
How to Build the CMoy Pocket Amplifier (2009) - mindcrime
http://tangentsoft.net/audio/cmoy/
======
moron4hire
Seeing stuff like this makes me realize just how far I've come.

A pocket amplifier was one of the first electronics project I undertook, about
10 years ago. It was "hard", in the sense that I didn't know what I was doing,
I didn't have the necessary dexterity to follow the instructions correctly,
and worst of all, I didn't know enough to know how to evaluate what I was
doing wrong.

About a week ago, I finished up a design of a kit, including firmware, custom
control hardware, and other goodies, for an FM/Weather Band radio that
includes multiple output options, but maintains a very cheap BOM. In short,
I've gone from unable to follow instructions to able to synthesize new work
based on vague requirements.

I still have problems like this in some of my hobbies, but now I know a little
more about myself and I know that "hard" problems often fall into those three
categories: knowledge, skill, evaluation.

And once I realized that is how things work, I realized that was what learning
programming was like for me, 20 years ago. It has helped me become a more
effective tutor.

Turns out, a pocket amp isn't the best "beginner's" electronics project. If I
had to teach someone electronics now, it'd start with "all the ways you can
release the blue genie from an LED, why it happens, and what you can do about
it."

~~~
ZenoArrow
> "all the ways you can release the blue genie from an LED, why it happens,
> and what you can do about it."

???

~~~
toast0
It seems the blue genie is an alternative notion of the magic smoke: At the
electronics factory, they put magic smoke into the IC, if you let it out, you
won't be able to put it back in yourself. (Often there's a puff of smoke when
you destroy an IC, maybe when you put the power input onto the wrong lines, or
12v for a 5v chip, etc)

------
cushychicken
Man, I tried building one of these when I was in high school and didn't know a
damn thing about electronics. No multimeter, no oscilloscope, just a soldering
iron and teenage idiocy. I put it together and (big shocker here) it didn't
work, and I didn't have the vaguest idea of why it didn't, or how to figure
out why it didn't. It pissed me off so much that I threw everything away and
forgot about it.

I should really consider taking a second stab at it now that I have an
engineering degree and a snowball's chance of making it work.

------
dopeboy
Ah, the good old CMoy. Built one of these in 2005 right as I started college.
Didn't know a damn thing about soldering and circuits, just kind of followed
along. Building it was my point of entry into hardware and eventually embedded
systems. It worked (after several hours of debugging) and got the most
interesting looks from my friends.

That was back when I would go to HeadFi everyday and follow the latest news on
headphones and amps. Think I even went to a meetup and met Ray Samuels.

------
kqr2
Although more complicated and expensive, another interesting amplifier project
is the open source O2 amp:

[http://nwavguy.blogspot.com/2011/07/o2-headphone-
amp.html](http://nwavguy.blogspot.com/2011/07/o2-headphone-amp.html)

~~~
thrownaway2424
To me it seems pretty obnoxious that this O2 design has licensing terms. Most
people just freely distribute their schematics and board layouts without a
license. I would say that in the DIY community this "open source" amplifier
would be considered more restrictive than nearly all others.

~~~
tinco
In the audio community it is actually very common for shared source designs to
be patented and/or distributed under non-commercial restrictions. I think this
is because many of the best (known) designers actually build, design and
maintain the devices professionally. This might be unlike general
electronics/software engineers that do not usually make money off their oss
ventures.

------
mhd
Considering how long it took me to get a friggin' Covox Speech Thing (aka.
Sound Source) "clone" working (aaages ago), I think I'll pass. Great workout
for your soldering skills, though.

Can you get Tripath amps this size these days?

~~~
analog31
Perhaps not that brand,but there are lots of little switch mode Audio power
amp boards out there.

------
hatsunearu
Powering a relatively low impedance device like headphones at relatively high
powers with an unbuffered op-amp causes distortion. The CMoy is a classic
example of "bad" electronics design.

------
PaulHoule
I remember seeing this one (Op amp configured with some discrete components)
back in the 1970s -- also you can change it up a little and use it to amplify
very different things.

------
Sephiroth87
It's a really cool device and it sounds amazing, the only problem is that you
can't really bring it with you often, especially around airplanes :(

------
bognition
Cool design, How hard would it be to modify the design so the amp could be
powered by 5V over USB

~~~
cushychicken
Not terribly difficult - IDK the opamp specs off the top of my head but you
would have to find one that was happy working at single polarity off of a 5V
rail. However, it's worth noting that decreasing the voltage kind of defeats
the purpose of this circuit, which is to increase the dynamic range of the
music you're listening to.

------
atilev
Hah I actually had built one of these. So cool to see it up again in HN : )

------
RexRollman
This made me remember that I haven't visited HeadFi in a while.

