Author Topic: Yet another LM3886 amp PS question  (Read 1187 times)

PurpleTheory

Yet another LM3886 amp PS question
« on: September 12, 2005, 02:44:41 PM »
Sorry about all the questions about this, thanks again to everyone who helped me out before. Okay, I built the lm3886 amp from ggg
( http://www.generalguitargadgets.com/pdf/ggg_lm3886_amp.pdf )
and built ggg's 18v bipolar ps to power it
( http://www.generalguitargadgets.com/pdf/ggg_bipolar_ps.pdf )
Finally got it working, but volume level is very low, similar to that of a ruby/little gem. The transformer that I was using was 24v 1A. It was suggested that I try a different approach to the ps with a bigger transformer like this:
http://www.interaccess.org/arg/arg-list/binoqdIgJ1Ae7.bin
So I think that's what I'm going to try and build, but I just had a couple of questions before I start:
I already have a transformer that is 36vct, and I'll have to double check, but I believe that it is 2.5A. If I were to use this, which diodes should I use for the rectifier bridge and also how big of caps should I use. My other concern was, will I have to replace anything in the actual amp circuit, all my caps are rated for 50V, but I wasn't sure about the resistors (all 1/4w) will those be all right? And also, I wasn't quite sure about what kind of fuse to use.

Thanks for all the help,
Matt

Johan

Yet another LM3886 amp PS question
« Reply #1 on: September 12, 2005, 02:50:44 PM »
what kind of signal are you feeding it with?. the gain is set for a linelevel input, if you feed it with only guitar, you wount get much volume at all. try it with some kind of preamp/booster between guitar and amp.

johan
DON'T PANIC

Johan

Yet another LM3886 amp PS question
« Reply #2 on: September 12, 2005, 02:54:58 PM »
or increase R1 to 100-200k

johan
DON'T PANIC

PurpleTheory

Yet another LM3886 amp PS question
« Reply #3 on: September 18, 2005, 02:42:31 PM »
I tried it with my bsiab in front of it and it makes it a ton louder, but I still don't think that it's nearly as loud as it could be. I'm going to try switching out R1 aslo as suggested. I think I'm going to build a more powerful PS too. I have a 36V 1.5A (i think) transformer that I want to use. I brought the schematic posted earlier ( http://www.interaccess.org/arg/arg-list/binoqdIgJ1Ae7.bin ) to a local electronics store, and a guy there said that I would lose quite a bit of voltage from the diodes and suggested that I use 2 bridge rectifiers instead and that I would end up with around +-24V, the guy seemed pretty knowlegable. I plan on putting an in-line fuse to the transformer, but I was wondering what kind of fuse to use. I have a few 3A 250V fast acting fuses, will that work? Also, will an unregulated PS pose many problems? I have some 3300uF caps that I was going to use to filter the PS, will 2 of those provide enough filtering?

Thanks,
Matt