Nad c325 - noise on one channel
I ask for your help to try to find out the cause of this problem.
Intermittent popcorn-like noise on the left channel.
It is more evident if I leave the amplifier unplugged for several days.
The noise tends to decrease if you leave it running for a long time, after 2 or 3 hours, it decreases considerably but does not disappear.
The noise is also audible through the headphones.
It is independent of the source and volume of the sound.
Curiously in standby the noise persists in the headphones but not in the speakers. ????
I ask for your help to try to find out the cause of this problem.
Intermittent popcorn-like noise on the left channel.
It is more evident if I leave the amplifier unplugged for several days.
The noise tends to decrease if you leave it running for a long time, after 2 or 3 hours, it decreases considerably but does not disappear.
The noise is also audible through the headphones.
It is independent of the source and volume of the sound.
Curiously in standby the noise persists in the headphones but not in the speakers. ????
The headphone output comes from the power amplifer output through a two resistor attenuator,
so the noise must be in both the speaker and headphones.
The power amplifier circuit has metal film resistors, and a fair number of semiconductors.
Localizing the noise to one part or connection would be rather difficult, but it does seem like
it could be a semiconductor, although metal film resistors can also develop such noise.
Hum is likely to be an electrolytic capacitor developing high ESR. especially the 15,000uF pair.
so the noise must be in both the speaker and headphones.
The power amplifier circuit has metal film resistors, and a fair number of semiconductors.
Localizing the noise to one part or connection would be rather difficult, but it does seem like
it could be a semiconductor, although metal film resistors can also develop such noise.
Hum is likely to be an electrolytic capacitor developing high ESR. especially the 15,000uF pair.
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Sounds to me to be a perfect candidate for very sparing application of freezer spray on suspect parts. Apply a drip at a time on parts, don't blast a whole area.
It could be anything. Do not overlook any small compressed disc type capacitors as they can be troublesome. It could be a transistor, any hot running devices would be suspect which would probably be the VAS stage in the amp.
It could be anything. Do not overlook any small compressed disc type capacitors as they can be troublesome. It could be a transistor, any hot running devices would be suspect which would probably be the VAS stage in the amp.
It could be a transistor, but it could be almost anything.
I was about suggest cold shot, but Mooly beat me. I'd also tap around with a wooden stick. Pure guess, I'm also suspicious of the CON8/CON9 connector pair, as global feedback passes though. Maybe contact cleaner for good measure.
Good luck!
I was about suggest cold shot, but Mooly beat me. I'd also tap around with a wooden stick. Pure guess, I'm also suspicious of the CON8/CON9 connector pair, as global feedback passes though. Maybe contact cleaner for good measure.
Good luck!
