Very silly capacitor question...

[EFK]

Does size matter? I don't mean this in terms of actual flltering ability or cap quality, but rather, the simplistic explanation I see here or there comparing a capacitor to a battery bank. I'm looking at the question in terms of power supply sag: often a cap is referred to as a "battery." OK, so if this is the case, under a heavy power draw, would (10) 10 uf caps wired up in parallel for 100 uf be less resistant to discharge and subsequent power supply sag than a single 100 uf cap? Or two 200 uf caps in series compared to a 100 uf? Given that we are comparing comparable capacitances.

On the other hand, what are the implications in terms of charging time; I could look at this both ways, perhaps the capacitor "bank" takes much longer to charge vs. a single cap of the same uF?

[Steve Conner]

What you're talking about goes under the name of "ESR"- Equivalent Series Resistance. For guitar amp circuits it's negligible, and the 10x 10uF caps in parallel, single 100uF cap, and 2x 200uF caps in series all behave exactly the same.

I've built high power circuits where it's not negligible at all. In one I used 6x 470uF, 400V caps in parallel, because that offered better ESR and ESL per dollar than a single 2200 or 3300uF one.

[greekie]

This is actually not a silly question at all in my oppinion!

I once had an old blackface Fender that I had to recap and reverse some heavy mods on. Anyways, when I got it back to it's original shape, it sounded a bit too stiff. Even with the tube rectifier, there was something missing. I tried replacing the new filter caps with the old. Both caps measured the same value +/- 5%, and the old made the sound less stiff!

I added some series resistance to the caps, and that made the circuit sound the same with the new caps.

YMMV.

Jake

[Steve Conner]

Well, OK, this is an important point.

The ESR is supposed to be negligible, but once the caps are 50 years old and dried out, it can get much higher and make a big difference.

The "stiff" way is more how it would have sounded when it left the Fender factory.

[greekie]

Yeah, but we don't like stiff, remember? ;-)

I also tried with smaller value capacitors, but that didn't give the same feel in a way. I must have been biased or drunk... or both!

[EFK]

Hmmmmm. drunk biasing. That sounds like trouble.

[greekie]

Hehe, yeah, don't try that at home!

But to get back on the subject, I made some eyelet boards that I use for power supplies in my amps, and some that I use to replace the power boards in older Fenders and Marshalls. My boards support radial components, as those I can get are cheaper (like 10x less) than most axial types, and their specs are very good indeed! I staple a small bag with the original components inside the chassis, so nothing is lost.

Jake