Would This Shape Work?
- By asid99
- Subwoofers
- 23 Replies
TLDR= Hello Everyone. I know this is too much information just for an enclosure question, but I feel it was necessary in order to explain the design choice. My actual question is at the end. Regarding turbulence/resonance/avoiding absolute garbage sound.
I have a 1999 Chevy k1500 Suburban and would like to make a ported box for where the spare tire goes on the inside. I would like to recess the subwoofer into the box and cover it with a protective cage, as it is an SUV at the end of the day., and don't want a nice hole in my woofer . I am also going to be designing a "raised floor" around the box, for the cargo area with some drawers so I can keep tools and such on hand, but still have usable room in the back. Ideally, I would like to wrap both the box and drawer system with OEM style, matching carpet so they don't look out of place.
I started playing around in CAD and I think I have found a design that might work? I tried to smooth out the pathway and design it to be made with 2 layers of 3/4inch, so 1.5 inch total wall thickness. The subwoofer mounting side endcap, would probably be a little thicker as I would like the subwoofer as recessed as possible.
QUESTION=
I'm not too sure on the porting of the box. I saw some models showing resonance in various shape boxes, and unfortunately was unable to find something that I feel would translate. I have the internal volume calculated according to the sub spec sheet. However, I did not factor in the displacement of the woofer itself but that's minor details. In an attempt to reduce turbulence, the end of the port is slightly flared out, and rounded so there are no edges, on the interior except for the endcaps which would just be sandwiched on. My question is, conceptually, would the shape of the box/port work? I would really appreciate some technical guidance. Thank you
I have a 1999 Chevy k1500 Suburban and would like to make a ported box for where the spare tire goes on the inside. I would like to recess the subwoofer into the box and cover it with a protective cage, as it is an SUV at the end of the day., and don't want a nice hole in my woofer . I am also going to be designing a "raised floor" around the box, for the cargo area with some drawers so I can keep tools and such on hand, but still have usable room in the back. Ideally, I would like to wrap both the box and drawer system with OEM style, matching carpet so they don't look out of place.
I started playing around in CAD and I think I have found a design that might work? I tried to smooth out the pathway and design it to be made with 2 layers of 3/4inch, so 1.5 inch total wall thickness. The subwoofer mounting side endcap, would probably be a little thicker as I would like the subwoofer as recessed as possible.
QUESTION=
I'm not too sure on the porting of the box. I saw some models showing resonance in various shape boxes, and unfortunately was unable to find something that I feel would translate. I have the internal volume calculated according to the sub spec sheet. However, I did not factor in the displacement of the woofer itself but that's minor details. In an attempt to reduce turbulence, the end of the port is slightly flared out, and rounded so there are no edges, on the interior except for the endcaps which would just be sandwiched on. My question is, conceptually, would the shape of the box/port work? I would really appreciate some technical guidance. Thank you
Attachments
Adcom GFA 555 II speaker buzz when RCA's connected
- By DaveFred
- Solid State
- 1 Replies
Problem with my GFA-555II's.
When amp is turned on with speaker connected and nothing else connected to the amplifier, speaker output from amp is pretty quiet.
Connect an RCA cable, either Blue Jeans or Amazon, then connected to a Parasound P6 or Adcom GFP-710 preamp or nothing, speaker has quite a hum. Simply plugging anything into the amplifier input causes the amplifier output to make a buzz/hum in the speaker.
Any ideas?
(yes, I am using two in bridged mode)
Thank you,
David.
When amp is turned on with speaker connected and nothing else connected to the amplifier, speaker output from amp is pretty quiet.
Connect an RCA cable, either Blue Jeans or Amazon, then connected to a Parasound P6 or Adcom GFP-710 preamp or nothing, speaker has quite a hum. Simply plugging anything into the amplifier input causes the amplifier output to make a buzz/hum in the speaker.
Any ideas?
(yes, I am using two in bridged mode)
Thank you,
David.
Krell KAV-250A/3 bias and DC offset
- By bdbell
- Solid State
- 4 Replies
I have just completed a recap on a Krell KAV-250a/3 - one amp board was blown and it wasn't worth repairing so I have recapped just two of the 3 amp boards. I have been searching and can not seem to find anywhere what the bias should be set to, or how to set it...I know I should have found this out before starting but I emailed Krell and posted to another forum and got no replies.
Obviously there are only two adjustments so it won't be too hard to figure out which one does what...but what should the bias be set to - and where to measure it?
Obviously there are only two adjustments so it won't be too hard to figure out which one does what...but what should the bias be set to - and where to measure it?
Technics SE-A1000 Amplifier
- By Revoxis
- Solid State
- 88 Replies
Hello,
Hope someone can help me.
I'm new to this forum so hopefully i'm asking the right question. I have Technics SE-A1000 Amplifier wich blows it fuse right away when connected to the AC power line.
Couple things i've already investigated:
1. If i remove the white ribbon cable to the mainboard and put a new fuse in it, the amplifier turns on and i can turn it on and off by pressing the button. (Leads me to mainboard issue)
2. I checked all 4 Rectifier Diodes. First i measured them in circuit, but read some stuff that it might be interffered by other components. Therefore i took them out and measured them one by one.
This is the result:
From top to the bottom.
1. This one seems fine and when measure positive on negative and negative on positive it gives me 0L (I believe this is correct)
2. This one give's me strange readings on both sides. My conclusion is that this one is defective.
3. This one seems fine as well.
4. And this one seems fine too.
However my main problem now is that i cannot find a replacement for these rectifier diodes, they read P300D GI 9512L
Spec sheet
https://www.vishay.com/docs/88691/p300.pdf
I found another one wich is the following
https://www.vishay.com/docs/88516/1n5400.pdf
Does this mean i can safely replace them with a 1N5402 Diode?
