Battery 386 Guitar Amp

[anickode]

Hello all! This is the second little 386 amp I've built... The first one worked ok. The board was a little messy because my soldering iron needed a new tip and I sorta threw the thing together really quick. I put a little more time into this one... Currently working on a small cabinet with a single 10" 8 ohm full range speaker.

Here's the amp.

[Rembrant]

You intend you power a 10" speaker with 300-400mW? You might want to look into something that has maybe around 10W. I have several amps made from this chip for headphones and for small portable speakers. I like them, I just don't think it's going to have the guts to drive a 10" full range speaker.

[Andrew Eckhardt]

Yeah I think you'd want to stick with a real 10" guitar speaker since you might get another 10dB of efficiency there (unless you already know what you are doing for sound reasons), and probably a bigger switching amp.

[anickode]

I've played through this amp hooked up to the speaker I'm using, and it's surprisingly loud. Installing it in the cabinet should give it a bit of a boost too. The great thing about guitars is it doesn't take much power to get a surprising amount of sound. A 10 watt amp is more than enough to really **** people off. This isn't supposed to be a gig amp or anything.

The point of this amp is something small that you can easily carry in a backpack around campus or something, and have good battery life so it can just be taken out and jammed on for a while. A 10 watt amp would be more power than necessary, which results in needing a large battery pack (as opposed to the 8 AA batteries I'm using) to sustain the power for extended times.

[Andrew Eckhardt]

All that's cool, of course. What I'm talking about is something that could be played maybe 5 times longer on the same battery.

[anickode]

Hmm well perhaps that might have to be the next little projects. Do you have schematics for it, or is it from a kit?

[Andrew Eckhardt]

Look on Digikey for the low power class D ICs. You can follow the application circuits provided in the datasheets. A problem is these devices are being developed for absolute minimum board space and some of them can't even be handled by typical experiementers. You'd think someday soon some kind fellow would get into the business of selling parts like this on DIP headers for the hobby builder. The other half of the efficiency improvement depends on the speaker itself. A lot of 10" full range drivers might be well over 90dB 1W/1m, but not many hit 100dB though much of the band, as you might find with a guitar specific driver. You could probably have higher efficiency at lower frequencies with a regular 12" driver. A fully tweaked out design would take some research. Check the range of guitar speakers at eminence.com for an idea of how various 10 and 12 guitar speaker compare to your driver. They even have sound clips posted for some. The Liltexas and Tonkerlite 1/4 pound neo magnet 12s would be an intersting angle on a minimum weight, maximum sound kind of thing, although who knows whether the tone would agree with you, with our without a tone stack. The acoustinator series of 8" neo drivers for acoustic guitar would give you gobs of bottom and flat response compared to the usual guiter speaker, but the lower resonant point and smaller size deals some hits to overall efficiency. They have some 10" neos for bass. Dig in.