T25A Simple Waveguide Profile
Recently @hifijim started a new project involving the Bliesma T25A tweeter, as part of the discussion I offered to see if a simple small waveguide could be simulated. Jim has decided against the use of a waveguide for perfectly understandable reasons. I don't have a T25A myself and so I haven't created a printable model of the profile to test. There was some interest shown in that thread for the waveguide profile to be posted in a separate thread, so here it is.
The Bliesma aluminium drivers are very tall and require a different profile than many modern waveguides aim for in order to avoid ugly cancellations in the very high frequency range. I tried a number of variations on a theme in Ath to see what I could get, but it was not easy to find a profile that did not have some kind of downside to it.
I've simulated many CAD drawn profiles for the T25A in the past and so that is the route I tried next. This should hardly come as news or any kind of discovery as it has been known for a long time that dome tweeters almost always work in a waveguide that uses a section of a circular radius for it's profile. This does not have as dramatic of an effect on the directivity as OS or other proflies can have, but it is that property of not doing too much that allows it to work almost as a universal profile.
It is very simple to draw in a CAD program. I use Fusion and will outline how to use that program to draw it, but the principal could be applied to any other program.
This waveguide is thin at 6mm and relatively small at 104mm in diameter, similar to a standard tweeter faceplate.
I first draw a circle on the XZ plane that represents the throat, in this case it is 29.7mm, using a slightly higher value of 30mm might be preferable depending on the properties of the material being used to print it.
A new sketch is drawn on the XY plane and the previous circle is projected into this sketch. I draw a construction line straight up at the depth of the waveguide in this case 6mm. I then draw another line across at a 90 degree angle the distance of half the overall diameter in this case 52mm. I then draw a 3 point arc between the projected throat, the outer point of the waveguide profile and the last point just needs to be below the top construction line. With practice you can place it so that tangency is already enforced, but if not use the sketch constraints to make the 3 point arc tangent to the top construction line. You can check if this has worked by extending the arc all the way around until it becomes a circle. In this case the 3 point arc as drawn has a radius of 118.01mm.
The centre point of the circle that is the radius can be see by zooming out the sketch, it is highlighted in yellow
The same principal could be used to create a deeper and larger version of the same thing, there will then be a bigger effect on the overall directivity. This may not be a good thing for the T25A, but if the same ratio is kept between depth and outer diameter I would imagine it could be scaled up without creating negative interference. I haven't tested this so I cannot say exactly what will happen.
I have attached the surface profile as a zipped step file in case anyone wants to use it as is to create their own printable model.
I have attached the simulation outputs based on Jim's baffle. It is more consistent and even than a bare driver and given the size constraints, it fit's on the same diameter as the driver or can be made to. These are non normalized and show 1500 to 15K 0 to 90 degrees in 10 degree steps. The response is pretty much within 1 or 2 dB 0 to 40 degrees and is an even 10 dB down across the board at 90 degrees vs 0.
There is diffraction on axis because this is a BEM model with fully reflective boundaries. All sharp edges and creases on the baffle of which there are a few that are also symmetric show the worst case scenario. A real wooden baffle with smoothed edges and a less symmetric profile would offset this to some extent.
By 15 degrees off axis the response is a pretty smooth downslope
The Bliesma aluminium drivers are very tall and require a different profile than many modern waveguides aim for in order to avoid ugly cancellations in the very high frequency range. I tried a number of variations on a theme in Ath to see what I could get, but it was not easy to find a profile that did not have some kind of downside to it.
I've simulated many CAD drawn profiles for the T25A in the past and so that is the route I tried next. This should hardly come as news or any kind of discovery as it has been known for a long time that dome tweeters almost always work in a waveguide that uses a section of a circular radius for it's profile. This does not have as dramatic of an effect on the directivity as OS or other proflies can have, but it is that property of not doing too much that allows it to work almost as a universal profile.
It is very simple to draw in a CAD program. I use Fusion and will outline how to use that program to draw it, but the principal could be applied to any other program.
This waveguide is thin at 6mm and relatively small at 104mm in diameter, similar to a standard tweeter faceplate.
I first draw a circle on the XZ plane that represents the throat, in this case it is 29.7mm, using a slightly higher value of 30mm might be preferable depending on the properties of the material being used to print it.
A new sketch is drawn on the XY plane and the previous circle is projected into this sketch. I draw a construction line straight up at the depth of the waveguide in this case 6mm. I then draw another line across at a 90 degree angle the distance of half the overall diameter in this case 52mm. I then draw a 3 point arc between the projected throat, the outer point of the waveguide profile and the last point just needs to be below the top construction line. With practice you can place it so that tangency is already enforced, but if not use the sketch constraints to make the 3 point arc tangent to the top construction line. You can check if this has worked by extending the arc all the way around until it becomes a circle. In this case the 3 point arc as drawn has a radius of 118.01mm.
The centre point of the circle that is the radius can be see by zooming out the sketch, it is highlighted in yellow
The same principal could be used to create a deeper and larger version of the same thing, there will then be a bigger effect on the overall directivity. This may not be a good thing for the T25A, but if the same ratio is kept between depth and outer diameter I would imagine it could be scaled up without creating negative interference. I haven't tested this so I cannot say exactly what will happen.
I have attached the surface profile as a zipped step file in case anyone wants to use it as is to create their own printable model.
I have attached the simulation outputs based on Jim's baffle. It is more consistent and even than a bare driver and given the size constraints, it fit's on the same diameter as the driver or can be made to. These are non normalized and show 1500 to 15K 0 to 90 degrees in 10 degree steps. The response is pretty much within 1 or 2 dB 0 to 40 degrees and is an even 10 dB down across the board at 90 degrees vs 0.
There is diffraction on axis because this is a BEM model with fully reflective boundaries. All sharp edges and creases on the baffle of which there are a few that are also symmetric show the worst case scenario. A real wooden baffle with smoothed edges and a less symmetric profile would offset this to some extent.
By 15 degrees off axis the response is a pretty smooth downslope
Attachments
Yet Another Transistor Phono Stage, or Going crazy with discrete opamps
- Analogue Source
- 10 Replies
Some time ago I had an idea to build a discrete phono stage using bipolar power supplies, but did not really know where to start, so I decided to implement it as a discrete opamp.
