Here are the substitutions on the PCB. I believe they are in line with TungstenAudio's recommendations. I have confirmed that these are the actual substitutions on the PCB.
C1: 5600 uF, 35V; Nichicon KG series "Gold Tune" (updated from original upgrades)
C2: 1000 uF, 16V; Nichicon RNL series Aluminum Organic Polymer
C4: 100 uF, 35V; Nichicon RL8 series Aluminum Organic Polymer
R3 & R4 .56 Ohm Resistors (RSF200JR-73-0R56 2W)
R11: 20 kOhm, 1/4W, 1% metal film
R12: 90.9 kOhm, 1/4W, 1% metal film
IXTQ75N10P Mosfet at Q1
On board add-on components
C101: 10 pF, 500V, 5% Silver Mica; added in parallel w/ R12
Off board substitution
Filter drain point of Q4: 68.1 kOhm, 1/4W, 1% metal film.
I still have test the gain on the amplifier. And I need to check the switch, although I am unsure precisely how to do that.
A few close up pictures of one PCB.
C1: 5600 uF, 35V; Nichicon KG series "Gold Tune" (updated from original upgrades)
C2: 1000 uF, 16V; Nichicon RNL series Aluminum Organic Polymer
C4: 100 uF, 35V; Nichicon RL8 series Aluminum Organic Polymer
R3 & R4 .56 Ohm Resistors (RSF200JR-73-0R56 2W)
R11: 20 kOhm, 1/4W, 1% metal film
R12: 90.9 kOhm, 1/4W, 1% metal film
IXTQ75N10P Mosfet at Q1
On board add-on components
C101: 10 pF, 500V, 5% Silver Mica; added in parallel w/ R12
Off board substitution
Filter drain point of Q4: 68.1 kOhm, 1/4W, 1% metal film.
I still have test the gain on the amplifier. And I need to check the switch, although I am unsure precisely how to do that.
A few close up pictures of one PCB.
I will be away from a computer for a while, but Ben and others can certainly fill in any gaps.
Easy tone generator with little risk - Phone and a downloadable app for a tone gen ... use that as the input. If you don't have a way to do it on your phone, you can probably get something to play through your computer / Sonos. Set it for 60Hz and turn up the volume a bit.
No speakers hooked up.
Measure the output of the phone / tone generator using DMM set to ACV. It will likely be < 1V from your phone, and with the volume cranked out of the Sonos... it could be ~2V.
Connect the phone (or other) to the amp. Turn on the tone.
Using your wiring diagram, trace the signal / follow the input all the way to the amp boards. Make sure that the switch works appropriately for both input types. If you have the same voltage where the input wiring connects to the amp boards, you know that you likely did all your input wiring correctly.
Turn on the amp. Measure the ACV at the speaker terminals using the various switch positions as appropriate and moving the DMM probes as appropriate to measure the output.
Report back:
Gain is output / input.
Typed that pretty quickly, but if you need any clarity on exactly where to place probes etc., definitely ask.
That will help narrow things down a bit in addition to the measurements that Ben requested. I haven't had time to review that.
Easy tone generator with little risk - Phone and a downloadable app for a tone gen ... use that as the input. If you don't have a way to do it on your phone, you can probably get something to play through your computer / Sonos. Set it for 60Hz and turn up the volume a bit.
No speakers hooked up.
Measure the output of the phone / tone generator using DMM set to ACV. It will likely be < 1V from your phone, and with the volume cranked out of the Sonos... it could be ~2V.
Connect the phone (or other) to the amp. Turn on the tone.
Using your wiring diagram, trace the signal / follow the input all the way to the amp boards. Make sure that the switch works appropriately for both input types. If you have the same voltage where the input wiring connects to the amp boards, you know that you likely did all your input wiring correctly.
Turn on the amp. Measure the ACV at the speaker terminals using the various switch positions as appropriate and moving the DMM probes as appropriate to measure the output.
Report back:
- input voltage (voltage from the source / tone generator)
- input signal voltage to both amp boards where the wires connect to the amp boards using all switch positions as appropriate. One switch position won't yield proper values without the amp turned on, but don't worry about that.
- output voltages with the switch in all three positions. Left and right as appropriate and bridged as appropriate.
Gain is output / input.
Typed that pretty quickly, but if you need any clarity on exactly where to place probes etc., definitely ask.
That will help narrow things down a bit in addition to the measurements that Ben requested. I haven't had time to review that.
I finally am finally getting back to this. However sitting here with my multimeter, I am not sure exactly where to place the probes to complete the testing. I thought I did, but will take up the offer of help. Sorry for putting on full display my lack of knowledge.
