All capacitors are originally (as shown here) Alcaps. I checked the capacitor values.
| Capacitor value | Measured | Δ % |
| 10µF | 11,28 µF | +13% |
| 10µF | 11,44 µF | +14% |
| 6µF | 6,56 µF | +9% |
| 6µF | 6,56 µF | +9% |
| 4µF | 4,28 µF | +7% |
| 4µF | 4,25 µF | +6% |
Not bad for 40 year old capacitors. I still repaced them with Visaton 10µF MKM, and MCaps.
Cabinet damping
The cabinet is almost completely filled with damping material. There are three layers of two types of foam stacked from the backpanel up to the back of the woofer magnet. On top of that there are pieces of foam along the sides up to the baffle. The three top layers of foam, like the green type in the picture below, are in good condition, the bottom layer (of a different type, see the grey foam in the picture below) was essentially reduced to dust, and fell apart when I touched it. This foam layer had to be replaced. It is a sort of reticulated foam, widely used as packaging material, and for water filters.
Part III to follow.
Attachments
-
Celestion SL6s Spkr A impedance no xover red=woofer white=tweeter.png -
Celestion SL6s Spkr B impedance no xover red=woofer white=tweeter.png -
Celestion SL6s Spkr A impedance+xover red=woofer white=tweeter green=speaker.png -
Celestion SL6s Spkr B impedance+xover red=woofer white=tweeter green=speaker.png -
Freq response tweeter & woofer BB on axis 50cm mounted 1-12oct smoothing red=tweeter green=woo...png
BA-3 Amplifier illustrated build guide
Illustrated build guide for the BA-3 amplifier (With complimentary output stage)
The “Burning Amplifier” series is a selection of modular amplifier pieces designed by our technical, spiritual, and menu advisor, Nelson Pass. The pieces can be mixed and matched, used with a range of PSU voltages and scaled up or down as you desire. (The limit, as always with class-A amplifiers being how much heatsink you have…)
There are two gain stages or ‘front-ends’, The BA-1&2 gain stage is a differential pair voltage amplifier with CCS, using some feedback. It can accept a single ended or balanced input. The BA-3 gain stage is a complimentary pair voltage amp with no feedback. There is no ‘better’ between the two stages, just different. You are encouraged to try both and report back your findings.
This guide uses this PCB - P-BAGSN-1V20 - Burning Amplifier Gain Stage for BA-3 (Requires bias boards and output stage; Makes 2 channels; Rev 2.0) - Circuit Boards
The output stages are Complimentary (Push-Pull) and Single-ended. Both these stages can be scaled to hold as many pairs of output Mosfet as you desire, the PCB have provisions for daisy-chain links to add as many boards as you like. (Heatsink and physical area of your case being the limit.)
The Complimentary output (push-pull) is identical to the F4, without the F4’s input buffer, and with the ability to add more Mosfets.
The Single-ended stage is similar to the Aleph amps, the difference being a fixed Constant Current Source instead of the Aleph CCS (which dynamically tracks the output) and the ability to add more mosfets.
This guide uses this PCB set - P-BAC-S4V20 - Burning Amplifier Complementary Bias and Output Set for the BA-2 & BA-3 (Requires a gain stage; Makes 2 channels; Rev 2.0) - Circuit Boards
Either gain stage can be used with either output stage. So not counting the PSU voltage or number of output mosfets there are 4 versions of this amp;
Differential FE, Complimentary output (BA-2)
Differential FE, Single-ended output (BA-1)
Complimentary FE, Complimentary output (BA-3)
Complimentary FE, Single-ended output (BA-3 SE)
Acceptable PSU voltage is from 20-32V, a bipolar supply is needed, you may utilize the diyAudio PSUv3 board or something similar. —
Universal PSU V3 - Circuit Boards
Of course, you will get more output power with higher voltage, at the expense of more heat. (Do you see a trend here…? 🙂 ) There is an upper limit to voltage, approximately 32V, as the input Jfets will start to become very unhappy at voltages much higher. (Of course, you can add a cascode circuit to the front-end to protect the Jfets from higher voltages, but there is no provisions on the PCB to do so.)
Anyway, this guide will show the construction of a BA-3 — a complimentary FE with one PCB of complimentary outputs. PSU will be +/- 32V .
If you haven’t yet, please read this article before continuing. If you have read it, might as well skim over it again, it has lots of great information —
Nelson Pass BA-3 article - Burning Amplifier BA-3 - diyAudio
And as we are using the output stage from the BA-2, this article is quite informative and instructional to read as well -
Nelson Pass BA-2 article - Burning Amplifier BA-2 - diyAudio
Now the one question you will have when reading the articles is this - “How much power does this amp have?” Well, it’s a very fluid design, remember? (So Nelson never said any numbers in his articles, although the information is in the graphs…) But an educated estimate is as follows -
Complimentary output, 24V rails - 25WPC, 8ohm. More into 4ohm
Complimentary output, 32V rails - 40WPC, 8ohm. More into 4ohm.