I started with this image from Wikipedia showing the basic topology of a discrete opamp with complementary LTPs at the input:
This was the first version of my discrete opamp:
To my surprise, the simulation worked at the first try, but it was not particularly impressive. So I started thinking about improving its linearity. Douglas Self in Small Signal Audio Design says that the two things that help the most are:
1) unloading the VAS by implementing an output stage;
b) improving the linearity of the input stage.
My next step was to add an output stage. Dominant pole compensation was moved from the input differential pairs to VAS (screenshot from QUCS):
These changes, together with adding emitter resistors to the LTPs, reduced distortion by a factor of 15, but it was still not good enough. I ended up replacing tail resistors with constant current sources. Also had to tackle some small capacitors onto the LTPs to make the circuit unity gain stable.
This was almost the final result (shown here with the RIAA feedback network):
I showed it to a friend who is an electrical engineer and a passionate audiophile and he told me that it looks "like an improved version of Acurus P10"
I was really disappointed because I had been so proud of myself...
Anyhow, I designed a small one-channel PCB. Here it is shown built as a simple flat gain stage (no RIAA network):
I later configured it as a unity gain buffer by removing R14 and confirmed that it was, in fact, unity gain stable. I measured 0.0006% THD at 1kHz into 2K load, but my audio interface is an ancient EMU 0202USB which is only capable of about 0.0005% THD in loopback. Which means that the performance of this gain stage is probably somewhat better than that, but since I can't measure it, I am not going to make any claims about it. I did not match the transistors in LTPs by Vbe and hFE, instead I simply took 6 transistors in a row from the same ammo pack for both NPNs and PNPs. The worst DC offset at the input that I measured was about 15mV after an hour, which is definitely not fantastic, but also not a huge problem (at least not to the extent that it would interfere with the normal functioning of the circuit).
Two channels configured as a phono preamp, powered from a very audiophile PSU, and with suitably high-end wiring to boot...
I won't show all measurements because I can't get rid of a ground loop somewhere, but this is the frequency response (measured using R. Williamson's reverse RIAA network):
It works well and sounds great!
Later I thought: "Gee, this discrete opamp thingamajig seems to perform rather well, why not try using it as a regular opamp?" The result was this terrible little thing, with more robust output transistors and the optional ability to adjust quiescent current in the output stage...
To be continued...
I started with this image from Wikipedia showing the basic topology of a discrete opamp with complementary LTPs at the input:
This was the first version of my discrete opamp:
To my surprise, the simulation worked at the first try, but it was not particularly impressive. So I started thinking about improving its linearity. Douglas Self in Small Signal Audio Design says that the two things that help the most are:
1) unloading the VAS by implementing an output stage;
b) improving the linearity of the input stage.
My next step was to add an output stage. Dominant pole compensation was moved from the input differential pairs to VAS (screenshot from QUCS):
These changes, together with adding emitter resistors to the LTPs, reduced distortion by a factor of 15, but it was still not good enough. I ended up replacing tail resistors with constant current sources. Also had to tackle some small capacitors onto the LTPs to make the circuit unity gain stable.
This was almost the final result (shown here with the RIAA feedback network):
I showed it to a friend who is an electrical engineer and a passionate audiophile and he told me that it looks "like an improved version of Acurus P10"
I was really disappointed because I had been so proud of myself...Anyhow, I designed a small one-channel PCB. Here it is shown built as a simple flat gain stage (no RIAA network):
I later configured it as a unity gain buffer by removing R14 and confirmed that it was, in fact, unity gain stable. I measured 0.0006% THD at 1kHz into 2K load, but my audio interface is an ancient EMU 0202USB which is only capable of about 0.0005% THD in loopback. Which means that the performance of this gain stage is probably somewhat better than that, but since I can't measure it, I am not going to make any claims about it. I did not match the transistors in LTPs by Vbe and hFE, instead I simply took 6 transistors in a row from the same ammo pack for both NPNs and PNPs. The worst DC offset at the input that I measured was about 15mV after an hour, which is definitely not fantastic, but also not a huge problem (at least not to the extent that it would interfere with the normal functioning of the circuit).
Two channels configured as a phono preamp, powered from a very audiophile PSU, and with suitably high-end wiring to boot...
I won't show all measurements because I can't get rid of a ground loop somewhere, but this is the frequency response (measured using R. Williamson's reverse RIAA network):
It works well and sounds great!
Later I thought: "Gee, this discrete opamp thingamajig seems to perform rather well, why not try using it as a regular opamp?" The result was this terrible little thing, with more robust output transistors and the optional ability to adjust quiescent current in the output stage...
To be continued...
TKD 2P65CS stepped attenuator
One used TKD 2P65CS 40-step attenuator for sale.
20k ohm, stereo version. Non-magnetic construction.
Asking $300 + shipping
20k ohm, stereo version. Non-magnetic construction.
Asking $300 + shipping
Digital tuner noise
- By RomesINMil
- Instruments and Amps
- 9 Replies
Howdy tubesters!
So I got my first amp working and used a Crate.... what is it called, the wood / composite box with the speakers and the amp... its fine...
Anyway it had a stand alone digital tuner that I incorporated by powering it with the 5v heater line and Cap/Diode voltage multiplier. The lines from the tuner were three, black red and white. I assumed the white is audio in since I could not find any documentation since it is probs manufactured specially.
I tapped the the guitar jack with a 33k resistor and sheilded wire grounded by the jack to the female 8mm mounted on the bottom / back of the chassis (******* weird *** spelling for a word). Problem is when I connect the male to the chassis mounted one a terrible noise is present in the signal.
I have tried a standalone transformer for the thing, and noticed that just having the ****** plugged in to the chassis with no power it makes the noise.
And you will notice at an attempt to smooth the signal with bead and caps....
Any advise would be very much welcomed.
Thanks!
Login to view embedded media
So I got my first amp working and used a Crate.... what is it called, the wood / composite box with the speakers and the amp... its fine...
Anyway it had a stand alone digital tuner that I incorporated by powering it with the 5v heater line and Cap/Diode voltage multiplier. The lines from the tuner were three, black red and white. I assumed the white is audio in since I could not find any documentation since it is probs manufactured specially.
I tapped the the guitar jack with a 33k resistor and sheilded wire grounded by the jack to the female 8mm mounted on the bottom / back of the chassis (******* weird *** spelling for a word). Problem is when I connect the male to the chassis mounted one a terrible noise is present in the signal.
I have tried a standalone transformer for the thing, and noticed that just having the ****** plugged in to the chassis with no power it makes the noise.
And you will notice at an attempt to smooth the signal with bead and caps....
