The power on LED you mean?
No concern whatsoever. Probably just a different batch or manufacturer, however you can tweak the resistor feeding either LED to equalise the levels or if they are very different in appearance (colour temperature) you could replace both with two known to be the same. Also check the series resistor feeding each is the same value (not tolerance, I mean a wrong value)
No concern whatsoever. Probably just a different batch or manufacturer, however you can tweak the resistor feeding either LED to equalise the levels or if they are very different in appearance (colour temperature) you could replace both with two known to be the same. Also check the series resistor feeding each is the same value (not tolerance, I mean a wrong value)
Yes, the power on LED. I assumed there is no issue, but figured it was worth asking. Every time I ask a question, I learn something. I generally try to research a question before asking then ask in case there is something I'm missing.
As always, I appreciate the response!
As always, I appreciate the response!
I'll just put a little piece of duct tape over one LED on each amp and pretend they are FW!Classic LED issue. If you have 2 LEDs you have to match them carefully or you get the call...
The FW amplifiers have switched to 1 LED by way of addressing it.
I ordered 2 Amp Camp Amps ( can't wait ) and am starting to think about what speakers to get that will be a good match. I will use them primarily for analog synths and analog drum machine, and would like to reproduce the original signal source as clean as possible. ( like the old school passive Yamaha studio monitors )
I don't know much about speakers, and am wondering if there are some 'go to' speakers I should look at. I noticed Yamaha no longer sells passive studio monitors, and I may want some a bit more substantial anyways. Currently, I'm looking at 'Klipsch Reference Premiere RP-8000F II' and maybe adding a powered class D Klipsh sub if needed. Are there other speakers which have been a good match? ( I'm also looking at the OpenSourceMonkeyCoffin build but those may be a bit expensive to build these days )
I can run my 2 amps as monoblocks or bi-amps if speakers support it.
I don't know much about speakers, and am wondering if there are some 'go to' speakers I should look at. I noticed Yamaha no longer sells passive studio monitors, and I may want some a bit more substantial anyways. Currently, I'm looking at 'Klipsch Reference Premiere RP-8000F II' and maybe adding a powered class D Klipsh sub if needed. Are there other speakers which have been a good match? ( I'm also looking at the OpenSourceMonkeyCoffin build but those may be a bit expensive to build these days )
I can run my 2 amps as monoblocks or bi-amps if speakers support it.
Can't recommend speakers, but just thought I'll make you aware that the preamp you use should have some gain otherwise you'll be disappointed in the ACA's - even if you use quite sensitive speakers. And while I'm mentioning speaker sensitivity, you want at least 94dB, preferably 100dB or thereabouts.
After several years of happy performance, one of my two v1.6 ACÁ monoblocs is nearly silent. I get proper voltage readings on Q2, but only millivolt readings on Q1 on one board. On the other board, I get proper voltages on Q2 and proper voltage on S and D of Q1, but only 2.56v on gate (it’s supposed to be 4.1-4.7v). I’m nervous about poking my MM probes around the smaller points, but will do it if it helps. I’m not sure photos will help. Any thoughts?
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And just as important, measure the actual supply voltage at the amp.
Is that the other board in the faulty ACA or the other working ACA. Just to be clear
2.56v volt is low for the specified FET and suggests near zero bias current. Check the supply voltage under load first.
You are going to have to get proactive and take some key voltage measurements
You must measure on the board itself to confirm the 24 volt is present. Double check the output voltage on the junction of the 0.47 and 0.68 ohm resistors really is around 12 volts.
Next key measurement is the voltage between Q1 Drain and Q2 Source. This is the voltage across the series pair of 0.47/.0.68 ohms. It should be around 0.9 to 1 volt give or take.
If all those are correct then the amp is essentially working OK.
Make sure there is nothing external at fault like a shorted speaker cable or problem with an input.
You must measure on the board itself to confirm the 24 volt is present. Double check the output voltage on the junction of the 0.47 and 0.68 ohm resistors really is around 12 volts.
Next key measurement is the voltage between Q1 Drain and Q2 Source. This is the voltage across the series pair of 0.47/.0.68 ohms. It should be around 0.9 to 1 volt give or take.
If all those are correct then the amp is essentially working OK.
Make sure there is nothing external at fault like a shorted speaker cable or problem with an input.
Also measure the Vgs of Q1 and Q2.
The Vgs of Q1 is helpful in checking the health of the input JFET. Does adjusting the pot change Q1 Vgs? What are the maximum and minimum Vgs when adjusting the pot? For ease of measurement, the voltage may be measured across R9 (1k resistor).
Please post all of the voltage measurements for both channels. Do not just post numbers are ok. Seeing the actual numbers is very helpful for troubleshooting.
The Vgs of Q1 is helpful in checking the health of the input JFET. Does adjusting the pot change Q1 Vgs? What are the maximum and minimum Vgs when adjusting the pot? For ease of measurement, the voltage may be measured across R9 (1k resistor).
Please post all of the voltage measurements for both channels. Do not just post numbers are ok. Seeing the actual numbers is very helpful for troubleshooting.
Mooly and Ben Mah,
Thanks so much for lending your expertise. Here are the measurements, using the points shown in 6L6’s guide for the v1.6. (I will just note that with a little more care I got stable readings that I didn’t achieve earlier.
Board 1
Q1 — S, 4mV; D, 11.5V; G, 4.4V. Vgs is 4.42V, pot ranges from .6 to 4.5
Q2 — S, 12.5V; D, 23.7V; G, 16.9V.
Q4 @ D, 23.75V
R15 @ b, 12.3V; @e, 11.5V
R5, 16.7V
R 9, 4.4V
R 10, 4.0V
Board 2
Q1 — S, 15.6mV; D, 11.8V, G, 4.5V. Vgs is 4.53, pot ranges .6 to 4.67
Q2 — S, 12.6V; D, 23.7V; G, 17.1V
Q4@D, 23.7V
R15@b, 12.3V; @e, 11.8V
R5, 17.0V
R9, 4.5V
R10, 4.15V
i do not know how to take the measurement at the 5W resistors or Between Q1D and Q2S. I switched speaker cables, and also input, both work fine.
Thanks so much for lending your expertise. Here are the measurements, using the points shown in 6L6’s guide for the v1.6. (I will just note that with a little more care I got stable readings that I didn’t achieve earlier.
Board 1
Q1 — S, 4mV; D, 11.5V; G, 4.4V. Vgs is 4.42V, pot ranges from .6 to 4.5
Q2 — S, 12.5V; D, 23.7V; G, 16.9V.
Q4 @ D, 23.75V
R15 @ b, 12.3V; @e, 11.5V
R5, 16.7V
R 9, 4.4V
R 10, 4.0V
Board 2
Q1 — S, 15.6mV; D, 11.8V, G, 4.5V. Vgs is 4.53, pot ranges .6 to 4.67
Q2 — S, 12.6V; D, 23.7V; G, 17.1V
Q4@D, 23.7V
R15@b, 12.3V; @e, 11.8V
R5, 17.0V
R9, 4.5V
R10, 4.15V
i do not know how to take the measurement at the 5W resistors or Between Q1D and Q2S. I switched speaker cables, and also input, both work fine.