Single-ended output, 24V rails - 25WPC, 8ohm. Less into 4ohm.
More output devices doesn’t necessarily make more power, but it does provide more current, making difficult speaker loads easier to drive.
Schematic
Front-end
In this schematic note that the Mosfets types are not shown. The suggested pieces are Toshiba 2SK2013 / 2SJ313 (hard to find) and Fairchild FQP3N30 / FQP3P20 (easy to find). I’ve built using both types and can tell no real difference between the Toshiba and the Fairchild. If using Fairchild, use 1K pots for P1, P2. These Mosfets do not need to be matched.
Bias and output.
Schematic Changes (Suggested)
On the Front-end board P1 and P2 can be increased to 1000ohm to help accommodate different Mosfets. (As mentioned in the BA-3 article)
On the bias board I strongly suggest changing R25 to approximately 12K, and P2 to 5K. This will give more range to the circuit to zero the offset, using Fairchild output Mosfets I found it impossible to zero the offset with the original values. Those two minor changes made everything work as designed.
If you have well-matched Mosfets the source resistors (shown as 1.0 ohm 3W) can be reduced to 0.68ohm 3W or 0.47ohm 3W. You will get more output power with smaller source resistors.
Construction
BA-3 gain stage (Front-end) PCB. Note that there are PSU connections (V+, V-, GND) for each channel.
Also raise resistors R10 and R11 as shown, you will need to clip test lead there to set this stage’s bias and DC offset.
As the 5U chassis has enough space to fit the Fe board as shown, I decided to do so, it took only 4 holes drilled in the back. It has the advantage of keeping the input leads very short and away from the power transformer, and also keeping all the PSU wiring located in the same general area of the chassis.
Completed FE board.
FE board wiring. The PSU connections to the FE board are on the back, to keep those wires closer to the chassis. Then can, of course, be in front if you wish.
The completed and installed FE board. Note that the output from the FE to the output boards is not yet connected and shown. (Nor is it visible in this photo, it’s blocked by the bottom of the film caps…)
The diyAudio chassis is modular to the point that it’s easy to loosen a panel and make more room when construction get tight.
Complimentary output PCB.
Complimentary bias PCB.
The two resistor network is 10K+2.2K as I had no 12K in a single resistor. Also visible is a 2K pot in position P2. in the end I used a 5K.
Complimentary board and bias board on 4U heatsink.
Bias board connections - please note the extra washers raising the standoffs and PCB to clear the resistors underneath.
The bias/output connections are visible here - the black and red twisted pair is V+ and V- from the PSU, the white wire is the signal from the FE, labeled “D”, and pink is the speaker output positive (+). Speaker negative (-) is from the PSU GND.
Top view bias board.
It’s a bit busy, but not too bad back at the PSU connections.
Looking into the completed amp.
(Some may be asking, were did the big blue film caps go? Well... In a moment of extreme clumsiness I touched the iron against one of them while soldering another connection, and burnt a hole through. Whoops! Not having a direct replacement, I reached into my box of bits to see what I could come up with, and found some 10uF Silmic II and 0.10uF Rel-Cap film for bypass. That combo sounds great!)
The diyAudio soft start PCB. Not strictly necessary, the CL-60 thermistors in the primary circuit found in the original PSU work great, but this is kinda cool as well… Use the thermistors or the SoftStart.
If you center the LED and use bright blue ones, the glow comes out of the vents without shining out too bright… It's a nice look.
Power Supply
A stereo BA-3 requires a bipolar power supply from (+/-24V) to (+/- 32V). For 24V rails you need a 18V+18V (or 36V Center Tapped) transformer of suitable VA for your number of output devices. (a good rule of thumb is 50VA minimum per stereo pair of devices) and capacitor bank of 60,000 - 80,000uF per rail or more. I.E., a single output board, holding 3pr of Mosfet per channel (12 devices total) will need a 300VA transformer at the minimum. Most people will sure a 400VA. That’s fine. If you have more devices, you must have a bigger transformer. The other rule of thumb is you don’t want more total bias (in watts) than 1/2 of your transformer VA. More about that in the bias section.
The 32V PSU needs a 24V+24V (or 48V Center Tapped) transformer, and PSU capacitance of 60,000 - 80,000uF per rail or more.
Although not the exact PSU as shown in the Nelson Pass article, the diyAudio PSUv3 circuit board can be used to make a suitable power supply for the any of the Pass/Firstwatt amplifiers.