Any advise would be very much welcomed.
Thanks!
OCMOS FET
I have seen a schema of optically coupled MOSFET ciruits, as a solid state reay. I saw that Renesas has astory line about isolated mosfet drivers. Some vendors focus on 100kV switching. . . But we need automotive quality like Toshiba's TLP570xH IGBT & MOSFET Isolated Gate Driver.
While this picture assumes the mosfets are inside the package,
the following is a driver that needs external Mosfets: VOM1271.
Just. Four pins!
Drive a single or back-to-back N-mosfets (sources combined).
"Unlike conventional MOSFET drivers, which require an external power supply to provide VCC and or VDD rails to the driver itself, the VOM1271 obtains all the required current [=voltage] to drive its internal circuitry from the LED current on the low voltage primary side of the isolation barrier." The cell generates the voltage to turn on the mosfet, up to 8.4V.
The essence is that the driver signal is totally isolated from a power line. useful for switching power lines. Or. For instance as speaker relay, as it can handle AC. They handle 40A both ways. With <5mOhm resistance, and "<-90dB distortion".
My interest is as follows: I want to have an amplifier with on the one hand an F4 (no gain, no pain) and also an F8 (my version of a SIT follower, no gain, lots of pain). [My F8 is a mash-up of for example ZM's BJT version; I choose the nice 2SJ74 as input, maybe should call it J2/F8 to make things more complex; See attached. 2.]. . . Essential: Same power lines as F4 (25V).
but this board is not isolated. GND is common ground. But it probably is bidirectional, having two fets back to back. So that one extra component is needed.
An example of a driver that is isolated, is: VOM1271 (Vishay) = Photovoltaic MOSFET Driver With Integrated Fast Turn-Off, for Solid-State Relay. There must be more.
the following is a driver that needs external Mosfets: VOM1271.
"Unlike conventional MOSFET drivers, which require an external power supply to provide VCC and or VDD rails to the driver itself, the VOM1271 obtains all the required current [=voltage] to drive its internal circuitry from the LED current on the low voltage primary side of the isolation barrier." The cell generates the voltage to turn on the mosfet, up to 8.4V.
The essence is that the driver signal is totally isolated from a power line. useful for switching power lines. Or. For instance as speaker relay, as it can handle AC. They handle 40A both ways. With <5mOhm resistance, and "<-90dB distortion".
My interest is as follows: I want to have an amplifier with on the one hand an F4 (no gain, no pain) and also an F8 (my version of a SIT follower, no gain, lots of pain). [My F8 is a mash-up of for example ZM's BJT version; I choose the nice 2SJ74 as input, maybe should call it J2/F8 to make things more complex; See attached. 2.]. . . Essential: Same power lines as F4 (25V).
- I envision to be able switch between the two, by swithing the V+ and V1 alternately, and I do not trust a relay DT enough for that. And then also switch the output.
- + Luxury option: on DC, disable the output. . .
but this board is not isolated. GND is common ground. But it probably is bidirectional, having two fets back to back. So that one extra component is needed. An example of a driver that is isolated, is: VOM1271 (Vishay) = Photovoltaic MOSFET Driver With Integrated Fast Turn-Off, for Solid-State Relay. There must be more.
- Any experiences with this use-case?
- Suggestions?
- Experiences?
Attachments
ex Plitron -> Noratel? Zen Pre toroidal
- By dovla83
- Power Supplies
- 3 Replies
Trying to figure out what these guys have to offer but the web site does not say much. Did send an email two days ago to US and Canada divisions asked for a catalogue, so far no dice. Maybe a contact of a sales person?
Looking for the toroidal for the Zen Pre, this one looks really nice. 🙂
Looking for the toroidal for the Zen Pre, this one looks really nice. 🙂
Looking for direction on how to modify a crossover from single to bi-amp input
Hello DiyAudio,
I recently acquired a pair of Duntech Sovereigns (mid-west US) and am trying to figure the feasibility to convert them from single to biamp inputs. Attached are a few pics. While I have done some basic repairs, I have limited experience with crossovers having this many components. Yikes, they are even on drawer slides.
My wife and I collect equipment from the Sov's era, back when I was school-aged, when seems all the cool kids in the magazines had more than one amp. I have some amp pairs that are not easily bridgeable that I'd love to use with the Sovereigns.
Ask any questions. I'll do my best to respond. Thanks in advance for any input.
MnM
I recently acquired a pair of Duntech Sovereigns (mid-west US) and am trying to figure the feasibility to convert them from single to biamp inputs. Attached are a few pics. While I have done some basic repairs, I have limited experience with crossovers having this many components. Yikes, they are even on drawer slides.
My wife and I collect equipment from the Sov's era, back when I was school-aged, when seems all the cool kids in the magazines had more than one amp. I have some amp pairs that are not easily bridgeable that I'd love to use with the Sovereigns.
Ask any questions. I'll do my best to respond. Thanks in advance for any input.
MnM
H2
- By Nelson Pass
- Pass Labs
- 1210 Replies
For the upcoming Burning Amp Festival I created a nice little 2nd Harmonic
Generator. It's similar to what the Korg Nutube does, but uses a Jfet.
I made up a nice batch of them to give away at BAF, and I'm telling you
about it now so you can book your flights, hire babysitters, etc.
You can read all about it at FIRST WATT WATT'S NEW
Generator. It's similar to what the Korg Nutube does, but uses a Jfet.
I made up a nice batch of them to give away at BAF, and I'm telling you
about it now so you can book your flights, hire babysitters, etc.
You can read all about it at FIRST WATT WATT'S NEW
Ultra Amplifier with JFET input and Lateral MOSFET out
- By lineup
- Solid State
- 501 Replies
Bandwidth is 400 kHz
THD at 1 Watt is 0.0004%
The bias is 600mA for good figures.
THD at 1 Watt is 0.0004%
The bias is 600mA for good figures.
AQ1200
- By Don Hathcock
- Car Audio
- 16 Replies
What is the best course of action when everything seems fine but there is no audio output?
All drive signals on the outputs look good.
All power supplies are there.
Relay kicks on and amplifier shows a green light.
The only real strange thing I see is there is "ringing" on the signal at the top of R33 on the output card.
All drive signals on the outputs look good.
All power supplies are there.
Relay kicks on and amplifier shows a green light.
The only real strange thing I see is there is "ringing" on the signal at the top of R33 on the output card.
