Question on Capacitors

[OverAnalyst]

Hi All,
I've never had a strong electrical background, but I'm certainly getting more interested as I tinker more with my audio setup. I do have a question on capacitors. If a capacitor is undersized (or perhaps loses its capacitance?) in a solid state power amp, what can you expect in terms of diminished sound quality? Is it that you just lose some of the low end (low frequency) coming out of the speakers?

And vice versa, if a capacitor is oversized, does that mean you have extra energy stored in the capacitor that's not being used thus you have an inefficient system?

[OverAnalyst]

sorry, not sure if this belongs in the technical forum...

[Paul Birkeland]

Here's a before and after for a solid state Pioneer amp I recapped playing into a test woofer.  You can definitely hear this!

[EricS]

If you are working with a Class-A amps (runs hot with high, constant current draw), undersized or aged caps will cause audible hum on the speaker because they do not provide enough power supply ripple storage/filtering. 

With Class-B amps (typical consumer gear), caps that are too small will cause the amp to not be able to deliver it's rated power output.   This is pretty evident in the images that Paul posted above.

[OverAnalyst]

Oh wow, thanks for the visual. Curious, how old is the Pioneer amp? I have a Dynaco ST80 that I don't think has ever been recapped, and at the same time I think it sounds good. BUT, if I recap, will it sound better?

[Paul Birkeland]

Oh wow, thanks for the visual. Curious, how old is the Pioneer amp? I have a Dynaco ST80 that I don't think has ever been recapped, and at the same time I think it sounds good. BUT, if I recap, will it sound better?

The Pioneer was an SA-9500 MK-II.

The ST-80 is a bit of an oddball because you are relying on those big power supply caps to also act as an inductor former.  People tend to gut them and put in more modern circuitry.

[OverAnalyst]

Thanks PB/Eric. I think I know what I need to focus on for next upgrades.