Using the PSUv3 board allows an easy addition of dual diode bridges, which will help keep the transformer mechanical noise to a minimum, and other benefits such as LEDs on each rail, room for (8) capacitors of up to 35mm diameter, the ability to use many different styles of connectors on the board itself, and not to mention the convenience of having everything on one PCB.
The diyAudio universal PSU v3 was made with the requirements of this very amp when it was designed.
The PSU shown in this guide has 50V caps of 18,000uF each, and a 24V+24V, 600VA transformer. (This happens to be the same PSU as used in the F5T guide.)
A build guide for the PSU itself can be found here - http://www.diyaudio.com/forums/powe...circuit-board-v3-illustrated-build-guide.html
Chassis
This is a high-wattage Class-A amplifier. It has lots of excess heat that needs to be dealt with. The 4U chassis can mount one PCB (6 devices) per heatsink. The 5U can mount 2 PCB (12 devices) per heatsink with a little creativity. But with 12 devices you will need to run at a bias amount (slightly reduced) that won’t overwhelm the heatsinks. (No worries, it will still sound fantastic!)
The 5U and 4U Deluxe chassis from the DIY audio store are basically identical except for size and that the 5U heatsinks are 2 pieces per side, so the guide for the 4U chassis is suitable for the 5U as well.
An illustrated guide to building the Deluxe Chassis (4U) can be found here - http://www.diyaudio.com/forums/parts/245959-illustrated-guide-4u-deluxe-chassis.html#post3704810
Testing and Powerup
Bias
Front-end
The procedure for setting bias on the BA-3 FE is almost identical to setting an F5, so this might seem familiar...
The Front-end bias and offset is separate from the output section. Do the FE first. Heck, you don’t even need to connect the output section to bias the FE.
Adjustments (Bias and Offset, set with P1 and P2)
This is easiest with three DMM.
Shorting the input jacks is very helpful, although not strictly necessary.
Before power up, dial pots P1 and P2 to 0 ohms . DON'T adjust P3 during bias
Place one voltmeter (Set to DC volts) across R12 - to observe DC offset
Place a voltmeter (Set to DC volts) across R11 another across R10.
For test - slowly dial up Variac ( presuming that you have one , as man with many skills) up to full mains voltage , observing rail voltage at PSU ....... thinking about max cap voltage ( 25V as in FW ? ) , because with 0 Iq PSU is unloaded and voltage is maxed (It’s useful to have another meter for this…) If nothing is smells bad, and the magic smoke is still in the circuit - leave Variac at full mains ;
IF you don’t have a Variac, you must build a lightbulb mains lead. (with a 25W bulb)
What's important - Iq (measured as the voltage across source resistors; the Mosfet bias) must be very low , offset is irrelevant in this moment .
Now turn one pot one turn ( assuming that you have multiturn pots) then turn other pot one turn. Continue, one turn at a time on each pot until something happens.
Observe voltage across resistors and output DC offset.
Proceed one then second pot , again just one turn
Observe Iq and offset
Again one turn + one turn
Now you are probably in range when you can see which pot is pulling offset in right direction - to 0 . It will feel like one of the pots is controlling the bias on both sides, and the other is controlling the DC offset.
It’s best to increase the bias a bit, and then zero the offset. As you zero the offset you will decrease some of the bias, so it will be two steps forward and one step back. That action is normal.
As you increase the bias and zero the offset, remember to always keep the offset near zero. If you run out of turn on the pots, determine your max bias, with zero offset. (It’s useful for troubleshooting)
Proceed iteratively with pots , while you set - say - 75% of desired bias, with zero offset. Remember, full bias is 1V across R10 and R11, with zero offset BEFORE the capacator. If you measure after the cap there should always be no DC.
Now - put lid on box and let it cook for a while - until you get thermal equilibrium on heatsinks
It's best to use wire/clips to leave those voltmeters in place ;
Open the lid , up bias to - say - 90% of desired one ,while maintaining offset
Put lid on , let it cook.
Check again.
If all is OK - move voltmeters for Bias and offset to other channel and repeat procedure.
Output section -
Do this only after the Front-end is set.
DC offset is adjusted by pot P2 on the bias board. Place a DMM set to DC volts on the speaker outputs and adjust for zero. If you have DC offset that drifts rapidly, it’s likely the TL431 is faulty. Replace.
Bias is adjusted by potentiometer P1 on the bias board. It’s measured by a DMM set to DC volts placed across any of the Mosfet source resistors. To start, set 0.25V measured across the 1.0ohm source resistors.
Use it few days at 90% of desired bias , then check and set to 100%
Remember - temp. equilibrium with lid on is important.
