Thanks for your response, my reasoning for a multi-capacitor setup comes exclusively from the information passed on by an Engineer at Peavey. Ive only just started repairing amps and electronics at a hobby level so I cant comment on this particular capacitor setup that he describes. If I hadn't found this information online then I would most likely have just replaced the components 1:1
Ive copied the exact quote so people can better understand what im trying to achieve and where i got the idea. This capacitor setup only mentions the coupling cap and it was me who thought about doing a similar job with the 6000uf capacitor considering I need to change it out anyway.
Quote:
"I'll also share the rest of my conversation with Bobby Baldwin (@BbbyBld) about this amp:
There were two Centuries. The early one had a discrete preamp that ran off of a single +50V supply.
I built a really simple preamp with discrete transistors and was blown away at how fast and present the response was. It occurred to me that each opamp stage probably has close to 10 transistors inside in the audio path, and a modern preamp can easily use a dozen opamp stages. Each transistor adds a little delay and a little distortion.
The later Century (C1980) used the 200H module, the preamp used opamps and they ran off of +/-15V.
The power module [in the older Century] is one of the original Peavey solid state power amps by the way.
Hartley Peavey contracted a company out of Alabama to design it. That company was Orrtronics, and their claim to fame was manufacturing recording tape.
It is a very early, primitive design.
It was used in various products up to about 1980, even though Peavey had far more advanced designs during that time designed by Jack Sondermyer, the father of modern solid state power amp technology.
The capacitively coupled output is part of the "crudeness" of this design, so I'd recommend modifying that part.
Basically, capacitors pass higher frequencies with ease, but lower frequencies have a harder time passing through. This means that your power amp puts out a little less in the low frequency range than it does at 1K.
The other thing that happens is that when you start to clip the power amp with low frequencies, instead of a pleasant growl, you get a nasty buzz sound. The way to fix that is to use a larger capacitor, but...
The other thing is that capacitors can be inductive, especially electrolytic caps, because the plates are rolled into a coil. This means that your power amp also puts out a little less in the upper audio range because the inductance starts to factor in a little. Inductors pass lower frequencies freely, but tend to block higher frequencies. Just using a larger capacitor can increase the inductance because the plates can be longer, thus more inductance.
Ultimately, the output response of your power amp is sort of a bell curve. This capacitor is also subject to high ripple current (rapid charging and discharging) because there is pure, high AC current passing through it all the time. This can dramatically shorten the life of a capacitor.
The way to get around all of this is to use multiple capacitors in parallel, one of them being a film capacitor so there is no high frequency degradation.
The inductance will go down because inductors in parallel divide. The ripple current will also divide so you won't be stressing a single cap.
So, if you end up beefing up the output coupling cap. it will add some low end.
There may be a little bit of crossover distortion, but that is normal for these modules, and it improves once it heats up, which is also typical of many passively cooled SS power amps.
If you've had to replace the original output transistors, you may want to add a 0.1uF cap. across the speaker output jacks.
It would help to clean up the output signal when using the modern output transistors by dampening out instability.
[After completing these mods, I commented on how loud the Century is for a humble 100-watt amp. Bobby replied as follows:]
Modern power amps are biased class B, but also have a whole lot of gain and lots of negative feedback to get rid of crossover distortion, which in turn gives them a high damping factor. Your amp does not have a lot of gain or feedback, and has a low damping factor. That's where I think the loudness comes from."