Many thanks!
Greetings!.
Mark
Hope someone can help me.
I'm new to this forum so hopefully i'm asking the right question. I have Technics SE-A1000 Amplifier wich blows it fuse right away when connected to the AC power line.
Couple things i've already investigated:
1. If i remove the white ribbon cable to the mainboard and put a new fuse in it, the amplifier turns on and i can turn it on and off by pressing the button. (Leads me to mainboard issue)
2. I checked all 4 Rectifier Diodes. First i measured them in circuit, but read some stuff that it might be interffered by other components. Therefore i took them out and measured them one by one.
This is the result:
From top to the bottom.
1. This one seems fine and when measure positive on negative and negative on positive it gives me 0L (I believe this is correct)
2. This one give's me strange readings on both sides. My conclusion is that this one is defective.
3. This one seems fine as well.
4. And this one seems fine too.
However my main problem now is that i cannot find a replacement for these rectifier diodes, they read P300D GI 9512L
Spec sheet
https://www.vishay.com/docs/88691/p300.pdf
I found another one wich is the following
https://www.vishay.com/docs/88516/1n5400.pdf
Does this mean i can safely replace them with a 1N5402 Diode?
Many thanks!
Greetings!.
Mark
Help understanding cathode bypass capacitor
- Tubes / Valves
- 44 Replies
I have been studying various amplifier schematics over the past few weeks, and I have been reading a lot of threads, but I can't find a precise answer about what effect a cathode bypass resistor has on the sound quality of a hi-fi audio power amplifier. One old thread turned into a multi-page argument over whether to use one or not. It seems that opinions go both ways on that, and that's not my question. What I want to know, and can't really find answers for are:
1) What effect does using a cathode bypass capacitor have on the sound quality of an amplifier that has a circuit with one, and why?
2) If one is used in a circuit, how should the "ideal" size be calculated? I found this formula in an old closed thread: Choose a value where 1/(2πFC) = .5*R, where R=the cathode resistor value in ohms and F=low frequency cutoff (-3dB). That's fine if the formula is correct, but I have no idea why it should be that size or what effect more or less capacitance would have on sound quality. A quote from an old closed thread, "I remember a now fairly famous tube designer who ... always spec'd a 1000uf cathode bypass cap, people would ask why such a large cap? He would never answer." Add me to the list of those asking the question. Suppose hypothetically that the value is too low? Is bigger better? Is there a point where increasing size does not matter?
3) If it is correctly sized, is changing the type of the capacitor likely to make any difference in sound quality and if so, why? Hypothetically, what if it's the cheapest and worst quality electrolytic swapped out for a high quality electrolytic or some other more expensive type?
Edit: I am referring to push-pull class A amplifiers only, and only those with a single resitor and a single capacitor as in this test circuit from the 1955 article cited in posts below:
1) What effect does using a cathode bypass capacitor have on the sound quality of an amplifier that has a circuit with one, and why?
2) If one is used in a circuit, how should the "ideal" size be calculated? I found this formula in an old closed thread: Choose a value where 1/(2πFC) = .5*R, where R=the cathode resistor value in ohms and F=low frequency cutoff (-3dB). That's fine if the formula is correct, but I have no idea why it should be that size or what effect more or less capacitance would have on sound quality. A quote from an old closed thread, "I remember a now fairly famous tube designer who ... always spec'd a 1000uf cathode bypass cap, people would ask why such a large cap? He would never answer." Add me to the list of those asking the question. Suppose hypothetically that the value is too low? Is bigger better? Is there a point where increasing size does not matter?
3) If it is correctly sized, is changing the type of the capacitor likely to make any difference in sound quality and if so, why? Hypothetically, what if it's the cheapest and worst quality electrolytic swapped out for a high quality electrolytic or some other more expensive type?
Edit: I am referring to push-pull class A amplifiers only, and only those with a single resitor and a single capacitor as in this test circuit from the 1955 article cited in posts below:
3 ways active speakers boombox Bluetooth & Wifi with Arylic Amp 2.1
Hi, sharing here my new pyramid boombox project equipped with:
The project finalized:
Project summary:
The objective was to get strong bass and original design with a pyramid (base:25cm, height:70 cm) AND with a small size.
Getting good bass despite such a small volume (around 5 litters) is clearly a challenge. The small 5 inch Tang Band sub, plus the 2 passive speakers on the sides generate a impressive bass for such a small volume.
The 2 passive speakers represent around twice the sub size and increase the volume of air moved globally.
With passive speakers usage, it is absolutely key to avoid air leak; which is not that easy specifically at the level of the speakers, with cables crossing the box.
At the end, I'm very happy by the resulting sound and the clean bass from the Arylic amp 2.1 even at high volume.
I used the Arylic 2.1 board which is very powerful, flexible (you can configure it with a specific tool), and a sound without distortion even at high level.
The sub channel supports 100W in 2 Ohm, and I used a 4 Ohm speaker, resulting into 50 W. It ensures clean sound with no distortion by the Arylic amplifier, even with a massive excursion of the speaker.
Front side, with the controls integrated into te Arylic board (input leds, standby, Bass, Trebble & volume):
Back side, with the switches to select the equalization preset, Ethernet, power, line input, usb, and ... 3 holes for the air
With the ADC input key of the Arylic board, I have configured 3 different equalisations selected with buttons on the back.
Very helpful capability! as I use the speakers for TV, connecting the Arylic Amp 2.1 board in Bluetooth to an Apple TV, with a equalizer preset for crystal voices, and I also use it to listen music, with another specific equalizer preset.
