lm386 power amp louder

[fiend138]

hi is there anyway i could make the lm386 amp from GGG six times louder?

Max

[R.G.]

Each doubling of apparent loudness needs ten times the amplifier power, all other things being equal. So you're asking for two doublings and about 50% more than that?

That's about 400 times the power. Just the power supply for that kind of amp is a major (and expensive) project.

Did you mean the LM3886 project? I couldn't find a project on the LM386. The LM3886 is already a substantial amplifier.

[fiend138]

the bass player in my band needs a new power amp, and he'd like it to be around 400 watts if possible. I was just checking to see if it was possible to do this with a lm3886

[R.G.]

OK, that's a bit more straightforward.

First: no you can't make a 400W amp with an LM3886. You might be able to do it with eight of them.

Second: the power supply for such an amp is big and expensive. A power amp is best thought of as primarily a big power supply with some other almost inconsequential junk to let some of the power out to the speakers under carefully controlled circumstances.

The LM3886 can supply about +/- 35V peak to a speaker. Any more raw power supply will fry the chip. Two LM3886's in bridged mode can supply +/-70V (about) to a speaker. But they still have to live within their current limitations. You need about four of them in bridged-parallel to supply 200W and that's into 4 ohms. You *might* be able to double the number of devices and get to 400W into two ohms. If he's only using one speaker at 400W/8 ohms, the 3886 won't get you there. If he's using four speakers, it makes sense to make four 100W power amps and drive each speaker separately. It's less failure prone and simpler to build four low power amps than one goliath.

National Semiconductor has an application note describing bridge-parallel connections of the LM3886.

You should look into the TDA7293 as well. It's in the same package as the LM3886, about $1.00 more expensive per unit, but it has provisions for paralleling built in. The LM3886 does not.  You'll still need about eight of them to dissipate the waste heat into some big heat sinks.

[fiend138]

would it be possible then to send his preamp through the GGG simple mixer into four lm3886 power amps in to four cabs?

[R.G.]

Yes. Good idea in fact, by my way of thinking. If one amp dies. you don't lose the whole show.

[Mark Hammer]

Second: the power supply for such an amp is big and expensive. A power amp is best thought of as primarily a big power supply with some other almost inconsequential junk to let some of the power out to the speakers under carefully controlled circumstances.

If he's using four speakers, it makes sense to make four 100W power amps and drive each speaker separately. It's less failure prone and simpler to build four low power amps than one goliath.

Eminently sensible in a variety of ways.  First, the sorts of transformers one would need for a 100W amp are generally far more available and reasonably priced than what you'd need for 400W.  I assume part of the motivation for build a power amp would be to save a few bucks.  If one spends $150 on a transformer, and then STILL has to deal with the rest of the costs (chassis, caps, chips, connectors, etc.) and quality assurance, why the hell not buy a used power amp from someone trying to ditch their PA, an old Crown or QSC or Peavey or something.

Second, why does anyone want or need that power?  Well, certainly not for THEMSELVES to hear.  In which case, why stick all the power and speakers in one place?  Why not stick a cab here, a cab there, etc., so the other musicians and other side of the audience can hear?

Third, does a person need ALL that power and ALL those speakers for every occasion, even for practices?  Call me naive, but I don't think so.  Making things modular affords flexibility of setup, and scaling up/down as needs be.  For that matter, you could start with a pair of 100W amps and see where that takes you.