little portable amp

[hardi_ami]

Hello !
I'm looking forward to building a really small low-wattage amp running on batteries so that I can play at friends or on the beach without moving my big amp. I've thought about the Marshall MS-2 which has a schematic on the site, but maybe someone knows a better or alternative one ? I don't really need 2 channels .. the overdrive is enough

Thanks!
Michael

[Joep]

Check the Little Gem at RunOffGroove.

[hardi_ami]

Thanks !!
This circuit seems very nice and cheap I'll try to build it
Would you know what kind of (cheap) speaker would sound good with it ?


Michael

[Peter Snowberg]

I built my first LM386 amp back in High School in 1987 using the 3 inch speaker that came with speech synthesizer and the monitor circuit from a 2400bps modem. With a 9V battery, 1/4" input jack and 1/8" output jack (for headphones too), it all fit in a Shure stylus case (like a ring box) and worked great. I am still very satisfied the circuit which is just about identical to the Little Gem.

A couple years back I tried it out with a 10 inch speaker.... WHOA!!!!! It sounded GREAT with a big speaker! I plugged it into my Fender Twin 2x12 and it sounded even better! $400 worth of speakers and $1 worth of amplifier.  :shock:    :wink:

I would get a cheap 10 inch speaker to really get the bass. I have tried speakers ranging from the 3/8 inch unit in a cell phone, to all sorts of various small speakers, 3 inch, 4 inch, 6 inch, 6x9, 8 inch, 10 inch and 12 inch. 8 inches is as small as I would go for an open back enclosure. Close things up any it's a whole different story I'm sure.

If you want low volume overdrive, I'm sure you will be VERY happy.

-Peter

[hardi_ami]

wow thanks for your answer
a low vol. overdrive that can be moved easily .. yeah that's what I'm looking for. 10" seems a bit ... big for what I've imagined, I think I'll stick to 8" or such !
thanks again

michael

[Gary]

Try to find a speaker with a high sensitivity rating.  Guitar speakers are the best, but you may find a small and cheap speaker with a good enough sensitivity to give you the best volume and sound.  By all means, do try plugging that circuit into a guitar cab for the "giant killer" effect that Peter mentioned.  You won't believe it's only a little half watt chip driving your speakers and sounding that good.

[JasonG]

I built a portable amp out of an old Fisher price record player. I works grate, is loud and has nice distortion. The only changes I made were putting in bigger caps and getting ride of a the resistor in the input stage that was needed with a record needle but not with a guitar and a 9v clip and I was ready to go  an hour. I use my guitar volume for volume I took out the volume pot in it and shorted the connections. I also wired it to turn on when I plug my guitar in.

[hardi_ami]

thanks for all your answers !!
for now I intend to buy a small cheap (not guitar) speaker, so I'd like to know, what should the frequency bandwith approximately be ? I've seen big celestion with something like 70Hz-5kHz with a peak at 100Hz .. but 5kHz seems quite low ...
Anyway, I'll remember to find some high sensitivity speakers ...

Michael