I regret that there is not yet the possibility to control the preset from the 4Stream app.
The settings for each speaker is easy to adjust from the Arylic workbench:
I used the Arylic ACP Workbench, a powerful tools to configure the DSP, in order to set filters, with the medium on the right channel and tweeter on the left one, with a cut frequency at 3k5.
The result of this setup is obviously mono, but on such boombox, the left and right speakers are so close that you don’t get a good stereo effect anyhow.
Note that with ACP Workbench I have set the sub output as the Left+Right input.
And the active filter is far more flexible than a passive filter for the tuning to the speakers tone.
On top of the workbench, you can also change the Bass & trebbles without moving from your sofa, with the Arylic 4Stream App:
Last, some picture of the build:
The "special" tweeter: a ribbon tweeter, and the passive speakers on the right.
Note that I created an isolated volume for the medium speaker using PVC tube of 10 cm.
The Arylic 2.1 board under the box:
Why a capacity as there is an active filter: the ribbon tweeter doesnt support DC and it is mandatory to protect it with a cap.
Next project with Arylic board? May be a child Pyramid, without sub speaker, to get a full stereo effect, putting it at the other side of the room. The board supports indeed multi-"rooms" capabilities in Wifi
- 1 Arylic Amp 2.1 amplifier (2x50W + 1x100W sub), supporting WiFi, Airplay, Spotify Connect & Bluetooth 5.0
- 1 Sub TANG BAND W5-1138SMF
- 2 passive speakers DAYTON AUDIO DSA115-PR
- 1 medium Monacor MSH-116
- 1 ribbon tweeter FOUNTEK NEO CD 3.5H
The project finalized:
Project summary:
The objective was to get strong bass and original design with a pyramid (base:25cm, height:70 cm) AND with a small size.
Getting good bass despite such a small volume (around 5 litters) is clearly a challenge. The small 5 inch Tang Band sub, plus the 2 passive speakers on the sides generate a impressive bass for such a small volume.
The 2 passive speakers represent around twice the sub size and increase the volume of air moved globally.
With passive speakers usage, it is absolutely key to avoid air leak; which is not that easy specifically at the level of the speakers, with cables crossing the box.
At the end, I'm very happy by the resulting sound and the clean bass from the Arylic amp 2.1 even at high volume.
I used the Arylic 2.1 board which is very powerful, flexible (you can configure it with a specific tool), and a sound without distortion even at high level.
The sub channel supports 100W in 2 Ohm, and I used a 4 Ohm speaker, resulting into 50 W. It ensures clean sound with no distortion by the Arylic amplifier, even with a massive excursion of the speaker.
Front side, with the controls integrated into te Arylic board (input leds, standby, Bass, Trebble & volume):
Back side, with the switches to select the equalization preset, Ethernet, power, line input, usb, and ... 3 holes for the air
With the ADC input key of the Arylic board, I have configured 3 different equalisations selected with buttons on the back.
Very helpful capability! as I use the speakers for TV, connecting the Arylic Amp 2.1 board in Bluetooth to an Apple TV, with a equalizer preset for crystal voices, and I also use it to listen music, with another specific equalizer preset.
I regret that there is not yet the possibility to control the preset from the 4Stream app.
The settings for each speaker is easy to adjust from the Arylic workbench:
I used the Arylic ACP Workbench, a powerful tools to configure the DSP, in order to set filters, with the medium on the right channel and tweeter on the left one, with a cut frequency at 3k5.
The result of this setup is obviously mono, but on such boombox, the left and right speakers are so close that you don’t get a good stereo effect anyhow.
Note that with ACP Workbench I have set the sub output as the Left+Right input.
And the active filter is far more flexible than a passive filter for the tuning to the speakers tone.
On top of the workbench, you can also change the Bass & trebbles without moving from your sofa, with the Arylic 4Stream App:
Last, some picture of the build:
The "special" tweeter: a ribbon tweeter, and the passive speakers on the right.
Note that I created an isolated volume for the medium speaker using PVC tube of 10 cm.
The Arylic 2.1 board under the box:
Why a capacity as there is an active filter: the ribbon tweeter doesnt support DC and it is mandatory to protect it with a cap.
Next project with Arylic board? May be a child Pyramid, without sub speaker, to get a full stereo effect, putting it at the other side of the room. The board supports indeed multi-"rooms" capabilities in Wifi
For Sale MOSFET: Toshiba 2SK1530-Y/2SJ201-Y
All Sold : Matched Toshiba 2SK1530-Y / 2SJ201-Y Mosfets
SOLD (1) matched quad NN-PP consisting of 2 pairs - 4 mosfets all measuring 6.30A at 3Vgs - $55.USD
SOLD (1) matched octet NNNN-PPPP consisting of 4 pairs - 8 mosfets all measuring 6.35A at 3Vgs - $115.USD
These are new genuine Toshiba matched by and purchased from Spencer (Fet Audio) back in 2020
I ordered them early enough to enable choosing N-P matches
Free shipping US 48 states only if Paypal 'friend or relative'
'
SOLD (1) matched quad NN-PP consisting of 2 pairs - 4 mosfets all measuring 6.30A at 3Vgs - $55.USD
SOLD (1) matched octet NNNN-PPPP consisting of 4 pairs - 8 mosfets all measuring 6.35A at 3Vgs - $115.USD
These are new genuine Toshiba matched by and purchased from Spencer (Fet Audio) back in 2020
I ordered them early enough to enable choosing N-P matches
Free shipping US 48 states only if Paypal 'friend or relative'
'
COSSOR WE300B
COSSOR WE 300B (made by LINLAI)
price $545
LINLAI is formed by a team of engineers who left Psvane in 2019.
