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What are the signs of caps going in an Amp?

I have been blaming streaming since I am new to streaming, like a couple weeks in, new. I was away for a for while as our home was being built and my gear was inactive. I have a Classe CA-151 amp and Classe SSP25 pre that I only use for 2 channel anymore and they are approaching 20 years old. So I bought a Node 2i and have been enjoying my Qobuz trial. It started intermittently the last few nights where I start hearing static, muffled sound, almost like a radio station going softly in and out of tune. I have been blaming it on streaming and wifi or ethernet connection. Someone pointed out it may be a cap starting to go bad. I checked all the other connections and everything is tight and good. What are the signs of a cap going bad? Is it constant or intermittent? Next time it happens I am going to switch over to CD to rule out streaming. When it happened last night I switched to Tidal to rule out Qobuz, and then switched to my MacBook to rule out the Node and it was still there. I did not have the CD player connected at the time otherwise I would have switched, but that is my next step. 
Thanks!
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atmasphere's avatar
atmasphere
11,844 posts
 
If a filter capacitor were failing in the power supply, its most likely sign would be a hum that shows up, possibly going away if you cycle it off and on, but returning again in due time.


This does not sound like a power supply filter cap failing. It could be the amp, but seems unlikely a filter cap is doing it.
kijanki's avatar
kijanki
4,428 posts
 
I had once an amp with old caps and after replacement bass got more punchy/dynamic.  I don't see how power supply caps can make "muffled sound", but perhaps other (than power supply) electrolytic caps are failing (or something else).  In ideal case caps should last 40-50 years, but if your amp gets warm, then 20 might be good time to replace them (noticeable improvement).
cd318
2,636 posts
 
Great question.

Because it could happen sooner or later.

I knew a case where a power supply capacitor leaked inside 2 years on a big name integrated amplifier.

It was making a constantly buzzing sound on both channels whilst still playing music. In fact the buzzing was present on all inputs regardless.

It’s probably dangerous to generalise the symptoms because it might depend upon where the leaking capacitors were.

My current amp had replacement capacitors according to the previous owner.

I don’t know if it’s unusual but there’s literally dozens of capacitors inside this particular model. I can’t remember ever seeing so many inside any other amp.

I can also remember when Dell had an issue with leaking caps on their desktops some 15 years ago. Thankfully they seem to have got it sorted pretty soon after and it’s never happened again.

Some products on the other hand seem to be immune. My previous amp (Naim pre/power) was left powered on for over 10 years without a hint of a problem.
georgehifi's avatar
georgehifi
10,312 posts
 
What are the signs of caps going in an Amp?
First thing you notice if you open the amp, is that the cap top will start to bulge a little, maybe even the sides, some have an X stamped into the top this is a safety pressure release valve, or you see some wetness around the base on the PCB where the electrolyte has leaked out.

Cheers George
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