Audio and Chassis Grounding
- By gerrittube
- Equipment & Tools
- 76 Replies
I use an external soundcard and a pc to measure amplifier circuits. I think I have an issue with audio and chassis grounding.
The amplifier chassis is properly grounded of course. The audio ground and power supply minus are connected to the chassis ground by a 10 Ohm resistor.
A RCA cable or a probe is used to measure the amplifier and is connected to audio ground and audio signal.
The external soundcard is connected to a pc with a standard USB cable. The pc's chassis is also connected to ground.
The issue I'm running into is that the pc's USB connector is internally connected to the pc's chassis (and thereby grounded). So by connecting the USB cable to the pc the 10 Ohm resistor in the amplifier is shorted and there is no longer a separation between the audio ground and the chassis ground. In the amplifier there is a reason for the separation between audio ground and chassis ground. Shorting the 10 Ohm resistor this way seems to affect my measurements.
What can I do to keep the amplifier's grounding intact.
The amplifier chassis is properly grounded of course. The audio ground and power supply minus are connected to the chassis ground by a 10 Ohm resistor.
A RCA cable or a probe is used to measure the amplifier and is connected to audio ground and audio signal.
The external soundcard is connected to a pc with a standard USB cable. The pc's chassis is also connected to ground.
The issue I'm running into is that the pc's USB connector is internally connected to the pc's chassis (and thereby grounded). So by connecting the USB cable to the pc the 10 Ohm resistor in the amplifier is shorted and there is no longer a separation between the audio ground and the chassis ground. In the amplifier there is a reason for the separation between audio ground and chassis ground. Shorting the 10 Ohm resistor this way seems to affect my measurements.
What can I do to keep the amplifier's grounding intact.
Can anyone identify this DC motor from TTWeights Gem V2 TT?
Hi I'm wondering if anyone can identify this brushless DC motor from a TTW Gem V2 turntable? Possibly a Hurst or Maxon but there's no markings of any kind on it.
Alpair 12p + MAOP 7 Gen 2 ideas
- By tomunder
- Full Range
- 2 Replies
I recently acquired a pair of Alpair 12p's which I had planned to build into Scott's Juliet Double Chamber Reflex design
I have since come by a pair of MAOP 7.2's which I'm currently running in a pair of Woden baby labs Storm Shadow V2
I'm now wondering about combining the 2 into one WAW design and I'm after any advice/ideas for doing so
This could be a one box solution like Scott/Dave's design for for A12pw and A5.2/3. (Don't know if this could be adjusted to suit?)
Or my current idea is to continue with the Juliet build and add a separate sealed box on top for the MAOP - something like the image below - top box would obviously need to be the correct size to suit the MAOP (Which I'd also need some help with along with which type of alignment would be best)
Then there's filtering. Run the 12p open and high pass the MAOP? or cross the two over at a certain frequency like a traditional 2-way
or does the sensitivity difference between these two drivers make this whole idea a non-starter? 91.7db for the 12p, 85.8db for the MAOP 7
Any help / ideas greatly appreciated
I have since come by a pair of MAOP 7.2's which I'm currently running in a pair of Woden baby labs Storm Shadow V2
I'm now wondering about combining the 2 into one WAW design and I'm after any advice/ideas for doing so
This could be a one box solution like Scott/Dave's design for for A12pw and A5.2/3. (Don't know if this could be adjusted to suit?)
Or my current idea is to continue with the Juliet build and add a separate sealed box on top for the MAOP - something like the image below - top box would obviously need to be the correct size to suit the MAOP (Which I'd also need some help with along with which type of alignment would be best)
Then there's filtering. Run the 12p open and high pass the MAOP? or cross the two over at a certain frequency like a traditional 2-way
or does the sensitivity difference between these two drivers make this whole idea a non-starter? 91.7db for the 12p, 85.8db for the MAOP 7
Any help / ideas greatly appreciated
"Hancocks", another VersaBox build with Dayton SIG180-4 and AMTHR-4...
- By wolf_teeth
- Multi-Way
- 19 Replies
Attachments
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Hancocks_Right-Final_HD_5-20-25.png -
Hancocks_Right-Final_LevelAdj_0-45_5-20-25.png -
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Hancocks_Schematic_Final1_Voiced.png -
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OTL Tube headphone amp design with 12AU7 and KT66 tubes
- Tubes / Valves
- 108 Replies
Hi all. I've been working on a design for an OTL tube headphone amp. As my starting point, I used the design created by @indaco and @artosalo that can be found here: https://www.diyaudio.com/community/threads/the-6n13s-artosalo-otl-headphone-amplifier.321470/
I have some nice 12au7 and KT66 tubes on hand and I like the sound of them, so I thought I'd try adjusting the design to use those tubes and modeling it in LTSpice (also as an exercise in LTSpice.
I made the following changes to the design:
I set the sine wave input an amplitude of 2.82 to represent the common 2Vrms output from a DAC and put a potentiometer there with the wiper at 0.75.
The result is here:
The result is significantly more power at a lower distortion than my model of the Bottlehead Crack. Turned all the way up, this does 360mW into 300 ohms.
I've heard some people say the 6SN7 is better than the 12au7, so I made a model with those as well and readjusted the resistor values. This version has more gain with concurrent slightly higher distortion than the 12au7 version I came up with:
I do have nice 12au7s on hand, but if I'm going to go to the trouble of building an amp, maybe I want the better tube? This version will do 500mw into 300 ohms
Output impedance is about 85 ohms, which is fine for the high impedance dynamic headphones I intend to use this with, and again much better than the Crack. (Please no suggestions on how to lower the output impedance, this isn't my goal.)
I've included both simulations here for anyone who wants to play with them.
Questions:
Any other comments and suggestions appreciated!
There's a lot of other things I need to figure out before I could actually build this, in particular the power supply and heater wiring and voltages. The original Indaco/Artosalo design used an SMPS for the power heater; I'd like to avoid that, but I need to research transformers and such. I also need to figure out the general wiring and assembly--how I'd actually put this together assuming I'd use point-to-point wiring (which I've never done!). But right now I'm just focused on perfecting the gain stage. I love OTL headphone amps and this has the potential to be a dream piece of gear for me.
Edit: made a mistake on the potentiometer setting which I have corrected
I have some nice 12au7 and KT66 tubes on hand and I like the sound of them, so I thought I'd try adjusting the design to use those tubes and modeling it in LTSpice (also as an exercise in LTSpice.