THE COSSOR WE300B is made by LINLAI for our specification.
COSSOR/ LINLAI's WE-series offering are identical to Psvane WE series. There is NO difference. They are 100%, identical, visually and electronically.
THe COSSOR WE300B is a overhung filament design...
Here is the Stereophile Review of COSSOr/LinLai
https://www.stereophile.com/content/gramophone-dreams-48-venus-tube-western-electrics-300b
price $545
LINLAI is formed by a team of engineers who left Psvane in 2019.
THE COSSOR WE300B is made by LINLAI for our specification.
COSSOR/ LINLAI's WE-series offering are identical to Psvane WE series. There is NO difference. They are 100%, identical, visually and electronically.
THe COSSOR WE300B is a overhung filament design...
https://www.stereophile.com/content/gramophone-dreams-48-venus-tube-western-electrics-300b
Will this replacement subwoofer work?
- By PABLITHO
- Subwoofers
- 37 Replies
I have two subwoofers using B&C 18TBX100 drivers currently installed in my HT system. Recently, it was pointed out to me that the natural response of these drivers looks like this:
Note the falling response below 100Hz. By 20Hz, it is -37dB compared to reference. It was pointed out to me that I might get better performance if I changed the driver to something which was more linear across the frequency range which I am using, which is 15Hz - 100Hz. I ideally want something with excellent low bass performance, particularly between 15-30Hz.
Since my subwoofer boxes have already been constructed, I am seeking opinions as to whether this replacement subwoofer driver will be a good fit. Any replacement driver MUST fit in these boxes.
The existing box is 60cm x 60cm x 60cm, with an internal volume of 165L. It is sealed.
This is a link to the specifications of my current driver, the B&C 18TBX100: https://www.bcspeakers.com/en/products/lf-driver/18-0/8/18tbx100
Note that the Vas is 212L, Qts 0.35
The replacement driver I am thinking of is this, the Faital 18HP1030: https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=20107013518
The Vas is 185L, Qts 0.41
The replacement driver has a much more attractive frequency response curve:
It is -12dB at 20Hz (compared to -37dB for my current driver).
There are a number of other drivers from the same manufacturer I could consider, such as these:
https://faitalpro.com/it/products/LF_Loudspeakers/product_details/index.php?id=201070135
https://faitalpro.com/it/products/LF_Loudspeakers/product_details/index.php?id=201070125
https://faitalpro.com/it/products/LF_Loudspeakers/product_details/index.php?id=201070138
https://faitalpro.com/it/products/LF_Loudspeakers/product_details/index.php?id=201070155
I tried modelling the predicted behaviour of the driver using VituixCAD but I failed because this is my first time using this software.
I would like to know whether you think that I would gain an improvement if I replace my current driver with this one. I think the answer is yes for a few reasons:
Thank you in anticipation of your responses.
Paolo
Note the falling response below 100Hz. By 20Hz, it is -37dB compared to reference. It was pointed out to me that I might get better performance if I changed the driver to something which was more linear across the frequency range which I am using, which is 15Hz - 100Hz. I ideally want something with excellent low bass performance, particularly between 15-30Hz.
Since my subwoofer boxes have already been constructed, I am seeking opinions as to whether this replacement subwoofer driver will be a good fit. Any replacement driver MUST fit in these boxes.
The existing box is 60cm x 60cm x 60cm, with an internal volume of 165L. It is sealed.
This is a link to the specifications of my current driver, the B&C 18TBX100: https://www.bcspeakers.com/en/products/lf-driver/18-0/8/18tbx100
Note that the Vas is 212L, Qts 0.35
The replacement driver I am thinking of is this, the Faital 18HP1030: https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=20107013518
The Vas is 185L, Qts 0.41
The replacement driver has a much more attractive frequency response curve:
It is -12dB at 20Hz (compared to -37dB for my current driver).
There are a number of other drivers from the same manufacturer I could consider, such as these:
https://faitalpro.com/it/products/LF_Loudspeakers/product_details/index.php?id=201070135
https://faitalpro.com/it/products/LF_Loudspeakers/product_details/index.php?id=201070125
https://faitalpro.com/it/products/LF_Loudspeakers/product_details/index.php?id=201070138
https://faitalpro.com/it/products/LF_Loudspeakers/product_details/index.php?id=201070155
I tried modelling the predicted behaviour of the driver using VituixCAD but I failed because this is my first time using this software.
I would like to know whether you think that I would gain an improvement if I replace my current driver with this one. I think the answer is yes for a few reasons:
- the natural frequency response curve looks better
- the Vas of 185L is closer to my enclosure volume of 165L, as opposed to my current driver which has a Vas of 212L
- the Qts of the new speaker is 0.41, compared to the Qts of the old speaker of 0.35. If I understand correctly, the smaller the enclosure volume compared to the Vas, the stiffer the air spring, which therefore lowers the Qts even more. What are the effects of this? Will it make the driver more efficient?
Thank you in anticipation of your responses.
Paolo
USB Sniffer (protocol analyzer) using Wireshark
- By tubekiddo
- Equipment & Tools
- 6 Replies
Hi,
While troubleshooting a USB device I came across a low cost USB Sniffer (protocol analyser) which uses Wireshark Capture program.
I want to share with the community.
I myself built two units which work like a charm. The soldering is a bit challenging because of high density SMD part population on the PCB but it is possible to hand solder everything. I ordered the PCB from JLCPCB and parts from mouser and LCSC (China). All parts are readily available and all software/firmware is available free of charge (incl. sources!).
I want to thank again Alex who made this available for free. Professional USB protocol analyzer are costing thousands of $.
