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Discussion Starter #1
I bought one of those little Danelectro Hodad battery-powered amps off a fellow on Kijiji a year or two ago, for $25. It's a cute little thing, with a pair of 3" speakers, powered by a 1W chip (though I suspect it's more like 600mw) a headphone jack, a distortion option, plus "echo" and tremolo whose speed can be adjusted by a little accessible trimmer. You can see a reasonable demo below.

I got curious about it the other day and decided to explore the innards. Much as expected, it was a hybrid of surface mount and thru-hole, and used the ubiquitous PT2399 digital delay chip for echo. The "echo" is simply a very short delay with fixed level and repeats/feedback. It will take me a bit to see where on the board those parameters are set, but I *did* see that it used a fairly textbook arrangement to set delay time - a 6k8 resistor to ground from pin 6. I sweated out the teensy 6k8 resistor, and installed a 50k pot in series with a 4k7 resistor. Much to my delight, I am now able to get echoes in the old Memory Man range (around 400-450msec). I could have gone higher, but, not knowing whether the filtering would be successful in keeping the audio grime out, I left it at a modest max delay time. The portion of the tremolo circuit that I was able to make out looks very familiar, and similar to a rather classic design found on many older solid-state amps. Hopefully, I'll be able to add on a tremolo-depth option. I may also be able to add a second power-amp section to goose the output level a bit.

Not like I was hurting for delays, but being able to have overdrive, tremolo, and real echoes out of a 9v-battery-powered portable amp is kinda neat. Feels like a brand new amp.

 

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Nice.

I have one of the Blackstar Fly 3 amps runs on six AAs. I kinda like it for just sitting on the couch and find myself wondering if they have a bigger amp that sounds the same.
 

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Discussion Starter #3
A sextet of AAs is much better than a 9V. Eight is even better. When we did our cross-Canada trip in 2004, I made myself a 2W battery-powered amp, that uses an octet of C-cells, and powers a 6" Marsland speaker in a decent-sized chipboard cabinet. I wanted something I wouldn't feel bad about losing or breaking. That sucker is pretty loud with a great bass response. Clearly not one of those Yamaha TH things, or a Boss Katana, but as campfire amps go, more than good enough. For a long time, it was my bench amp for testing pedals.
 

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I picked up one of the Roland Microamps a few years ago. It is my "go to" around the house - especially by the pool. Years ago I had a Fender Amp Can that I actually mic'ed up and did a gig with. Those little guys can be a heap of fun.
 

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The real little ones small enough to use as a slide while plugged in can give some great feedback. :D
 
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