How much bias you can run is determined by a few factors, the most important being heat - the heat of the heatsinks, and the heat of the mosfets themselves.
The simple rules of thumb are -
HEAT = No more than 55C heatsink and 65C Mosfet. (The best place to measure Mosfet temp is pin 2)
TRANSFORMER = The amplifier’s total bias (in Watts) should be no more than 1/2 the VA of your transformer.
How do you determine watts? Simple - measure your bias current, the voltage drop across the 3W source resistors. Let’s say you measure .3V . Divide that by the value of the source resistor. If using 1.0 ohm, your answer is then .3A (.3 / 1 = .3) — but if using 0.47ohm resistors, a voltage drop of .3 is now .64A (.3 / .47 = .637) Back to the example using the 1.0 ohm resistors, multiply by your rail voltage, 32V, so each device will have a bias of 9.6W (.3 * 32 = 9.6) then multiply by the number of devices - 12 in this amp, (12 * 9.6 = 115W)
Setting P3
BEFORE installing and soldering P3 it’s best to adjust the pot so you have equal resistance from pin 1-2 and pin 2-3.
If you didn’t set it, determine how many turns the pot has. Run the pot all the way to one limit (they usually click) and then turn the adjustment the other way for 1/2 of it’s turns. (I.E.,if a 25-turn pot, adjust it 12.5 turns.)
Assuming well matched Jfets the neutral position is going to sound really nice, with 2nd harmonic dominant at the 1W level. IF you have access to a distortion analyzer, or a high-resolution FFT (or both…) give the amp a 1K test sine wave that outputs 1W into your load resistor. Then adjust P3 as necessary for the harmonics you prefer. If you adjust for minimum THD, you will likely have nulled out most of the 2nd harmonic and made it 3rd dominant, which in my opinion makes it very fast and clean, at the expense of soul. YMMV.
Anyway, if you DON’T have a distortion analyzer or similar, take careful notes and turn the pot a few turns (or more) in whatever direction you want and see what it sounds like. It’s a subtle change, but I think you will sense something. You can refer to you notes and see where you like the pot the best. And if you ever get lost, set it back to neutral, (with the power off) just bottom the pot in one direction and set it back to 1/2 it’s travel.
Lightbulb Mains lead notes -
If the bulb ever turns on and stays bright, you probably have a short.
Normal operation when turning on a cold amp will have the bulb glow bright for a second or two, then dim, perhaps off. (this is the capacitors charging, then full)
As you increase the bias of the amp the bulb will glow brighter, and this is linear with the bias amount. A fully biased amp can get the bulb to glow very bright.
You cannot set full bias with the bulb in place - as it increases the bulb will glow more, limiting the voltage to the amp and all the readings will be wrong compared to when the bulb lead is out.
You can, however, set the initial bias with the bulb in place. Start the procedure, turn the pots until something happens, and set, at maximum, 0.1V across the source resistors and zero offset. Getting the pots started this way is a good idea. Remember, this is with a reduced voltage, and the pots will make the circuit draw MUCH more bias when the normal mains lead in used. Expect to measure 0.2V or more with a normal cord. Continue biasing in small steps, always trying to keep the offset near zero.
The “Burning Amplifier” series is a selection of modular amplifier pieces designed by our technical, spiritual, and menu advisor, Nelson Pass. The pieces can be mixed and matched, used with a range of PSU voltages and scaled up or down as you desire. (The limit, as always with class-A amplifiers being how much heatsink you have…)
There are two gain stages or ‘front-ends’, The BA-1&2 gain stage is a differential pair voltage amplifier with CCS, using some feedback. It can accept a single ended or balanced input. The BA-3 gain stage is a complimentary pair voltage amp with no feedback. There is no ‘better’ between the two stages, just different. You are encouraged to try both and report back your findings.
This guide uses this PCB - P-BAGSN-1V20 - Burning Amplifier Gain Stage for BA-3 (Requires bias boards and output stage; Makes 2 channels; Rev 2.0) - Circuit Boards
The output stages are Complimentary (Push-Pull) and Single-ended. Both these stages can be scaled to hold as many pairs of output Mosfet as you desire, the PCB have provisions for daisy-chain links to add as many boards as you like. (Heatsink and physical area of your case being the limit.)
The Complimentary output (push-pull) is identical to the F4, without the F4’s input buffer, and with the ability to add more Mosfets.
The Single-ended stage is similar to the Aleph amps, the difference being a fixed Constant Current Source instead of the Aleph CCS (which dynamically tracks the output) and the ability to add more mosfets.