Links:
GitHub project: https://github.com/ataradov/usb-sniffer
A video of building a unit, very helpful: https://www.downtowndougbrown.com/2023/08/building-alex-taradovs-open-source-usb-sniffer/
Hackaday article: https://hackaday.com/2023/06/13/cheap-usb-sniffer-has-wireshark-interface/
Hardware obsolete: https://github.com/ataradov/usb-sniffer/issues/7
Also read the discussions in GitHub since it contains some value information about obsolete parts and building the software from the sources (incl. executable for MacOS)
While troubleshooting a USB device I came across a low cost USB Sniffer (protocol analyser) which uses Wireshark Capture program.
I want to share with the community.
I myself built two units which work like a charm. The soldering is a bit challenging because of high density SMD part population on the PCB but it is possible to hand solder everything. I ordered the PCB from JLCPCB and parts from mouser and LCSC (China). All parts are readily available and all software/firmware is available free of charge (incl. sources!).
I want to thank again Alex who made this available for free. Professional USB protocol analyzer are costing thousands of $.
Links:
GitHub project: https://github.com/ataradov/usb-sniffer
A video of building a unit, very helpful: https://www.downtowndougbrown.com/2023/08/building-alex-taradovs-open-source-usb-sniffer/
Hackaday article: https://hackaday.com/2023/06/13/cheap-usb-sniffer-has-wireshark-interface/
Hardware obsolete: https://github.com/ataradov/usb-sniffer/issues/7
Also read the discussions in GitHub since it contains some value information about obsolete parts and building the software from the sources (incl. executable for MacOS)
Dakar Rally
- By UniQ
- The Lounge
- 15 Replies
Beginning of a new year and it's again time for the famous, or rather infamous due to the death/injury tolls, Dakar Rally (formerly aka Paris-Dakar Rally), not a huge motor sport fan but this legendary rally have always fascinated me, maybe due to in my younger past when I did a bit motocross riding in the woods or a sand mining pit mostly on a 250cc (for a short period did also have a very old Yamaha 465cc from early 80's which was brutal to kick-start, will never forget all those bruises on my right foot-sole lol ), and back then had my young utopian daydreams of maybe one day participating in it, no I don't think I would have been anywhere near a winner but just for the heck of it and having done it ones, well it stayed a dream.
Finland did also have a golden age period in the car section where they won every year between the 1987 to 1991, most of them by Ari Vatanen except for 1988 which was won by Juha Kankkunen, both known former rally drivers, and having a glass of milk at goal to celebrate the win was the norm, of course.
Ari on the left, and Juha:
https://www.iltalehti.fi/ralli/a/67649176-fd83-42e4-86d2-aceffe7198e6
https://web.archive.org/web/2023011.../ralli/a/67649176-fd83-42e4-86d2-aceffe7198e6
Anyhow, for 2024 Dakar Rally, the 46th edition which have just kicked off, is now hosted by Saudi Arabia and is going on between 5 to 19 January.
Living in these days and age of internet it's thankfully easy to get a glimpse of each days stages on their YouTube channel, any other Dakar rally fans and followers around here?
https://www.youtube.com/@OfficialDakar
https://en.wikipedia.org/wiki/Dakar_Rally
https://www.dakar.com/en/
https://www.redbull.com/int-en/dakar-rally-need-to-know (good reading)
https://web.archive.org/web/20240107084022/https://www.redbull.com/int-en/dakar-rally-need-to-know
Finland did also have a golden age period in the car section where they won every year between the 1987 to 1991, most of them by Ari Vatanen except for 1988 which was won by Juha Kankkunen, both known former rally drivers, and having a glass of milk at goal to celebrate the win was the norm, of course.
Ari on the left, and Juha:
https://www.iltalehti.fi/ralli/a/67649176-fd83-42e4-86d2-aceffe7198e6
https://web.archive.org/web/2023011.../ralli/a/67649176-fd83-42e4-86d2-aceffe7198e6
Anyhow, for 2024 Dakar Rally, the 46th edition which have just kicked off, is now hosted by Saudi Arabia and is going on between 5 to 19 January.
Living in these days and age of internet it's thankfully easy to get a glimpse of each days stages on their YouTube channel, any other Dakar rally fans and followers around here?
https://www.youtube.com/@OfficialDakar
https://en.wikipedia.org/wiki/Dakar_Rally
https://www.dakar.com/en/
https://www.redbull.com/int-en/dakar-rally-need-to-know (good reading)
https://web.archive.org/web/20240107084022/https://www.redbull.com/int-en/dakar-rally-need-to-know
Replacing Bias Pots in Forte Amplifiers
- By Nexus9
- Solid State
- 3 Replies
Fellow Earthlings;
I've run across some casual discussion here on the forum regarding the bias pots in the Forte amps, but never any hard core information about how to do it. So (having done it) I thought I might be able to contribute by passing on what I've learned. Please remember, this is just one way to go about this - if you have found a different way, please add it below, you'll be helping everyone who reads this thread!
The work I did was on a model 5 and 6. The model 4 has identical circuit boards, so we know this is good information for the 4, 5, and 6. The 1 and 3 were different animals, and the 7 I'm not familiar with, so please accept this info as valid if you have a 4, 5 or 6 only.
Nelson was not involved in the design of these models (he hired Michael Blasius for that work), so although Nelson has suggested that the pots were probably 5K, in fact they are 500 ohm pots. If you have 5k pots, of course they will work - but since we only need the range from 0-500, you just turned your bias pot from a 25 turn pot to a 2 1/2 turn pot. Which is still better than the 7/8 turn, inward facing pots that are installed.