I made the following changes to the design:
- Changed tubes to 12au7 and KT66
- Ran the control grid of the KT66 back to the B+/Anode line with a small resistance as is commonly done
- Raised the B+ voltage to 300V
- Adjusted the resistor values for the new tubes, with an aim towards minimizing distortion
- Removed the input capacitor—since both tubes are cathode biased, it should be unnecessary. Replaced with a grid-stopper resistor
- Added a potentiometer
I set the sine wave input an amplitude of 2.82 to represent the common 2Vrms output from a DAC and put a potentiometer there with the wiper at 0.75.
The result is here:
The result is significantly more power at a lower distortion than my model of the Bottlehead Crack. Turned all the way up, this does 360mW into 300 ohms.
I've heard some people say the 6SN7 is better than the 12au7, so I made a model with those as well and readjusted the resistor values. This version has more gain with concurrent slightly higher distortion than the 12au7 version I came up with:
I do have nice 12au7s on hand, but if I'm going to go to the trouble of building an amp, maybe I want the better tube? This version will do 500mw into 300 ohms
Output impedance is about 85 ohms, which is fine for the high impedance dynamic headphones I intend to use this with, and again much better than the Crack. (Please no suggestions on how to lower the output impedance, this isn't my goal.)
I've included both simulations here for anyone who wants to play with them.
Questions:
- 12au7 vs 6SN7 in this amp?
- Any suggestions for modifications? Tweaks? I'm particularly interested in lowering that 3rd order harmonic distortion a little (though I'm not sure how audible it actually is? Maybe not at all?) (without removing the KT66 from the design--yes, I know beam tetrodes are more likely to produce 3rd order harmonic distortion, the idea here is to use the KT66)
- I think about how the Feliks amplifiers use two dual triodes in the input stage. I'm not sure how they have them configured--there's a million ways to do it--but I'm wondering if adding a second input triode somewhere would improve the design
Any other comments and suggestions appreciated!
There's a lot of other things I need to figure out before I could actually build this, in particular the power supply and heater wiring and voltages. The original Indaco/Artosalo design used an SMPS for the power heater; I'd like to avoid that, but I need to research transformers and such. I also need to figure out the general wiring and assembly--how I'd actually put this together assuming I'd use point-to-point wiring (which I've never done!). But right now I'm just focused on perfecting the gain stage. I love OTL headphone amps and this has the potential to be a dream piece of gear for me.
Edit: made a mistake on the potentiometer setting which I have corrected
RailMax - Power Amplifier with Rail to Rail output
- By lineup
- Solid State
- 12 Replies
I wanted to create a "Rail to Rail" power amplifier.
This is what I came up with.
I use dual parallel output transistors.
Supply is +/-33V.
Output at 8 Ohm is +/-32.5V = 66W.
Output at 4 Ohm is +/-32.1V = 128W
This is what I came up with.
I use dual parallel output transistors.
Supply is +/-33V.
Output at 8 Ohm is +/-32.5V = 66W.
Output at 4 Ohm is +/-32.1V = 128W
PeeCeeBee V4H GB
- By shaan
- Group Buys
- 1825 Replies
Update (December 17 2022): The very last batch V4H Rev2 boards is going out! More details >Here.<
Update (August 2 2020):
PeeCeeBee V4H has been upgraded to Revision 2. This revision adds MOSFET short circuit protection, VAS buffer SOA protection and a couple minor changes. Full details >Here<. Updated schematic and layout snapshots have been shared below. Updated BOM and Setup Guide links have also been shared at the end of this post. Drill template remains unchanged.
Update (October 6 2021):
V4H Revision 2 PCBs available. Shipping resumed to most countries worldwide.
____________________________________
(Original text from here)
Hello everyone.
The PeeCeeBee V4H is finally here. As promised, PCBs will be available through group buys arranged in this thread.
Since the introduction of PeeCeeBee V4 early last year I have been receiving emails/PMs on a continuous basis with requests for a higher power version of the same amplifier. While most of the default components allowed for the use of a higher voltage PSU and more power would be readily available by paralleling the MOSFETs, it appeared to me that the amplifier's sonics can still be improved without using additional active devices in the signal chain or biasing the MOSFETs to 1A or 2A and turning the setup into a miniature furnace that would dramatically increase its requirements in every accompanying segment from Transformer rating to heatsink size. This is to say that much of V4's unused potential has been attempted to put to use. As a result, we now have PeeCeeBee V4H, the high power PeeCeeBee that won't need to be a furnace to deliver pleasant music. (However, the option for manual bias trimming remains available, very handy in the chilly winter nights IMO!)
A bit of detail: (it doesn't go too deep. 🙂)
The original PeeCeeBee V4 upto Rev1, uses emitter follower VAS and simple miller compensation at VAS stage that gives us a stable Class-AB "current feedback" amplifier with more than enough speed and much lower THD than any of its previous versions. Many members bought the PCBs, assembled them, listened to the amplifier and sent me more encouraging emails than I could imagine. While most of the comments I received on V4's sonics were positive, a few members who bought the PCBs in the group buys reported excellent sonics but only at 500mA or higher MOSFET bias.
V4's distortion at low frequency is very low and its LF performance with music input directly reflects that, with THD level being very low up-to around 2KHz with 100mA MOSFET bias. At gradually higher frequencies THD tended to gradually rise, as it normally would. However, while 500Hz to 5KHz THD measured low, level of higher-order harmonic content at 100mA bias wasn't as low as measured with 500mA/1A bias, resulting in a "thin" sound at low bias. It is a well known fact that higher order harmonics can be annoying at a lower magnitude than lower order harmonics. The output stage crossover distortion with its spiky and subtle nature was naturally the primary suspect and I was absolutely against building an amplifier with 1000V/uS slew rate (so to speak). Experiments followed.
Meanwhile, I stumbled upon online and printed resources that illustrate "tricks" which, when properly applied, make use of the available negative feedback in a standard closed loop amplifier much more efficiently and effectively. After switching between a few of those "tricks" and measuring/listening to the setup for a few weeks I decided on one arrangement that is simple, has a visible improvement in the THD plot, most stable, sounded best, and noticeably better at HF than the vanilla V4 Rev1, at the same 100mA per MOSFET bias. It is a very simple modification of the miller compensation network that corrects HF distortion at output node and further attenuates higher order harmonics by forming a semi-local feedback network between the output and the VAS stage. The original simple miller compensation used just two capacitors. For this mod we need four additional passive components - two resistors and two more capacitors - R31, R32, C7, C8 as seen in the layout and schematic below. The idea is courtesy of the late Peter Baxandall, kindly made available for everyone by Douglas Self in his website. It is a very flexible technique and after much experimentation a combination of the involved components struck my setup, that had the best effect on sonics of this amplifier, and I went along.
