Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Amplifier Discussion => Topic started by: Stompin_Tom on August 16, 2006, 04:49:57 PM

Title: ok... one more stupid transformer question..
Post by: Stompin_Tom on August 16, 2006, 04:49:57 PM
Sorry about this everyone... I'm just knew to this world of ac. I'm (still) planning on putting together a stereo guitar amp based on the stereo lm3886 kit from chipamp (not the dual mono, but with one power supply). I'm hoping to get this kit for my b-day in a week and I'm planning ahead for what I'll have to buy. So, I'm looking at this transformer that RDV recommended:

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=122-615

RG said this would be good to power two lm3886, which is what I want to do... but, now here's where the stupid question comes in, it has 22v + 22v secondaries... does that mean it has four secondaries of two pairs of 22v (each pair with a + and a -)? ...and ground. If I understand the schemo from the kit that's what I'd need, correct?

Also, unrelated question, if I'm planning to push 8ohm speakers I'd probably want something closer to 35v to get 50watts output, correct? Got that idea from the datasheet (http://www.national.com/pf/LM/LM3886.html).
Title: Re: ok... one more stupid transformer question..
Post by: teemuk on August 16, 2006, 06:02:05 PM
The transformer has two 22 V (RMS) secondaries. Depending of how you connect the secondary it can either provide 2 x +22 V, 2 x -22 V, 1 x +44 V, 1 x -44 V or + and -22 V. Ground is where you decide it to be. Peak for 22V RMS is about 31,11 V so you could expect +- 30 VDC under no load condition. Seems ok.
Title: Re: ok... one more stupid transformer question..
Post by: Stompin_Tom on August 17, 2006, 10:37:39 AM
Yes, actually, clears it up for me. Thanks!