The pots that are installed on your circuit boards now are Bourns 3386P-1-501. This is a 300V, 1/2 watt, 320 degree turn pot, and is really tricky to adjust accurately. These pots were used for a couple of reasons, that start all the way back to the original design concept. The second generation Fortes were designed as an amp that produced beautiful music at an affordable price, and to do that Michael used a lot of very smart production shortcuts such as using one single circuit board in both the right and left side of three different amps (maybe even the model 7, but I don't know that amp). Ordering 8,000 of the same board is a lot cheaper than ordering 1,000 of this and 1,000 of that, and it fit the design goals.
Anyway, because of this, and because the board has a staggered mount for the bias pots, when the board was flipped over to be used on the other channel, a vertical adjust pot would be facing downward on one side. Not helpful. Here's the pot that is in your circuit board now:
The outward facing adjustment allowed it to be mounted in any direction and still have access to the adjustment screw. Ideally, we would like to not only change these out because they get dead spots, but also make the adjusting process a lot easier. An ideal candidate for this is the Bourns 3299x-1-501, a 300V, 1/2 watt 25 turn, VERTICAL adjust trim pot that will fit right in.
The Bourns 3296x-1-501 will work as well, and is just the military spec version; the 3299x-1-501LF is the same item but meets Rohs specs. These little guys are only 2-3 dollars each, so if you're good with a soldering iron, there's almost no reason not to change them on a 30 year old amplifier.
The 3299 works best because of the leg spacing:
...which you can see is the same as the 3386. By getting a pot with a straight leg alignment, I can bend the center leg a little left or a little right to keep the screw UP on both sides of the amp.
Okay, now that you have the parts, STOP. Before you turn on the soldering gun, GET A READING ACROSS THE LEGS OF THE EXISTING POT THAT'S ON THE CIRCUIT BOARD NOW. The last thing we want to do is install a pot with a lower resistance value than what was in there to start - the extra current flow can heat things up pretty quick. As a reference (only) my transistor bias was set at 175 ohms (the new pot went in around 250) and the output offset was 254 ohms (the new one went in at 330). If for some reason you forget to do this, install both pots at 500 ohms, and open them up during final adjustment.
Your new board might look something like this:
...with those nice brass screws easily accessible now.
As you can see, the pot takes up about the same amount of space on the board, and being offset from the board, should dissipate heat a little better as well.
Hope this helps out a few guys who are still holding on to their Fortes (like me!) as we go through some well deserved maintenance after 30 years of service.
Have you found a different way, or an improvement? Include it below!
I've run across some casual discussion here on the forum regarding the bias pots in the Forte amps, but never any hard core information about how to do it. So (having done it) I thought I might be able to contribute by passing on what I've learned. Please remember, this is just one way to go about this - if you have found a different way, please add it below, you'll be helping everyone who reads this thread!
The work I did was on a model 5 and 6. The model 4 has identical circuit boards, so we know this is good information for the 4, 5, and 6. The 1 and 3 were different animals, and the 7 I'm not familiar with, so please accept this info as valid if you have a 4, 5 or 6 only.
Nelson was not involved in the design of these models (he hired Michael Blasius for that work), so although Nelson has suggested that the pots were probably 5K, in fact they are 500 ohm pots. If you have 5k pots, of course they will work - but since we only need the range from 0-500, you just turned your bias pot from a 25 turn pot to a 2 1/2 turn pot. Which is still better than the 7/8 turn, inward facing pots that are installed.
The pots that are installed on your circuit boards now are Bourns 3386P-1-501. This is a 300V, 1/2 watt, 320 degree turn pot, and is really tricky to adjust accurately. These pots were used for a couple of reasons, that start all the way back to the original design concept. The second generation Fortes were designed as an amp that produced beautiful music at an affordable price, and to do that Michael used a lot of very smart production shortcuts such as using one single circuit board in both the right and left side of three different amps (maybe even the model 7, but I don't know that amp). Ordering 8,000 of the same board is a lot cheaper than ordering 1,000 of this and 1,000 of that, and it fit the design goals.
Anyway, because of this, and because the board has a staggered mount for the bias pots, when the board was flipped over to be used on the other channel, a vertical adjust pot would be facing downward on one side. Not helpful. Here's the pot that is in your circuit board now:
The outward facing adjustment allowed it to be mounted in any direction and still have access to the adjustment screw. Ideally, we would like to not only change these out because they get dead spots, but also make the adjusting process a lot easier. An ideal candidate for this is the Bourns 3299x-1-501, a 300V, 1/2 watt 25 turn, VERTICAL adjust trim pot that will fit right in.
The Bourns 3296x-1-501 will work as well, and is just the military spec version; the 3299x-1-501LF is the same item but meets Rohs specs. These little guys are only 2-3 dollars each, so if you're good with a soldering iron, there's almost no reason not to change them on a 30 year old amplifier.
The 3299 works best because of the leg spacing:
...which you can see is the same as the 3386. By getting a pot with a straight leg alignment, I can bend the center leg a little left or a little right to keep the screw UP on both sides of the amp.
Okay, now that you have the parts, STOP. Before you turn on the soldering gun, GET A READING ACROSS THE LEGS OF THE EXISTING POT THAT'S ON THE CIRCUIT BOARD NOW. The last thing we want to do is install a pot with a lower resistance value than what was in there to start - the extra current flow can heat things up pretty quick. As a reference (only) my transistor bias was set at 175 ohms (the new pot went in around 250) and the output offset was 254 ohms (the new one went in at 330). If for some reason you forget to do this, install both pots at 500 ohms, and open them up during final adjustment.
Your new board might look something like this:
...with those nice brass screws easily accessible now.