This guide uses this PCB set - P-BAC-S4V20 - Burning Amplifier Complementary Bias and Output Set for the BA-2 & BA-3 (Requires a gain stage; Makes 2 channels; Rev 2.0) - Circuit Boards
Either gain stage can be used with either output stage. So not counting the PSU voltage or number of output mosfets there are 4 versions of this amp;
Differential FE, Complimentary output (BA-2)
Differential FE, Single-ended output (BA-1)
Complimentary FE, Complimentary output (BA-3)
Complimentary FE, Single-ended output (BA-3 SE)
Acceptable PSU voltage is from 20-32V, a bipolar supply is needed, you may utilize the diyAudio PSUv3 board or something similar. —
Universal PSU V3 - Circuit Boards
Of course, you will get more output power with higher voltage, at the expense of more heat. (Do you see a trend here…? 🙂 ) There is an upper limit to voltage, approximately 32V, as the input Jfets will start to become very unhappy at voltages much higher. (Of course, you can add a cascode circuit to the front-end to protect the Jfets from higher voltages, but there is no provisions on the PCB to do so.)
Anyway, this guide will show the construction of a BA-3 — a complimentary FE with one PCB of complimentary outputs. PSU will be +/- 32V .
If you haven’t yet, please read this article before continuing. If you have read it, might as well skim over it again, it has lots of great information —
Nelson Pass BA-3 article - Burning Amplifier BA-3 - diyAudio
And as we are using the output stage from the BA-2, this article is quite informative and instructional to read as well -
Nelson Pass BA-2 article - Burning Amplifier BA-2 - diyAudio
Now the one question you will have when reading the articles is this - “How much power does this amp have?” Well, it’s a very fluid design, remember? (So Nelson never said any numbers in his articles, although the information is in the graphs…) But an educated estimate is as follows -
Complimentary output, 24V rails - 25WPC, 8ohm. More into 4ohm
Complimentary output, 32V rails - 40WPC, 8ohm. More into 4ohm.
Single-ended output, 24V rails - 25WPC, 8ohm. Less into 4ohm.
More output devices doesn’t necessarily make more power, but it does provide more current, making difficult speaker loads easier to drive.
Schematic
Front-end
In this schematic note that the Mosfets types are not shown. The suggested pieces are Toshiba 2SK2013 / 2SJ313 (hard to find) and Fairchild FQP3N30 / FQP3P20 (easy to find). I’ve built using both types and can tell no real difference between the Toshiba and the Fairchild. If using Fairchild, use 1K pots for P1, P2. These Mosfets do not need to be matched.
Bias and output.
Schematic Changes (Suggested)
On the Front-end board P1 and P2 can be increased to 1000ohm to help accommodate different Mosfets. (As mentioned in the BA-3 article)
On the bias board I strongly suggest changing R25 to approximately 12K, and P2 to 5K. This will give more range to the circuit to zero the offset, using Fairchild output Mosfets I found it impossible to zero the offset with the original values. Those two minor changes made everything work as designed.
If you have well-matched Mosfets the source resistors (shown as 1.0 ohm 3W) can be reduced to 0.68ohm 3W or 0.47ohm 3W. You will get more output power with smaller source resistors.
Construction
BA-3 gain stage (Front-end) PCB. Note that there are PSU connections (V+, V-, GND) for each channel.
Also raise resistors R10 and R11 as shown, you will need to clip test lead there to set this stage’s bias and DC offset.
As the 5U chassis has enough space to fit the Fe board as shown, I decided to do so, it took only 4 holes drilled in the back. It has the advantage of keeping the input leads very short and away from the power transformer, and also keeping all the PSU wiring located in the same general area of the chassis.
Completed FE board.
FE board wiring. The PSU connections to the FE board are on the back, to keep those wires closer to the chassis. Then can, of course, be in front if you wish.
The completed and installed FE board. Note that the output from the FE to the output boards is not yet connected and shown. (Nor is it visible in this photo, it’s blocked by the bottom of the film caps…)
The diyAudio chassis is modular to the point that it’s easy to loosen a panel and make more room when construction get tight.
Complimentary output PCB.
Complimentary bias PCB.
The two resistor network is 10K+2.2K as I had no 12K in a single resistor. Also visible is a 2K pot in position P2. in the end I used a 5K.
Complimentary board and bias board on 4U heatsink.
Bias board connections - please note the extra washers raising the standoffs and PCB to clear the resistors underneath.
The bias/output connections are visible here - the black and red twisted pair is V+ and V- from the PSU, the white wire is the signal from the FE, labeled “D”, and pink is the speaker output positive (+). Speaker negative (-) is from the PSU GND.
Top view bias board.
It’s a bit busy, but not too bad back at the PSU connections.
Looking into the completed amp.