The technique is called "Output Inclusive Compensation", some call it "Transitional Miller Compensation". Whatever we call it, the mod is very simple and cheap, but its effect on sound is grand. The most elegant nature of this technique is that it helps the amplifier exactly where it is needed most. It has little effect on total distortion amount for frequencies below 5KHz but works on the crossover spikes and reduces higher order harmonic considerably, leaving THD to be consisting of almost entirely of second and third harmonic which are way less disturbing than say 5th and 7th and are already very low. At HF it works equally effectively reducing higher order harmonics even better and also having more effect on lowering second and third harmonics - for example check the increase in second+third harmonic levels in the 1KHz 10W and 1KHz 100W spectrum shots below. Compare that to the same in the 10KHz 10W and 10KHz 100W spectrum shots.
All in all, PeeCeeBee has yet again been improved in a key segment of its performance, harmonic distribution. The V4H is just as stable as the V4 and it provides not only more power headroom but has much less crossover distortion and sonics that are perceptibly more balanced throughout the octaves. The modification in compensation has also been incorporated in the lower power V4 Rev2 amplifier and it shows the same improvements in both measurement and sonics.
As shown, each of the feedback resistors have been divided into two 4K7 resistors to result into about the same total resistance in parallel but double the total dissipation limit. This will prevent these resistors from overheating during high power output. The 0.1R resistors allow for using unmatched MOSFETs. If your MOSFETs are matched, replace these resistors with wire links (use thick wire).
The PeeCeeBee V4H Revision 2 layout looks like this:
Revision 2 Schematic: (>full size<)
THD Plots: (1KHz - 0.001% source THD, 10KHz - 0.002% source THD, 100mA per MOSFET, 10mA VAS bias, no matching for any transistor pair except Q1 and Q2.)
1KHz 1W into 5R
1KHz 10W into 5R
1KHz 100W into 5R
10KHz 1W into 5R
10KHz 10W into 5R
10KHz 100W into 5R
Specs:
Power - 150W/250W into 8R/4R load with +/-56V PSU (0.1% THD)
Frequency response(simulated) - ~2Hz to ~800KHz (-3dB)
Slew Rate - 100V/uS
Offset variation - +/-10mV
SNR - >110dB
AC gain - 24.5 (28dB)
DC gain - Unity
Input level for 250W into 4R - 1.5VRMS (~4V P-P)
THD:
100Hz 10W - 0.0005%, 100Hz 100W - 0.001%
1KHz 10W - 0.002%, 1KHz 100W - 0.003%
10KHz 10W - 0.002%, 10KHz 100W - 0.005%
Revision 2 BOM >Here<
Revision 2 Setup Guide >Here<
Drill Template >Here<
---------------------------------------------
Group Buy Information:
The layout is 150mm x 61mm Dual Layer.
Batch of 50, 75 or 100 PCBs will be printed depending on interest. The boards will be 2.4mm thick with FR4 material, 60micron copper, HASL finish, white silkscreen and black solder mask.
2. Registered Post (cheaper, 30-40 days delivery time. Available for all countries)
---------------------------------------------
Thanks.
shaan
Update (August 2 2020):
PeeCeeBee V4H has been upgraded to Revision 2. This revision adds MOSFET short circuit protection, VAS buffer SOA protection and a couple minor changes. Full details >Here<. Updated schematic and layout snapshots have been shared below. Updated BOM and Setup Guide links have also been shared at the end of this post. Drill template remains unchanged.
Update (October 6 2021):
V4H Revision 2 PCBs available. Shipping resumed to most countries worldwide.
____________________________________
(Original text from here)
Hello everyone.
The PeeCeeBee V4H is finally here. As promised, PCBs will be available through group buys arranged in this thread.
Since the introduction of PeeCeeBee V4 early last year I have been receiving emails/PMs on a continuous basis with requests for a higher power version of the same amplifier. While most of the default components allowed for the use of a higher voltage PSU and more power would be readily available by paralleling the MOSFETs, it appeared to me that the amplifier's sonics can still be improved without using additional active devices in the signal chain or biasing the MOSFETs to 1A or 2A and turning the setup into a miniature furnace that would dramatically increase its requirements in every accompanying segment from Transformer rating to heatsink size. This is to say that much of V4's unused potential has been attempted to put to use. As a result, we now have PeeCeeBee V4H, the high power PeeCeeBee that won't need to be a furnace to deliver pleasant music. (However, the option for manual bias trimming remains available, very handy in the chilly winter nights IMO!)
A bit of detail: (it doesn't go too deep. 🙂)
The original PeeCeeBee V4 upto Rev1, uses emitter follower VAS and simple miller compensation at VAS stage that gives us a stable Class-AB "current feedback" amplifier with more than enough speed and much lower THD than any of its previous versions. Many members bought the PCBs, assembled them, listened to the amplifier and sent me more encouraging emails than I could imagine. While most of the comments I received on V4's sonics were positive, a few members who bought the PCBs in the group buys reported excellent sonics but only at 500mA or higher MOSFET bias.
V4's distortion at low frequency is very low and its LF performance with music input directly reflects that, with THD level being very low up-to around 2KHz with 100mA MOSFET bias. At gradually higher frequencies THD tended to gradually rise, as it normally would. However, while 500Hz to 5KHz THD measured low, level of higher-order harmonic content at 100mA bias wasn't as low as measured with 500mA/1A bias, resulting in a "thin" sound at low bias. It is a well known fact that higher order harmonics can be annoying at a lower magnitude than lower order harmonics. The output stage crossover distortion with its spiky and subtle nature was naturally the primary suspect and I was absolutely against building an amplifier with 1000V/uS slew rate (so to speak). Experiments followed.
