I recently picked up a NAD 3020B that is near mint cosmetically and sounds great but when I switch it off, there is a high pitched crack sound from the right channel.
Observations
1) The noise is loudest when the volume setting is lowest.
2) With RCA interconnects replacing the U shaped metal bridges between pre and power, the sound was quieter but not absent.
3) When I cross connect the pre and power amps, the sound moves to the left channel.
4) When I use another preamp with the NAD power amp, the problem vanishes.
5) When I use the NAD preamp with another power amp the problem is there.
It appears that the problem is in the right channel preamp. Beyond that, I am guessing.
Can anyone suggest likely potential causes or solutions?
Observations
1) The noise is loudest when the volume setting is lowest.
2) With RCA interconnects replacing the U shaped metal bridges between pre and power, the sound was quieter but not absent.
3) When I cross connect the pre and power amps, the sound moves to the left channel.
4) When I use another preamp with the NAD power amp, the problem vanishes.
5) When I use the NAD preamp with another power amp the problem is there.
It appears that the problem is in the right channel preamp. Beyond that, I am guessing.
Can anyone suggest likely potential causes or solutions?
energyandair said:
Hi,
I agree with you. On site http://www.gmweb.btinternet.co.uk/others.htm you can download schematic, use hand multimetar and measure DC voltage (without signal - pot on minimum) on preamps: base and emiter Q505,6, base and collector Q503,4. I suspect that problem is in some caps fault in signal path.
Regards
noise
Energyandair,
Good thinking to isolate it in the preamp channel. Let's try to get a bit further.
Is it a single "crack" or does it sound like a sliding tone that dies out in a short time?
Is it only in one channel really or also in the other but much less loud (you may need to listen to both speakers separately to accurately verify this).
Jan Didden
Energyandair,
Good thinking to isolate it in the preamp channel. Let's try to get a bit further.
Is it a single "crack" or does it sound like a sliding tone that dies out in a short time?
Is it only in one channel really or also in the other but much less loud (you may need to listen to both speakers separately to accurately verify this).
Jan Didden
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