As you can see, the pot takes up about the same amount of space on the board, and being offset from the board, should dissipate heat a little better as well.
Hope this helps out a few guys who are still holding on to their Fortes (like me!) as we go through some well deserved maintenance after 30 years of service.
Have you found a different way, or an improvement? Include it below!
Is there any such thing as "too much" inductance in a filter choke?
- By JasonWatkins
- Tubes / Valves
- 10 Replies
I've got another wacky question. Is there any such thing as "too much" inductance in a power supply choke? I ask because I have been winding my own power and output transformers for some time now with success, and just recently got around to trying an air-gapped choke. I made two revisions of it, one using a full-stack of iron from a microwave oven transformer. Original primary an two secondaries completely removed first. The second is slightly smaller. It uses a half-stack of iron out of an old APC UPS for enterprise/server use. Still pretty big though.
On the APC iron, I managed to wind 3294 turns of 28 awg. 115 ohms DC resistance. On the microwave iron, I managed 3030 turns of #28. DC resistance 147 ohms (its circumference is larger.)
My cheap LCR meter thinks they're both mosfets for whatever reason, even though it'll usually measure reasonable amounts of inductance. I tried measuring sine wave voltage drop across them, but there was no change in voltage at any frequency that I tried. So I tried injecting pulses into the circuit below and then measuring the frequency that the circuit oscillated at after the pulses. Then plug that frequency along with the known capacitance value into a LCF calculator. I don't know how accurate that was, but...
The microwave iron version returned a reading of 39.518 H. The APC iron version returned a reading of 19.225 H. That was staggering. FAR more that I am used to seeing in a power supply choke. Only time I've seen anything close to this was in a very early Atwater Kent console radio. It used a large choke along with two smallish film caps for filtering. Likely because caps were still very primitive at the time. Aside from the risk of inductive kickback (and the physical size), is there any inherent disadvantage of using a choke of that size? A choke like this would be inherently expensive to produce, but I've got a stack of free iron and a virtually infinite supply of #28 magnet wire at my disposal.
In any event, I name all my projects for record keeping. This one is called "Legato."
On the APC iron, I managed to wind 3294 turns of 28 awg. 115 ohms DC resistance. On the microwave iron, I managed 3030 turns of #28. DC resistance 147 ohms (its circumference is larger.)
My cheap LCR meter thinks they're both mosfets for whatever reason, even though it'll usually measure reasonable amounts of inductance. I tried measuring sine wave voltage drop across them, but there was no change in voltage at any frequency that I tried. So I tried injecting pulses into the circuit below and then measuring the frequency that the circuit oscillated at after the pulses. Then plug that frequency along with the known capacitance value into a LCF calculator. I don't know how accurate that was, but...
The microwave iron version returned a reading of 39.518 H. The APC iron version returned a reading of 19.225 H. That was staggering. FAR more that I am used to seeing in a power supply choke. Only time I've seen anything close to this was in a very early Atwater Kent console radio. It used a large choke along with two smallish film caps for filtering. Likely because caps were still very primitive at the time. Aside from the risk of inductive kickback (and the physical size), is there any inherent disadvantage of using a choke of that size? A choke like this would be inherently expensive to produce, but I've got a stack of free iron and a virtually infinite supply of #28 magnet wire at my disposal.
In any event, I name all my projects for record keeping. This one is called "Legato."
Occasional Big noise 100 Hz
- By spippolone
- Tubes / Valves
- 15 Replies
Hello my friends, I have a Ming tube amplifier with 300B and 845.
Sometimes a loud noise appears on the speakers at 100 Hz as if someone flipped a switch. You hear the noise... as it appears in the same mode it disappears...
With the amp open during the problem with a plastic screwdriver, I touched all the parts without anything happening. Likewise when the audio is cleaned by touching the internal wiring, nothing happens. I attach the video below where the noise suddenly appears which in this case lasts 30 seconds and then disappears on its own.
Generally the noise at 100 Hz is corrected by adjusting the HUM balance, the trimmer connected between the 47 ohm resistors on the cathode of the 300B. In fact, by adjusting the trimmer when you don't hear any background noise you can flatten the output. Here too, however, a strange thing happens: to keep the two channels silent, I detect anomalous values. In the picture attacted the value.. with the measurements at the top without valves, at the bottom with the valves mounted, doesn't it look strange??
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Thanks in advance for your precious help
Sometimes a loud noise appears on the speakers at 100 Hz as if someone flipped a switch. You hear the noise... as it appears in the same mode it disappears...
With the amp open during the problem with a plastic screwdriver, I touched all the parts without anything happening. Likewise when the audio is cleaned by touching the internal wiring, nothing happens. I attach the video below where the noise suddenly appears which in this case lasts 30 seconds and then disappears on its own.
Generally the noise at 100 Hz is corrected by adjusting the HUM balance, the trimmer connected between the 47 ohm resistors on the cathode of the 300B. In fact, by adjusting the trimmer when you don't hear any background noise you can flatten the output. Here too, however, a strange thing happens: to keep the two channels silent, I detect anomalous values. In the picture attacted the value.. with the measurements at the top without valves, at the bottom with the valves mounted, doesn't it look strange??