Tom,
Is that correct that you have a 68.1K resistor on the drain of Q4? That is way too high of a value. If you are running at 24 volts, a 200 ohm resistor is
plenty for some some filtering to the power supply of Q4, or if you were using a higher voltage like 28 or 30 volts, that resistor will also offer
over-voltage protection for Q4. That high of a value will cause Q4 to not function as it should. If you are using a 24 volt supply, try a 200 ohm resistor
in line with the Q4 drain, and remove that 68.1K resistor.
Is that correct that you have a 68.1K resistor on the drain of Q4? That is way too high of a value. If you are running at 24 volts, a 200 ohm resistor is
plenty for some some filtering to the power supply of Q4, or if you were using a higher voltage like 28 or 30 volts, that resistor will also offer
over-voltage protection for Q4. That high of a value will cause Q4 to not function as it should. If you are using a 24 volt supply, try a 200 ohm resistor
in line with the Q4 drain, and remove that 68.1K resistor.
Good catch. A 68.1k resistor would drop too much voltage, leaving not much for the jfet, close to nothing.
What confuses me now is the voltage drop that was measured across R9 (5.28V left, 5.17V right). That looks unlikely if the jfet was not getting much voltage, so the measurement was most likely not correct.
What confuses me now is the voltage drop that was measured across R9 (5.28V left, 5.17V right). That looks unlikely if the jfet was not getting much voltage, so the measurement was most likely not correct.
I see that when I copied and pasted over the parts list I failed to correct the resistor value to what I actually used. I did use a 200 ohm resistor.
Tom,
Is your ACA version 1.8? Check the wiring on the left channel going to the XLR. The right channel connection looks right, but the left doesn't
look like it is attached to the right place. Should be attached to pin #3.
Is your ACA version 1.8? Check the wiring on the left channel going to the XLR. The right channel connection looks right, but the left doesn't
look like it is attached to the right place. Should be attached to pin #3.
I may be wrong, but the PCB reflects 1.6 but the kit is the 1.8 version.
Regarding the wiring here is a better pic. I think I have this right. Please see below:
Regarding the wiring here is a better pic. I think I have this right. Please see below:
I have also done some testing as requested. Downloaded a signal generator app and connected the IPAD directly to the amplifier via RCA. Here the results:
I also rechecked the bias are both 12 V.
One last comment is that with the amp off, if the room quiet,
I can just hear the music playing, that is true if the Sonos streamer is connected directly or if ai run the signal through the Kong preamp. Then when the amp comes on the signal gets louder but is still very low. Using the Korg with my 2 Watt Decware amp I can’t turn the volume more that half way before it is too loud with the same speakers.
- input voltage (voltage from the source / tone generator). I did by connecting my MM probes to the RCA jacks. One to the pin and the other to the outer ring.
- input signal voltage to both amp boards where the wires connect to the amp boards using all switch positions as appropriate. One switch position won't yield proper values without the amp turned on, but don't worry about that. I did this by connecting the black probe to the speaker ground wire running and the red to the input +.
- output voltages with the switch in all three positions. Left and right as appropriate and bridged as appropriate.
I also rechecked the bias are both 12 V.
One last comment is that with the amp off, if the room quiet,
I can just hear the music playing, that is true if the Sonos streamer is connected directly or if ai run the signal through the Kong preamp. Then when the amp comes on the signal gets louder but is still very low. Using the Korg with my 2 Watt Decware amp I can’t turn the volume more that half way before it is too loud with the same speakers.
Tom,
Try connecting the second white wire from the positive left RCA down to where you have the gray wire connected to pin 3 of your XLR instead of where
it is currently connected.
Try connecting the second white wire from the positive left RCA down to where you have the gray wire connected to pin 3 of your XLR instead of where
it is currently connected.
I moved the white wire and connected it to where the grey wire is. The left speaker no longer works with the switch in the top and middle locations. In the bottom position neither speaker works.
Tom,
For heavens sake! I was looking at the wiring diagram changes for the 1.8 version, so my apologizes for being of no help!
I have the 1.6 version, but never used the rear switch, so only had the DIY diagram to offer. Will look some more!
For heavens sake! I was looking at the wiring diagram changes for the 1.8 version, so my apologizes for being of no help!
I have the 1.6 version, but never used the rear switch, so only had the DIY diagram to offer. Will look some more!
TomR, You probably did not confirm resistor values before installing on circuit board.
Check the value of R12:
Check the value of R12:
and Tom, what is the value of your R10. If R10 and R12 got switched you would kill all of your gain
good one Ben...that has got to be it 🙂
good one Ben...that has got to be it 🙂