(Some may be asking, were did the big blue film caps go? Well... In a moment of extreme clumsiness I touched the iron against one of them while soldering another connection, and burnt a hole through. Whoops! Not having a direct replacement, I reached into my box of bits to see what I could come up with, and found some 10uF Silmic II and 0.10uF Rel-Cap film for bypass. That combo sounds great!)
The diyAudio soft start PCB. Not strictly necessary, the CL-60 thermistors in the primary circuit found in the original PSU work great, but this is kinda cool as well… Use the thermistors or the SoftStart.
If you center the LED and use bright blue ones, the glow comes out of the vents without shining out too bright… It's a nice look.
Power Supply
A stereo BA-3 requires a bipolar power supply from (+/-24V) to (+/- 32V). For 24V rails you need a 18V+18V (or 36V Center Tapped) transformer of suitable VA for your number of output devices. (a good rule of thumb is 50VA minimum per stereo pair of devices) and capacitor bank of 60,000 - 80,000uF per rail or more. I.E., a single output board, holding 3pr of Mosfet per channel (12 devices total) will need a 300VA transformer at the minimum. Most people will sure a 400VA. That’s fine. If you have more devices, you must have a bigger transformer. The other rule of thumb is you don’t want more total bias (in watts) than 1/2 of your transformer VA. More about that in the bias section.
The 32V PSU needs a 24V+24V (or 48V Center Tapped) transformer, and PSU capacitance of 60,000 - 80,000uF per rail or more.
Although not the exact PSU as shown in the Nelson Pass article, the diyAudio PSUv3 circuit board can be used to make a suitable power supply for the any of the Pass/Firstwatt amplifiers.
Using the PSUv3 board allows an easy addition of dual diode bridges, which will help keep the transformer mechanical noise to a minimum, and other benefits such as LEDs on each rail, room for (8) capacitors of up to 35mm diameter, the ability to use many different styles of connectors on the board itself, and not to mention the convenience of having everything on one PCB.
The diyAudio universal PSU v3 was made with the requirements of this very amp when it was designed.
The PSU shown in this guide has 50V caps of 18,000uF each, and a 24V+24V, 600VA transformer. (This happens to be the same PSU as used in the F5T guide.)
A build guide for the PSU itself can be found here - http://www.diyaudio.com/forums/powe...circuit-board-v3-illustrated-build-guide.html
Chassis
This is a high-wattage Class-A amplifier. It has lots of excess heat that needs to be dealt with. The 4U chassis can mount one PCB (6 devices) per heatsink. The 5U can mount 2 PCB (12 devices) per heatsink with a little creativity. But with 12 devices you will need to run at a bias amount (slightly reduced) that won’t overwhelm the heatsinks. (No worries, it will still sound fantastic!)
The 5U and 4U Deluxe chassis from the DIY audio store are basically identical except for size and that the 5U heatsinks are 2 pieces per side, so the guide for the 4U chassis is suitable for the 5U as well.
An illustrated guide to building the Deluxe Chassis (4U) can be found here - http://www.diyaudio.com/forums/parts/245959-illustrated-guide-4u-deluxe-chassis.html#post3704810
Testing and Powerup
Bias
Front-end
The procedure for setting bias on the BA-3 FE is almost identical to setting an F5, so this might seem familiar...
The Front-end bias and offset is separate from the output section. Do the FE first. Heck, you don’t even need to connect the output section to bias the FE.
Adjustments (Bias and Offset, set with P1 and P2)
This is easiest with three DMM.
Shorting the input jacks is very helpful, although not strictly necessary.
Before power up, dial pots P1 and P2 to 0 ohms . DON'T adjust P3 during bias
Place one voltmeter (Set to DC volts) across R12 - to observe DC offset
Place a voltmeter (Set to DC volts) across R11 another across R10.
For test - slowly dial up Variac ( presuming that you have one , as man with many skills) up to full mains voltage , observing rail voltage at PSU ....... thinking about max cap voltage ( 25V as in FW ? ) , because with 0 Iq PSU is unloaded and voltage is maxed (It’s useful to have another meter for this…) If nothing is smells bad, and the magic smoke is still in the circuit - leave Variac at full mains ;
IF you don’t have a Variac, you must build a lightbulb mains lead. (with a 25W bulb)
What's important - Iq (measured as the voltage across source resistors; the Mosfet bias) must be very low , offset is irrelevant in this moment .
Now turn one pot one turn ( assuming that you have multiturn pots) then turn other pot one turn. Continue, one turn at a time on each pot until something happens.
Observe voltage across resistors and output DC offset.
Proceed one then second pot , again just one turn
Observe Iq and offset
Again one turn + one turn
Now you are probably in range when you can see which pot is pulling offset in right direction - to 0 . It will feel like one of the pots is controlling the bias on both sides, and the other is controlling the DC offset.