Meanwhile, I stumbled upon online and printed resources that illustrate "tricks" which, when properly applied, make use of the available negative feedback in a standard closed loop amplifier much more efficiently and effectively. After switching between a few of those "tricks" and measuring/listening to the setup for a few weeks I decided on one arrangement that is simple, has a visible improvement in the THD plot, most stable, sounded best, and noticeably better at HF than the vanilla V4 Rev1, at the same 100mA per MOSFET bias. It is a very simple modification of the miller compensation network that corrects HF distortion at output node and further attenuates higher order harmonics by forming a semi-local feedback network between the output and the VAS stage. The original simple miller compensation used just two capacitors. For this mod we need four additional passive components - two resistors and two more capacitors - R31, R32, C7, C8 as seen in the layout and schematic below. The idea is courtesy of the late Peter Baxandall, kindly made available for everyone by Douglas Self in his website. It is a very flexible technique and after much experimentation a combination of the involved components struck my setup, that had the best effect on sonics of this amplifier, and I went along.
The technique is called "Output Inclusive Compensation", some call it "Transitional Miller Compensation". Whatever we call it, the mod is very simple and cheap, but its effect on sound is grand. The most elegant nature of this technique is that it helps the amplifier exactly where it is needed most. It has little effect on total distortion amount for frequencies below 5KHz but works on the crossover spikes and reduces higher order harmonic considerably, leaving THD to be consisting of almost entirely of second and third harmonic which are way less disturbing than say 5th and 7th and are already very low. At HF it works equally effectively reducing higher order harmonics even better and also having more effect on lowering second and third harmonics - for example check the increase in second+third harmonic levels in the 1KHz 10W and 1KHz 100W spectrum shots below. Compare that to the same in the 10KHz 10W and 10KHz 100W spectrum shots.
All in all, PeeCeeBee has yet again been improved in a key segment of its performance, harmonic distribution. The V4H is just as stable as the V4 and it provides not only more power headroom but has much less crossover distortion and sonics that are perceptibly more balanced throughout the octaves. The modification in compensation has also been incorporated in the lower power V4 Rev2 amplifier and it shows the same improvements in both measurement and sonics.
As shown, each of the feedback resistors have been divided into two 4K7 resistors to result into about the same total resistance in parallel but double the total dissipation limit. This will prevent these resistors from overheating during high power output. The 0.1R resistors allow for using unmatched MOSFETs. If your MOSFETs are matched, replace these resistors with wire links (use thick wire).
The PeeCeeBee V4H Revision 2 layout looks like this:
Revision 2 Schematic: (>full size<)
THD Plots: (1KHz - 0.001% source THD, 10KHz - 0.002% source THD, 100mA per MOSFET, 10mA VAS bias, no matching for any transistor pair except Q1 and Q2.)
1KHz 1W into 5R
1KHz 10W into 5R
1KHz 100W into 5R
10KHz 1W into 5R
10KHz 10W into 5R
10KHz 100W into 5R
Specs:
Power - 150W/250W into 8R/4R load with +/-56V PSU (0.1% THD)
Frequency response(simulated) - ~2Hz to ~800KHz (-3dB)
Slew Rate - 100V/uS
Offset variation - +/-10mV
SNR - >110dB
AC gain - 24.5 (28dB)
DC gain - Unity
Input level for 250W into 4R - 1.5VRMS (~4V P-P)
THD:
100Hz 10W - 0.0005%, 100Hz 100W - 0.001%
1KHz 10W - 0.002%, 1KHz 100W - 0.003%
10KHz 10W - 0.002%, 10KHz 100W - 0.005%
Revision 2 BOM >Here<
Revision 2 Setup Guide >Here<
Drill Template >Here<
---------------------------------------------
Group Buy Information:
The layout is 150mm x 61mm Dual Layer.
Batch of 50, 75 or 100 PCBs will be printed depending on interest. The boards will be 2.4mm thick with FR4 material, 60micron copper, HASL finish, white silkscreen and black solder mask.
1. International Air Parcel (recommended, 15-20 days delivery time, but a bit expensive. Covers most countries).
2. Registered Post (cheaper, 30-40 days delivery time. Available for all countries)
---------------------------------------------
Thanks.
shaan
Phoenix Gold M50 | DC Voltage - Popping Crackling Noise
- By mithatcann
- Car Audio
- 8 Replies
Morning all,
I have Phoenix Gold M44 and M50 amps.
I am using M50 amp for midwoofer.
I know, PG typically does not release documents.
For M50 , Even no music is playing, I can hear a crackling sound from speakers if they are connected to the speaker terminal. It still does it with the RCA’s unplugged so Speakers connected but no rca signal. We measure each channel (L and R) voltage. DC voltage is not under 50mV. I think 50mV is still considered acceptable. Problem is continue for both channels. We hear turn on and or turn off pops too. The m50 is a powerful and beautiful sounding amp if it’s working properly. Would you support us on this matter?
I need olsa Gain Pot. Nobody makes that 50K c taper pot anymore. I try to rebuilt them and clean them.
It would be great if there was a schematic diagram. Does anyone have such a file on this subject?
I have Phoenix Gold M44 and M50 amps.
I am using M50 amp for midwoofer.
I know, PG typically does not release documents.
For M50 , Even no music is playing, I can hear a crackling sound from speakers if they are connected to the speaker terminal. It still does it with the RCA’s unplugged so Speakers connected but no rca signal. We measure each channel (L and R) voltage. DC voltage is not under 50mV. I think 50mV is still considered acceptable. Problem is continue for both channels. We hear turn on and or turn off pops too. The m50 is a powerful and beautiful sounding amp if it’s working properly. Would you support us on this matter?
I need olsa Gain Pot. Nobody makes that 50K c taper pot anymore. I try to rebuilt them and clean them.
It would be great if there was a schematic diagram. Does anyone have such a file on this subject?
Folsom EC7293: PVI Powered Frontend, 60/120w 8/4ohm
- By Destroyer OS
- Group Buys
- 484 Replies
Folsom EC7293: PVI Powered Frontend Amplifier, 60/120w 8/4ohm, 0.0005% THD
**Updated: Lower distortion with a slightly different board.
**Updated 2: Distortion is even lower than before, found a piece of steel was interfering with previous measurements. (thought it was tinned copper)
Alright everyone! We’ve got the redesign done.
(Image of prototype)
The EC7293 uses 2 chip amps in parallel for high power with a discrete error correction frontend which reduces distortion; and has very low memory distortion. High sensitivity makes it perfect for a variety of sources with 8ohm and 4ohm speakers.
