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Old 19th January 2006, 12:25 AM   #1
diyAudio Member
Join Date: Sep 2003
Location: Illinois
Default LM3886 Bridged Amp


I haven't been around here lately, have been pretty busy and haven't had a chance to work on any electronics.

Anyway, I'm about to start on my best project to date - a 4xLM3886 (2 per channel) bridged stereo amplifier.

I've already got the case built, and the transformer, and am just about to start building the amp.

My plan is to use a 26-0-26 350-400VA transformer that supplies roughly +/-35VDC. The amplifier will use 4 lm3886's in single ended mode, but bridged into 2 channels using a drv134. That means there is a control board with 2 DRV134. I also have an OPA134 opamp for the sub crossover.

I'm planning on running two 8-ohm in-wall speakers with this (can't remember brand off the top of my head). They're currently powered by my Stereo LM3875 amplifier, but it just doesn't have enough power and is showing clear signs of stress, such as odd distortion sounds and a LOT of heat dissipation.

Does my plan sound like it will work? if so, I'll be making the PCBs tomorrow!
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Old 20th January 2006, 01:36 PM   #2
diyAudio Member
Join Date: Sep 2005
Location: Melbourne Florida
Default LM3886 Bridged Amp

Power Supply voltage is a little high, If you are cutting youre present amp into thermal and spik protection it will be worse in a bridge config
when the chips are bridged they will see half the individual load so if you are driving 8 ohm speakers each amp will see 4 ohms instead of 8 effectivly doubling your power dissipation. To use a bridge config I would drop the supply to about +/- 22V DC should get you about a 100w or so, Or try a parellel solution or a bridge parellel one.
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