McIntosh C-32 Pop at Power Off

[BargainBrad]

Hi all. I recently finished restoring a Macintosh C-32 pre-amplifier, including new electrolytic, capacitors and ribbon connectors. It is working beautifully and sounds great. The only issue I have is that I get a fairly load pop at power off. I hear the pop regardless of output, including the monitor speaker ouputs, and the volume of the pop changes when I turn the volume knob, but does not totally disappear on the lowest volume setting. Does anyone have any suggestions as to the most likely cause? I could probably live with this, but it is going to eat at me given how many hours I put in on this project.

 

[avionic]

Shut down power amp first.

 

[BargainBrad]

Shut down power amp first.

I always do and still get a fairly loud pop, which is concerning, because I can't imagine how bad it would be if the power amp was on.

 

[RVT1K]

No experience but since it it effects all outputs -I'm assuming both channels- my guess is something in the power supply side. I know that is very vague and bordering on useless but that is where I would start.

I turn my amps off with music still playing. I lower the volume -if things were jumping-, hit the power switches -bi-amping-, and wait for silence. Then I power off my pre amp.

 

[avionic]

my guess is something in the power supply side.

Collapsing DC power supply causes severe DC offset. I'd be looking at the power on/off muting circuitry.