Which caps make the most audible difference?

[TDWesty]

I am trying to get a better understanding of which components are most critical to audio quality in an amp. I've read about all the various exotic caps, and things like replacing caps "in the signal path" especially, and other common words of advice.
If my understanding of "in the signal path" is correct, there aren't all that many EL caps in the signal path in a typical amp (NAD 3020 in this case). Is this correct? I could find only one in the pre-amp section, and one more early on in the LAB IN of the main amp section . I've replaced both, along with the remaining EL caps in the pre-amp section (all were 47uF 6.3V).
Should I be looking at Tantalum and ceramic disc caps also?

I've replaced all the big PSU and reg PS caps already, which opened things up quite a bit, and provided a bit more punch with more controlled bass. Are my gains beyond this point likely to be very minimal, ie: difficult to discern without an A-B test? I have an NAD 3125 which still sounds more refined/detailed than the 3020 at this stage, so I can do a comparison of sorts. But maybe this isn't a fair or useful comparison, since they use different output sections & power transistor types?

[Nordic]

Consider the amplified output... sometimes many times the voltage of the input... where did the power come from.... everything is in the signal path...which i think is more of a network than a path anyway... and I'm still a noob.

[lineup]

Originally posted by TDWesty
I am trying to get a better understanding of which components are most critical to audio quality in an amp. I've read about all the various exotic caps, and things like replacing caps "in the signal path" especially, and other common words of advice.
If my understanding of "in the signal path" is correct, there aren't all that many EL caps in the signal path in a typical amp (NAD 3020 in this case). Is this correct? I could find only one in the pre-amp section, and one more early on in the LAB IN of the main amp section . I've replaced both, along with the remaining EL caps in the pre-amp section (all were 47uF 6.3V).
Should I be looking at Tantalum and ceramic disc caps also?

I've replaced all the big PSU and reg PS caps already, which opened things up quite a bit, and provided a bit more punch with more controlled bass. Are my gains beyond this point likely to be very minimal, ie: difficult to discern without an A-B test? I have an NAD 3125 which still sounds more refined/detailed than the 3020 at this stage, so I can do a comparison of sorts. But maybe this isn't a fair or useful comparison, since they use different output sections & power transistor types?

First, about tantalum and ceramics.
There is very limited used for those in modern audio amplifiers.
Still when no good alternative is to be found for very small capacitors, say 5-100 pF, we have to use ceramics.
Like for compensation caps and in feedback loop.

About replacing caps in older amplifier and make it better.
I think it is like this.
You can not improve amplifier, by changing caps. Not very much.

But you can make it start working as it should.
If supply big caps are dry and not too large and if other electrolytic caps are bad by age
the amplifier would not perform at its level.
Re-capping can put it back to perform at its best.

Small electrolytic capacitors in signal path should be replaced with FILMCAPS.
You can see if it is a polarized cap.
They have + and - polarity marks.
Replace with Polyester, MKT or Polypropylene.


If this would make a change you can actually hear is not easy to say.
Most times I would say it is so small improvement we can't hear it.
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Summary:
- Recapping an oldie will make it back to normal quality.
If capacitors were in bad condition.
- But to make the amplifier better than it was, when new,
is not very probable, by just changing capacitors.
- One exception is, when the original design, did not have very much big electrolyts in Power Supply.
Adding a bit more would possibly make amp 'better'.
At least this can not make the amp worse

lineup

[djk]

Try replacing the 1000µF 6.3V cap in the feedback loop.

[zBuff]

http://gnu.295.ca/~peak/audio.html#2

http://www.tnt-audio.com/ampli/nad3120upgrade_e.html

[TDWesty]

Originally posted by djk
Try replacing the 1000µF 6.3V cap in the feedback loop.

I was looking at these, but realized I had forgotten to order them... I will make a list of all the remaining caps and order some more. The cost of all those little caps is trivial compared with the big PSU caps I've already replaced.

I was also thinking of bypassing the tone controls and tone amp section, but I'm not certain how to do this properly after studying the schematic.

Thanks.