DIY Randall rg 100 "preamp from hell"

[phatt]

Looks like they are 12VDC at 12Amps. plenty of current
Not sure about using them stacked in series for double the Voltage but obviously it's working for you.

You may find dirt cheap computer power packs at your local recycle dump shop or Salvo's and other op shops. I've picked up several switch mode power units at my local recycle outlet.
I Picked up one this week for $2. 9VDC at 2Amps,,,just needed a mains lead.
Perfect as I was wanting a spare power unit for my pedals but it does have a noise issue,, (read more below)

I've found it's a lottery when using S-mode supplies for Audio as most are real noise makers. :grr :trouble These use High speed switching circuits and introduce a lot of RF noise which requires a fair bit of filtering otherwise that high pitched whine ends up coming through you speaker.

I ran into a problem a while back while trying to plug my korg Keyboard into a big PA system. The Keyboard is powered by a switchmode unit and although the hi freq whine is barely audible through the keyboards on-board speakers once you DI the line out to a full bandwidth,,i.e. 1,000 Watt PA the hi frequency whine is clearly heard. Needless to say I was very pissed off as it stuffed up my whole gig that day. :grr

I've recently been looking into how to circumvent this problem in future and found good advice here; http://ka7oei.blogspot.com.au/2014/08/completely-containing-switching-power.html

This chap explains the problem very well and shows how to make your dirty switching power supply clean. <3) <3) <3)  I'm experimenting with some of those ideas right now to see how well it cleans up and so far I've cleaned up the high freq whine,,, just need to work out how to install it all in a neat tidy box. If it all works out I'll post the results. :tu:

Getting back to your Q4/ regarding a low wattage power amp chip,, Easy to get 10Watts from an LM1875 and I think they may even run on a single supply. Others here may have even better options for you to explore.
Phil.

[Charliegriffin]

I'll  check around my local recycling salvage next time I take my trash that way (I usually use the dump nearer my work which doesn't take any electronics) see what I can find. Thanks for that link that's a very interesting read and a useful couple of curcuit definately bookmark material there. If I mimic the process that guy took with a couple steps I could potentially turn what I have into a more permanent solution. My original intent was to salvage or buy a 24v or higher transformer eventually and build a power supply for it but maybe I'll skip that step.
That lm1875 looks like the best option I've looked at so far I'll probably tack a few on to my next order to experiment with.
After looking overy my breadboard I found a couple capacitors that were way off replacing them cut actually quite a bit of the higher pitch whine and even some buzz. as long as there is notes coming through the speaker it sounds good just the silence isn't totally silent
I also tried running it using 2 9v batteries connected in series to make 18v it had about the same amount or buzziness either way I don't know if that means much. If I put my hand pretty close over the curcuit I can cut the static-y kind of hissy bits of the noise down to where it's a pretty dull even hum I assume that's basically a preview of what I can expect to change when it's mounted in a grounded chassis? I don't know maybe not
Another thing I'm starting to wonder is how much noise is coming from my cheap (and pretty far from new) cables or the amp I'm hooking up to or even my guitar that my be the next test I make.
Anyway thanks for the help and interest I'll come back with any updates