MFOS Wall wart power supply.

[isak]

Hi guys.

2 questions if I may.
If I'm using 12VAC 400mA wall wart and i wanna power with this power supply 2 or 3 modules rated say...30-50mA for eatch module.
1. Can I use 2 capaditors instead of 6?
2. Assuming the answer to Q 1 is yes, can I use 2 X 2200uF instead of 2 X 3300uF?

Thanks in advance,
Isak E.

[Broadwave]

Hi Isak,

I think you may be pushing it a bit... In theory Ray's PSU would give you +/-12 @ 200ma per rail (using a 400ma TX), and if you use 3 modules at 50ma, for example, that would be 150ma per rail, which doesn't leave much headroom.

I usually calculate what current my modules use and double the result for a PSU - I'd up the wall wart to 600ma, just to be on the safe side.

Obviously the more smoothing capacitors and higher value, the better - I guess it depends what the modules are. If they're just simple "aux" modules then it may be OK, but I wouldn't skimp on smoothing if you're powering VCOs, VCFs etc.

If space permits, why not make your PCB with room for more caps, or (as I did on a project once, where room was tight) make a separate PCB for the caps and connect to the PSU with fly leads.

[isak]

thank you Andy.

actually its for small desktop effects.
there is not so much space inside.
this is why i thought to use smaller caps, cause of the size of the caps.
each desktop module is different, some with dual VCF + LFO i dont really think it comes to 50mA per module, its much less but i always take the higher bid.

size example:



so i'm working on shrinking the power supply to very small board.

thanks again Andy