47uf vs. 100uf-470uf power supply filtering.

[lowend]

I put a voltmeter on it and it's 9.2V with no load. Does that mean it's regulated? It's 1A capable switching style. I posted all about it on the valvecaster thread , you're welcome to check that out too.

That schematic of the valvecaster is more or less what I'm building right enough. 12AU7 valve heater specs are 6.3V @ 300mA in parallel or 150mA at 12.6V in series. I'm dropping in resistance to get the 6.3 to the heaters from 9V. So 300mA + whatever the rest of the valve etc draws off the 9V.

Big arse capacitor huh? I'm all ears. What does the power supply rating have to do with it? I wasn't under the impression that the cap itself sucked any power.

[Mark Hammer]

Okay, here's a question to which I do not know the answer, but others might.

Batteries vary in their instantaneous current-delivery capabilities, right?  Would it ever be the case that a stompbox needs an instantaneous current delivery that exceeds what the typical 9v battery can deliver, and if it did would it:
a) be something that a larger PS cap to ground could offset (by storing up current)?, or
b) likely be the sort of pedal you'd never want to use with a battery anyways.

[merlinb]

That schematic of the valvecaster is more or less what I'm building right enough. 12AU7 valve heater specs are 6.3V @ 300mA in parallel or 150mA at 12.6V in series. I'm dropping in resistance to get the 6.3 to the heaters from 9V. So 300mA + whatever the rest of the valve etc draws off the 9V.

Ah, the original valvecaster has the heaters wired for 12V, but runs them from 9V, so there is less current drain.

Big arse capacitor huh? I'm all ears. What does the power supply rating have to do with it? I wasn't under the impression that the cap itself sucked any power.

With an unregulated PSU all you have is a transformer, rectifier and reservoir cap (inside the wall wart). If you add another cap in the pedal itself then that basically just adds to the total reservoir capacitance. The bigger the reservoir the more ripple current there is in the rectifier and transformer, and that puts strain on them, which is why you would want the PSU to have a current rating at least twice the DC load current.

You don't get this problem with an RC filter because the resistor isolates the rectifier from all the extra capacitance.

[merlinb]

Batteries vary in their instantaneous current-delivery capabilities, right?  

AFAIK, the internal resistance of a new battery is a fraction of an ohm, less than the ESR of an electrolytic capacitor! In any case, pedals run on milliamps, there are never any heavy current transients to worry about.