Getting V+, V- DC out of transformer.

[eliktronik]

Hey everyone. I ripped apart and old 10w amp with plans to create a better sounding amp in its place. After messing around w/ lm386 ckt's I decided that I want to use the original amplifier (tda2030a) after a lm386 ckt to get a decent amount of power and good tone. Anyway, I found a link for an 8w amp, and I need to have a V+/V- DC supply. The amp originally had a transformer w/ a center tapped secondary (i think that's what it's called). Is there a way to get +/- DC from that using only one full wave rectifier? I believe that's how it was done originally, but I killed the circuit board and can't tell exactly. Can anyone help? Btw, the secondary produces 24v across the 2 wires, with a white wire that is 12v rel to either of the other wires (center tap?).

Oh, and here's the link to the amp schem:
http://www.mitedu.freeserve.co.uk/Circuits/Audio/tda8.htm

Anyone think this'll work as amplifying the output of something like the Little Gem? Maybe i'll just use it to amplify a tube pedal like the shaka tube... I guess I'll have to build both and compare.

Thanks to everyone on this forum for all the help I've gotten so far.

[brett]

Hi.  This sounds fairly simple.  If you've got a wire that 12V wrt the others, it's gunna be the centre tap, which you use as the "earth".  The others are giving 12VAC, which you can convert to DC via a bridge rectifier and a couple of chunky (large value) capacitors.  Common, single-component bridge rectifiers (W04?) have two connections marked "~" and a "+" and a "-".  Connect the AC transformer wires (not the centre tap) to the "~" (either way around is ok).  What you'll get out of the "+" is +DC (with lots of residual humpr "ripple") and -DC out of the "-".  To "smooth" the DC lines you'll need to connect large electrolytic capacitors (a couple of thousand uF at least) between the DC supply lines and ground.

Have a look around the web and I'm sure you'll find something similar to what I've described.

Good luck!

[eliktronik]

Thanks Brett. That's what I was thinking but was unsure whether the center tap would serve as a ground without doing anything to it... I guess it will.