Login to view embedded media
Thanks in advance for your precious help
Giveaway / Raffle - Classic Aleph 30 amp boards + more (2023 Edition)
- By rhthatcher
- Pass Labs
- 72 Replies
Attachments
For Sale Celestion SL600 Loudspeakers
Attachments
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s-l1600 - 2022-12-22T023704.743.jpg -
s-l1600 - 2022-12-22T023658.133.jpg -
s-l1600 - 2022-12-22T023652.790.jpg -
s-l1600 - 2022-12-22T023647.186.jpg -
s-l1600 - 2022-12-22T023641.947.jpg -
s-l1600 - 2022-12-22T023635.952.jpg -
s-l1600 - 2022-12-22T023630.544.jpg -
s-l1600 - 2022-12-22T023625.324.jpg -
s-l1600 - 2022-12-22T023619.868.jpg -
s-l1600 - 2022-12-22T023608.350.jpg -
s-l1600 - 2022-12-22T023613.738.jpg -
s-l1600 - 2022-12-22T023600.824.jpg
Inherited DIY Tube PreAmplifier
- By Stonesilver
- Tubes / Valves
- 8 Replies
Hey all,
I recently got the chance to acquire a DIY Tube PreAmp for 300€, it was inherited to the person so they couldn’t tell me that much. I have also no clue when it comes to Tube Amplifier since this is my first one, so I’m curious if you guys can tell me some more about it, was it the money worth? what exactly is it, a rebuild? I know that it has 4 Line.Inputs + 1 Tape and a Phono (MM) Input.
Thank you in advance
I recently got the chance to acquire a DIY Tube PreAmp for 300€, it was inherited to the person so they couldn’t tell me that much. I have also no clue when it comes to Tube Amplifier since this is my first one, so I’m curious if you guys can tell me some more about it, was it the money worth? what exactly is it, a rebuild? I know that it has 4 Line.Inputs + 1 Tape and a Phono (MM) Input.
Thank you in advance
bootstrapped opamp to linearize an output stage
- Solid State
- 12 Replies
I had a wonder about bootstrapping the supplies for an opamp in an output stage to linearize it. Then I spent way too long in LTSpice...
There's a lot going on here - the input stage and VAS are pretty standard, except perhaps that the VAS is very lightly loaded at 1mA standing current and only driving an opamp input.
There is capacitive bootstrapping to provide opamp rails that track the output voltage (no attempt at considering protection circuitry yet), and this is used in a non-inverting configuration with about 1.1 gain factor. The compensation for this was mainly trial and error and I don't claim it any good other than to allow the simulation to run(!)
The opamp rails are limited to 30V by a zener and decoupled with 100nF. Since they swing with the output there is plenty of headroom for driving the drivers/output transistors right to the rails, and the 1.1 gain factor means the VAS doesn't have to get particularly close to the rails, relaxing its requirements.
I have simulated with some ripple on the +/-45V main rails (at different frequencies to allow their effects to be identified in an FFT plot). I've also simulated reactive loading by driving the opposite end of the 8 ohm load with 10V at yet another frequency.
It turns out the OS with opamp is pretty linear (IIRC about -100dB distortion) - its able to reject the simulated reactive load by 90dB or so by itself, but the overall negative feedback loop easily knocks that down out of sight:
The fourier analysis claims 0.001495% at 1kHz (40V peak) altogether upto the 80th harmonic. You can just see the 200Hz and 500Hz breakthrough from the rails in this plot, attenuated from 1V on the rails to about 30uV at the output.
The overall gain is x 20 (26dB), and from 45V rails with 1V ripple (ie dipping to 44V) it clips at around 42V peak.
The elephant in the room is how robust can such a scheme be made, given any fault on the output risk putting 45V or more onto the opamp in various ways.
There's a lot going on here - the input stage and VAS are pretty standard, except perhaps that the VAS is very lightly loaded at 1mA standing current and only driving an opamp input.
There is capacitive bootstrapping to provide opamp rails that track the output voltage (no attempt at considering protection circuitry yet), and this is used in a non-inverting configuration with about 1.1 gain factor. The compensation for this was mainly trial and error and I don't claim it any good other than to allow the simulation to run(!)
The opamp rails are limited to 30V by a zener and decoupled with 100nF. Since they swing with the output there is plenty of headroom for driving the drivers/output transistors right to the rails, and the 1.1 gain factor means the VAS doesn't have to get particularly close to the rails, relaxing its requirements.
I have simulated with some ripple on the +/-45V main rails (at different frequencies to allow their effects to be identified in an FFT plot). I've also simulated reactive loading by driving the opposite end of the 8 ohm load with 10V at yet another frequency.
It turns out the OS with opamp is pretty linear (IIRC about -100dB distortion) - its able to reject the simulated reactive load by 90dB or so by itself, but the overall negative feedback loop easily knocks that down out of sight:
The fourier analysis claims 0.001495% at 1kHz (40V peak) altogether upto the 80th harmonic. You can just see the 200Hz and 500Hz breakthrough from the rails in this plot, attenuated from 1V on the rails to about 30uV at the output.
The overall gain is x 20 (26dB), and from 45V rails with 1V ripple (ie dipping to 44V) it clips at around 42V peak.
The elephant in the room is how robust can such a scheme be made, given any fault on the output risk putting 45V or more onto the opamp in various ways.
Analog Crossover Network: Basic Kit: parts shortage
- By audiorasp
- The diyAudio Store
- 0 Replies
Hello,
I’ve recently received the Analog Crossover Network: Basic Kit purchased from the diy Audio store to build the Lxmini crossover. However, it came with the pcb, transistors, and only 8- 100 ohm “tweaking resistors” as shown in the image. Is it possible to get another set of transistors with the 16 resistors?
George
I’ve recently received the Analog Crossover Network: Basic Kit purchased from the diy Audio store to build the Lxmini crossover. However, it came with the pcb, transistors, and only 8- 100 ohm “tweaking resistors” as shown in the image. Is it possible to get another set of transistors with the 16 resistors?
George
Rohde & Schwarz UPV / UPP Audio Analyzer Thread
- By electronic
- Equipment & Tools
- 5 Replies
