[Juuso]

Caps C7 and C10 seem to be part of PSU. Does "more capacitance is better" apply here? I have a few 5600uF caps in hand and a couple of them would fit nicely in the place of batteries on board, since I have Bugle PSU in use.
 

[poty]

The caps are more like bypass, they are on the signal path, so it's better to have more quality than more value (IMHO). In my opinion - changing the caps (or removing them completely and alter the C8, C11) to good film capacitors in the range of 10uF will be best sounding solution.

[Juuso]

C7 and C10 are on the signal path? Are we really talking about the same caps; the ones inbetween battery and power switch, on the lines providing voltage to opamps?
Yes, the ones parallel to C8 and C11... Yes, I'm confused now.
The only caps on the signal path I thought were C1 & C4.

[poty]

Yes, it's unbelievable, but power supply is the half of the circuit where the signal currents flow (the other half is the active circuit itself, which is equivalent of input signal controlled resistance in serial with the output). Usual power supply resistance for sound frequencies is not sufficiently small, which led to signal dependent fluctuation of current. To achieve better behaviour the power sources are usually bypassed by capacitors big enough to behave as short-circuited for the given output in the sound band. The term "big enough" poses some uncertainties in some situations, where you need big values, which don't exist in film capacitors (and expensive too). In the case you can use electrolytics (which can't usually cover high frequencies by design) bypassed by small value films (not enough value to cover low-frequencies).

[Juuso]

Yes, it's unbelievable, but power supply is the half of the circuit where the signal currents flow (the other half is the active circuit itself, which is equivalent of input signal controlled resistance in serial with the output).

I don't have experience on RIAAs, but still we're talking here about feeding OpAmp with a current enabling it to enhance the signal passing thru it: I fail to understand why the signal would be affected by capacitance on PSU side feeding the OpAmp except in regard to having enough filtering to make the voltage stabile. This was the logic I had inbehind of thinking "the more the better". Now I'm just puzzled.

[poty]

It's not specific to RIAA. Almost every circuit uses this particular technique to minimize bad things of non-ideal energy supplies.
In this case: if we look into the datasheet we can see that the Quiescent Current is about 4 mA per amplifier (in one IC case there are two amplifiers). Quiescent Current is a current which powers only internal circuits. The amplifier could put up to 35 mA (each) to the output, the current comes from the power supply rails. As soon as the output current should change according to the input signal (the purpose of the amplifier), the changes are propagated to the power rails and the power supply should be able to supply the current with the speed of changes (frequence of the signal now amplifying). So the last capacitors should be able to do that. Most electrolytic capacitors are ineffective at the frequencies more than 8-10kHz (and the more the value of the capacitance - the lower frequency the capacitor can support), so, to achieve the goal of supplying high-frequence part of current, you have to use some film capacitors. As you can see - your paradigm about "more capacitance - better" is not right if we speak about bypass capacitors, it is more for filtering capacitors inside the power supply itself.

[Juuso]

Thanks for the reply - again.
What I originally understood as bypass caps working as per you write, in this case, to be C8 & C11 only. And they would be bypassing C7 & C10. And C7 & C10 I thought were part of PSU, and therefore I thought more capacity to be better - having C8 & C11 in place for bypassing them.
Thus, I understand "more the better" to be fine for PSU, and also that bypassing caps better to be small films. What I've been failing to understand is that C7 & C10 are not to be considered as part of PSU here, but also having bypass function in this circuit. Ok.

Hmm.. I do have those spare 5600uF caps... And Bugle should get as good power as possible... Would it be beneficial to solder a couple of these caps inbetween Bugle PSU and Bugle? I.e. in front of C7 & C10 (and keeping C7&C10 as per spec) and thus in principle on PSU side? Or is there again something I'm missing here also?

[poty]

You can easily use them in the power supply itself (if you use Bugle PS schematic) in, for example, C3, C6 position. If you are going to use something else - you can try to use a kind of decoupling circuit: 5-10Ohm serial, your caps, 5-10Ohm serial (like R2, C2 in the Bugle PS), but I doubt you'll hear any improvement.
And maybe you took me wrong: I'm not against using different (and more value) caps in the C7 & C10 positions, it can be so your capacitors are better quality than specified, my idea was that you should choose capacitors not only by their capacitance, but other specifications too.

[hagtech]

poty is right - more is not always better.  Sometimes quality is more important than the number of microfarads.  You'll see a lot of manufacturers making this mistake.

jh