Input impedance: 27k
Gain: 32db
Distortion 1K; 8ohm; full power w/Antek AS-3225: <0.0005% (immeasurable by us)
No Load
8ohm
4ohm
2ohm
Loopback
Board size: 6.25x2.25"
*****There is not a mirrored left/right set because it would screw up the feedback layout*****
Discrete front end: 4 transistors
PVI: The frontend uses a photovoltaic power supply for galvanic isolation of the signal path. It uses a G4 LED bulb with a current source to disable the onboard driver of the G4.
Distortion: <0.0005%
High power: These are running in "modular" mode so that they can handle a 4 ohm load with some dips, while providing substantial power with a max output current of 20A. The Antek AS-3225 is a great fit for 60/120w. More power may be possible if you follow the guidelines of the TDA7293 datasheet and make provisions with higher voltage capacitors, and larger heatsinks.
Terminals: Happy to say we've found some that are based on a copper metallurgy, that accept decent sized wire, and don't strip too easily (I can torque them pretty good with screwdriver) that the boards are made to fit, and I recommend in the BOM.
Input Capacitor: This one is less sensitive to capacitors compared to the DIY7297. It has provisions for the same PHE426 and other caps. There is a slot-hole next to the pads so you can zip tie on larger caps and it has extra pads on the bottom to connect off board/long input capacitors.
CFC, smart PCB layout, & Copper Pours: Trace routing is optimized to improve performance and the power capacitors are placed for field cancellation (CFC); and copper pours are used for lower inductance.
Dualpole PSU PCB
Board Size: 4.25x3"
TO220 Diodes
CFC, smart PCB layout, & Copper Pours
Via holes for snap caps
RC and bypass: dampen the transformer & reduce noise
Suggested implementation with EC7293:
**2U may work in dual mono with two smaller (shorter) transformers
Price & Amount needed to Print:
In order to print these up so I don't run out the day after, I need a commitment of 12x, two EC7293 boards and one PSU board. I'm hoping to see a lot more than 12x. To anyone that liked the DIY7297, this one is better, simply better.
EC7293+G4LEDR PCB $45ea (you'll need 2, to make a stereo amp)
DualPole PSU PCB $40ea
Shipping USA $8
Shipping International $16
And it will come with a BOM and some build details.
**Updated: Lower distortion with a slightly different board.
**Updated 2: Distortion is even lower than before, found a piece of steel was interfering with previous measurements. (thought it was tinned copper)
Alright everyone! We’ve got the redesign done.
(Image of prototype)
The EC7293 uses 2 chip amps in parallel for high power with a discrete error correction frontend which reduces distortion; and has very low memory distortion. High sensitivity makes it perfect for a variety of sources with 8ohm and 4ohm speakers.
Input impedance: 27k
Gain: 32db
Distortion 1K; 8ohm; full power w/Antek AS-3225: <0.0005% (immeasurable by us)
No Load
8ohm
4ohm
2ohm
Loopback
Board size: 6.25x2.25"
*****There is not a mirrored left/right set because it would screw up the feedback layout*****
Discrete front end: 4 transistors
PVI: The frontend uses a photovoltaic power supply for galvanic isolation of the signal path. It uses a G4 LED bulb with a current source to disable the onboard driver of the G4.
Distortion: <0.0005%
High power: These are running in "modular" mode so that they can handle a 4 ohm load with some dips, while providing substantial power with a max output current of 20A. The Antek AS-3225 is a great fit for 60/120w. More power may be possible if you follow the guidelines of the TDA7293 datasheet and make provisions with higher voltage capacitors, and larger heatsinks.
Terminals: Happy to say we've found some that are based on a copper metallurgy, that accept decent sized wire, and don't strip too easily (I can torque them pretty good with screwdriver) that the boards are made to fit, and I recommend in the BOM.
Input Capacitor: This one is less sensitive to capacitors compared to the DIY7297. It has provisions for the same PHE426 and other caps. There is a slot-hole next to the pads so you can zip tie on larger caps and it has extra pads on the bottom to connect off board/long input capacitors.
CFC, smart PCB layout, & Copper Pours: Trace routing is optimized to improve performance and the power capacitors are placed for field cancellation (CFC); and copper pours are used for lower inductance.
Dualpole PSU PCB
Board Size: 4.25x3"
TO220 Diodes
CFC, smart PCB layout, & Copper Pours
Via holes for snap caps
RC and bypass: dampen the transformer & reduce noise
Suggested implementation with EC7293:
- 18000uF to 24000uF per rail
- Antek AS-3225 transformer
- Keratherm insulators from DIYAudio store. (Chip tabs are 1.1” apart).
- Heatsinks need to be larger than used on the 7297, nearly any enclosure with heatsinks for sides should work
- 3U enclosure from DIYAudio store is a good fit. **
- 2x Duapole's for dual mono with 2x transformers (Antek AS-2225)
**2U may work in dual mono with two smaller (shorter) transformers
Price & Amount needed to Print:
In order to print these up so I don't run out the day after, I need a commitment of 12x, two EC7293 boards and one PSU board. I'm hoping to see a lot more than 12x. To anyone that liked the DIY7297, this one is better, simply better.
EC7293+G4LEDR PCB $45ea (you'll need 2, to make a stereo amp)
DualPole PSU PCB $40ea
Shipping USA $8
Shipping International $16
And it will come with a BOM and some build details.
Anybody else use flower pots for midrange sub-enclosures?
- Multi-Way
- 26 Replies
At the InDIYana event thanks to @wolf_teeth I picked up some Dayton RS125-4s (5” mid, which is what the flower pots are for) and SB Acoustics SB19ST-C000-4 tweeter, which I’m matching to a 3D printed waveguide. I decided to make a 3-way using a Dayton knock-down enclosure.
Woofer is a GRS 8SW-4HE which is a very well built long excursion subwoofer.
Class AB amp clipping at 55v under no load, help
- Solid State
- 62 Replies
Hey everyone,
I’ve built a 1000W RMS amplifier designed to drive a 2Ω load. I'm supplying it with ±80V rails. However, when I check the output voltage (without any load connected), the signal starts clipping at only 55V peak.
I was expecting a higher swing, given the rail voltage. Could this be due to a weak driver ? Would adding a predriver help improve the voltage swing?
Any insights or suggestions would be appreciated
I’ve built a 1000W RMS amplifier designed to drive a 2Ω load. I'm supplying it with ±80V rails. However, when I check the output voltage (without any load connected), the signal starts clipping at only 55V peak.
I was expecting a higher swing, given the rail voltage. Could this be due to a weak driver ? Would adding a predriver help improve the voltage swing?
Any insights or suggestions would be appreciated