I have been building a mystery box. I used schematics from someone called 'carlosfm', and a soft-start (to try and prevent the toroid inrush current from blowing fuses / dimming lights) from Rod Elliot, and drew up some home made PCB's.
It's a two channel amplifier based on LM3886 chips, ~38WPC in to 8ohms and ~80WPC in to 4 ohms (I think, I forget... watts are over rated). Each channel has it's own regulated power supply, sitting on a 500VA toroidal transformer. Speakon sockets for the speaker outputs, RCA for input. Considering switching to XLR for input, not sure yet
2U rackmount case from Maplin, they sent me a used one at first and I had to wait a whole week for replacement! Urgh!
I measured the speakon's as 25mm, so got a 25mm holesaw... and the hole is too big, you can see the hole edge on one side I am going to try and fix this with some rubber edging if possible though. Also couldn't be bothered drilling a hole for the power LED
My camera seems b0rked sadly, so no pictures of inside yet. I might not want to show you all how bodged up it is anyway To insulate the bottom of the PCB's from the case they're currently bolted to badly cut and drilled wood, which I might well replace with some sort of plastic or perspex / plexi. I think this would look alot nicer. The screw holes on the PCB's are actually all over the place too, but it all works... and I have learnt from all these mistakes of course (considering redoing the actual amplifier PCB's with slightly updated PCB's, but this would mean redundant screw holes in the bottom of the case. Whoops.) and it sounds just as loud as my current commercial 60WPC amp (which I am also using as a pre-amp for this amp now aswell). No thump on turn off or on, no audible humming, I am not really an so called "audiophile", so I won't even try and go in to all that audiophile talk, but it sounds just as good as the commercial amp (which is nothing particularly special mind) I can say that much Can't hear any distortion even at full volume, which is nice.
The finished(ish) product
Early version of an amp PCB
A freshly etched and drilled PCB (i've since discovered Eagle can fill in blank unused space automatically to reduce etching time quite and allow more use out of the etchant!)
Early single channel running on my bed (probably quite dangerously) to test it out
The best part is that now I've finished it I don't know what to do with the dang thing! Do I trust my bodge work enough to use it?
Cost far too much to build probably about £130, but a fair amount of that was "one time" sort of stuff, like etching stuff and things. I think it should "only" cost me about £70 if I were to build another now. More money than sense perhaps. It has been quite a learning experience though I suppose
EDIT: dunno what's going on with pictures. Seems you have to click them to see them now?
Edited by markiemrboo, 02 December 2006 - 08:20 AM.