[sapphiremodena]

Please someone tell me about the Barebone Amp!
It's basically a version of the Cmoy amp with only the bare necessities. It supposedly sounds the same , is this true?
And just how small can it be? How much does it cost?

ANY information you have on the Barebone Amp would certainly help cure my curiousity.

 

[Possum]

I thought the cmoy was an amp with almost the bare necessities to begin with. This weekend I put together another cmoy following only the first schematic you see on the project page, and that pretty much is only what you need. To furthur reduce the number of parts needed: 1) you could just forget about the LED for the power-on indicator, 2) if you can find a headphone jack that has a switch (normally open when nothing is plugged in, closed when something is plugged in), you could get rid of a separate power switch, 3) experiment with R5 (I believe this it's R5 anyway, the resistor between the op amp output and the feedback loop or headphone output) to see if you really need it to lower or get rid of noise (read about it in the project article).

If you place the components tightly on a board in the right way, you can get the plain cmoy to fit in 1 square inch of space (including the power supply portion) at about the height of your tallest capacitors +2-3 mm. Then you just have wires sticking out for the jacks, potentiometer, battery clip, LED, and power toggle switch.

 

[grrr223]

ooh, this could be a fun contest:

How small can you make your headphone amp?

This is a very uneducated suggestion, I haven't thought about it at all, but could you put one of these amps in an audio cassette case? I think it would be cool to be able to see through to all the compents inside? although I guess they're not that sturdy are they

, oh well, worth a shot.

 

[Possum]

In the old HeadWize forums, someone made an amp inside of a rechargeable 9V battery case, so he would just hook up another 9v to the ends (so it would look like two 9V connected to each other). Of course the assembled circuit looked like heck, but it's about the miniturization

 

[grrr223]

Wow, that is so cool, aren't there a lot of bad things involved in taking apart a battery though?

 

[Possum]

It was a 9V rechargeable battery case - it was basically just a plastic box shell that some rechargeable battery pack would go into.

 

[chych]

You mean, Skippy's amp?

 

[skippy]

i originally planned to put it into a plastic 9v case, but then i decided to use a metal 9v duracell case. i've actually built anther one of these into a metal panasonic 9v battery case (i'll post pictures when my brother returns my digital camera). this time the layout is much cleaner and much smaller. it went much better the second time around. i think i can get enough room to build another battery sized amp with 2 opamps in parallel. (that's my next project right after i build some full range driver voigt pipe speakers)

here's a close up of the original battery amp:

 

[Possum]

Woops I had it backwards. The plastic case I remember was just his power source

 

[Apheared]

Quote:

that's my next project right after i build some full range driver voigt pipe speakers

Go skip.. Are you a fan of TQWT designs or Paul Voigt's ideas? Not that headphones are full range drivers, no that's not it at all... heh... I just figured you more for the loaded horn type.

Anyway, aren't we done with the subminiature silliness? Skip's battery was bad enough, but who was it? Kevin? etched out a board with a tiny chip and an inverter with like the boardspace of your thumbnail? Building em small isn't the problem, POWERING THEM is the problem... whether you sit there all day with a loupe stuck to your eye workin SOT-23 or just use good ole DIPs, your amp will still be smaller than a 9V battery if you want it to. jacks, pots, and LEDs optional.

What's the point? Is there a contest /slash/ race I'm not aware of?

 

[cmoy]

If anyone else builds "barebones amp," please post pics!!! I love seeing these miniatures. Here are some ideas:

pendant amps (basically attach a neck rope)
headphone with built-in amp
armband amps (amps attached to an armband)
hat amps (amps built into hats? )

 

[skippy]

i just found some of those discontinued 1354 full range rat shack drivers. neruda pointed me out to some full range driver and tqwt sites, and i've always been curious about that kind of stuff. what kind of speakers do you have?

i think it was benny jorgensen who made that insanely small amp. for me, it's just a pain in the ass to carry around a huge amp (and there's alos a bit of novelty to having an amp in a battery case). the the ones that i've made so far were for high impedance cans, but i use grados on the road. which is the reason for the next amp with a parallel output. but do agree with you that it's the batteries that are the real culprit. the batteries are what take up the most space, especially if you want to power them correctly.

 

[grrr223]

I still don't understand how you got a case to a battery? I would love to build of those, to just have 2 batteries with some wires coming out of them would be a lot cooler looking than having a seperate portable amp. Hmmm, the TA doesn't look very small after seeing that

 

[skippy]

i took a dead battery, and unrolled the lip on the bottom. i pulled out the cells, and viola... a nice small case to use.

 

[grrr223]

oh awesome, so it doesn't involve getting into a bunch of toxic chemicals?