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2nd sse has suddenly developed a problem

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I was careful and neat with this build and it has worked fine from the first time I powered it up over 6 months ago. This week I turned it on and as soon as the tubes warmed up I started hearing a soft rapid putt putt sound in the center between the speakers so it must be coming from both channels. I went ahead and started some music playing and it sounded recessed or far away.

So far I have swapped out the rectifier tube and the driver tube and that made no difference. I tried disconnecting the auxiliary capacitor and that made no difference either. I put my Pass ACA's in the system to make sure the noise was not coming from upstream and it wasn't.

I can not think of anything on the board that could make a putt putt sound. One article I read suggested that type sound could come from capacitors.

Has anyone experienced this type of fault?
I have never had that happen, or heard of it.

Let's try to find out where it's coming from.

First pull the input cables. Does the putt putt still happen?

If not try connecting a CD player or a phone or iPAD directly to the SSE inputs with no other connections.

If it still happens, pull the 12AT7 and try again. Power down the amp to pull the tube.

If that stops the putt putt I would suspect the 10M45's or possibly a coupling cap. You are in the US, so I assume that you got your 10M45's from a major distributor, they are probably OK. Builders in Europe have been plagued with fake parts, especially on Ebay or Ali.

Also try pulling one output tube at a time. Heater to cathode leakage in one tube can affect the whole amp.

Make sure that one of the output tubes is not red plating. A bad tube will over stress the cathode bypass cap causing weird problems.
Sorry I just noticed your reply

I went ahead and replaced c1 and c2 with new caps. I tested the pulled caps with an ohm meter and they seemed fine. The putt putt putt noise still persists in both channels. When I swap in another amp there is no noise. That is why I am thinking it is the sse. Since the noise is in both channels I was thinking it must be something shared in the power supply. There is the small c3 cap I could replace.

The coupling caps are obbligatos I got from partsconnexion. I got the ccs chips from mouser I believe.

I will try your suggestions first.
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Well knock me over with a feather

I started using ip over power adapters a couple of months ago. I just noticed when I started a track on my network player the the speed of the putt putt noise changed then it suddenly hit me that the amp is picking up noise from the ip over power adapter in the next room. I unpluged the adapter and no noise.

Since the Pass ACA's use switching power supplies they were somewhat immune to the noise I guess.

I need to do some experiments to see if I can stop the noise. I would like to continue using the ip over power adapters if possible.

Thanks George and everyone for your suggestions.
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