It’s best to increase the bias a bit, and then zero the offset. As you zero the offset you will decrease some of the bias, so it will be two steps forward and one step back. That action is normal.
As you increase the bias and zero the offset, remember to always keep the offset near zero. If you run out of turn on the pots, determine your max bias, with zero offset. (It’s useful for troubleshooting)
Proceed iteratively with pots , while you set - say - 75% of desired bias, with zero offset. Remember, full bias is 1V across R10 and R11, with zero offset BEFORE the capacator. If you measure after the cap there should always be no DC.
Now - put lid on box and let it cook for a while - until you get thermal equilibrium on heatsinks
It's best to use wire/clips to leave those voltmeters in place ;
Open the lid , up bias to - say - 90% of desired one ,while maintaining offset
Put lid on , let it cook.
Check again.
If all is OK - move voltmeters for Bias and offset to other channel and repeat procedure.
Output section -
Do this only after the Front-end is set.
DC offset is adjusted by pot P2 on the bias board. Place a DMM set to DC volts on the speaker outputs and adjust for zero. If you have DC offset that drifts rapidly, it’s likely the TL431 is faulty. Replace.
Bias is adjusted by potentiometer P1 on the bias board. It’s measured by a DMM set to DC volts placed across any of the Mosfet source resistors. To start, set 0.25V measured across the 1.0ohm source resistors.
Use it few days at 90% of desired bias , then check and set to 100%
Remember - temp. equilibrium with lid on is important.
How much bias you can run is determined by a few factors, the most important being heat - the heat of the heatsinks, and the heat of the mosfets themselves.
The simple rules of thumb are -
HEAT = No more than 55C heatsink and 65C Mosfet. (The best place to measure Mosfet temp is pin 2)
TRANSFORMER = The amplifier’s total bias (in Watts) should be no more than 1/2 the VA of your transformer.
How do you determine watts? Simple - measure your bias current, the voltage drop across the 3W source resistors. Let’s say you measure .3V . Divide that by the value of the source resistor. If using 1.0 ohm, your answer is then .3A (.3 / 1 = .3) — but if using 0.47ohm resistors, a voltage drop of .3 is now .64A (.3 / .47 = .637) Back to the example using the 1.0 ohm resistors, multiply by your rail voltage, 32V, so each device will have a bias of 9.6W (.3 * 32 = 9.6) then multiply by the number of devices - 12 in this amp, (12 * 9.6 = 115W)
Setting P3
BEFORE installing and soldering P3 it’s best to adjust the pot so you have equal resistance from pin 1-2 and pin 2-3.
If you didn’t set it, determine how many turns the pot has. Run the pot all the way to one limit (they usually click) and then turn the adjustment the other way for 1/2 of it’s turns. (I.E.,if a 25-turn pot, adjust it 12.5 turns.)
Assuming well matched Jfets the neutral position is going to sound really nice, with 2nd harmonic dominant at the 1W level. IF you have access to a distortion analyzer, or a high-resolution FFT (or both…) give the amp a 1K test sine wave that outputs 1W into your load resistor. Then adjust P3 as necessary for the harmonics you prefer. If you adjust for minimum THD, you will likely have nulled out most of the 2nd harmonic and made it 3rd dominant, which in my opinion makes it very fast and clean, at the expense of soul. YMMV.
Anyway, if you DON’T have a distortion analyzer or similar, take careful notes and turn the pot a few turns (or more) in whatever direction you want and see what it sounds like. It’s a subtle change, but I think you will sense something. You can refer to you notes and see where you like the pot the best. And if you ever get lost, set it back to neutral, (with the power off) just bottom the pot in one direction and set it back to 1/2 it’s travel.
Lightbulb Mains lead notes -
If the bulb ever turns on and stays bright, you probably have a short.
Normal operation when turning on a cold amp will have the bulb glow bright for a second or two, then dim, perhaps off. (this is the capacitors charging, then full)
As you increase the bias of the amp the bulb will glow brighter, and this is linear with the bias amount. A fully biased amp can get the bulb to glow very bright.
You cannot set full bias with the bulb in place - as it increases the bulb will glow more, limiting the voltage to the amp and all the readings will be wrong compared to when the bulb lead is out.
You can, however, set the initial bias with the bulb in place. Start the procedure, turn the pots until something happens, and set, at maximum, 0.1V across the source resistors and zero offset. Getting the pots started this way is a good idea. Remember, this is with a reduced voltage, and the pots will make the circuit draw MUCH more bias when the normal mains lead in used. Expect to measure 0.2V or more with a normal cord. Continue biasing in small steps, always trying to keep the offset near zero.
Oscillation into voltage regulator of my new NAP 250 design.
- By cristobool
- Solid State
- 41 Replies
Hello everyone, these last months I started designing a more accomplished NAP250 clone, I may have been too ambitious and suddenly I end up with a small problem of oscillation of the main regulator.
I respected the Naim audio diagram with the difference that I placed the amplifier and the regulator (NAPS) on the same PCB, routing level it was complicated to do.
After wanting to improve the amplifier I replaced the MPSA56/06 transistor references with ZTX753/653 which are more robust
the drivers and output transistors were also replaced by
TTC3710B/TTA1452B
and MJW18020 at the output.
The output filtering capacities are at good esr for stability and those at the input too.
everything else works fine the amp the phase compensation etc I even added the TGM10 speaker protection which works and also a front regulator (like the NAP250 DR) but for the moment I dismantled the front regulator to focus on the NAPS which is faulty.
I specify that on laboratory power supply everything worked without problem and the oscillation was therefore not present, I think it is the ripple of the symmetrical power supply which is not supported by the regulator.
do you have any ideas as to the cause of the problem compared to the original design? or do you have a modification to make that could stabilize this problem?
thank you in advance I put you pictures of scope and the new design.
the oscillation is a 150Khz component which makes 100 mv on the negative rail and 50 mv on the positive rail.
I respected the Naim audio diagram with the difference that I placed the amplifier and the regulator (NAPS) on the same PCB, routing level it was complicated to do.
After wanting to improve the amplifier I replaced the MPSA56/06 transistor references with ZTX753/653 which are more robust
the drivers and output transistors were also replaced by
TTC3710B/TTA1452B
and MJW18020 at the output.
The output filtering capacities are at good esr for stability and those at the input too.
everything else works fine the amp the phase compensation etc I even added the TGM10 speaker protection which works and also a front regulator (like the NAP250 DR) but for the moment I dismantled the front regulator to focus on the NAPS which is faulty.
I specify that on laboratory power supply everything worked without problem and the oscillation was therefore not present, I think it is the ripple of the symmetrical power supply which is not supported by the regulator.
do you have any ideas as to the cause of the problem compared to the original design? or do you have a modification to make that could stabilize this problem?
thank you in advance I put you pictures of scope and the new design.
the oscillation is a 150Khz component which makes 100 mv on the negative rail and 50 mv on the positive rail.
Attachments
Making surround speakers with Markaudio chn50
- By Audientid14
- Full Range
- 5 Replies
I have made two surround ”eggs” to complement my chn110 tower speakers , using the similar looking but much smaller chn50 driver in a small cabinet.
Two IKEA 12 cm wooden bowls and a 3 inch 22mm Mdf ring was glued and painted in black. I used a round black cable and making the drilled hole in the speakers very tight so they dont need any connectors. Inside there is sheeps wool and no crossover at all.
These speakers will be mounted on two speaker stands with a round base.
The reason I made these speakers is the new software in WiiM ultra , allowing dolby digital 4.0 with the help of my older WiiM PRO and my Hypex ncore 125 amplifier.
Two IKEA 12 cm wooden bowls and a 3 inch 22mm Mdf ring was glued and painted in black. I used a round black cable and making the drilled hole in the speakers very tight so they dont need any connectors. Inside there is sheeps wool and no crossover at all.
These speakers will be mounted on two speaker stands with a round base.
The reason I made these speakers is the new software in WiiM ultra , allowing dolby digital 4.0 with the help of my older WiiM PRO and my Hypex ncore 125 amplifier.
6V6 amp PP
- By mrpunkk
- Tubes / Valves
- 22 Replies
Hi friends, a while back I built this amp for a friend(with some changes). He's been using it for several years without any issues. A few weeks ago, he told me he was hearing a noise on the right channel. I thought it was the 6v6s running out. I set up the oscilloscope and detected a noise/oscillation in the negative part of the sine wave that I can't detect. Can you give me any clues on how to locate the fault? Could it be the OPT? I've already tried another 12ax7 and re-soldered it.
The red marks are where I placed the oscilloscope and found the noise.
The other triode of the 12ax7 and the other 6v6 work ok, to eliminate the potentiometer.
I inverted the 6v6 too.
thanx a lot guys!!
https://diyaudioprojects.com/Schematics/DIY-Push-Pull-PP-6V6-Tube-Amplifier/
The red marks are where I placed the oscilloscope and found the noise.
The other triode of the 12ax7 and the other 6v6 work ok, to eliminate the potentiometer.
I inverted the 6v6 too.
thanx a lot guys!!
https://diyaudioprojects.com/Schematics/DIY-Push-Pull-PP-6V6-Tube-Amplifier/