[arspy87]

Hey guys,

Just figured I'd post pics of my first amp, it's only a CMoy but I had a great time making it, and it sounds surprisingly really great! I'm using my laptop as a source and either Grado SR225s or AKG K240s. I was surprised how much the bass response has improved, and also how it really quiets the noise floor typically coming from my laptop.

I followed the typical design, except I used 0.22uF caps for input filtering instead of the standard 0.1uF, and I used a 100ohm resistor on the output (outside the feedback loop) to quiet any output noise, and also to compensate for the fact that I'm using the CMoy with relatively low impedance headphones. Op amp was the standard Burr-Brown OPA134PA-ND.

Pics:

Showcase of the world's worst soldering ever:

Innards!

Finished product (yay):

Comments, recommendations, and insults at my soldering skills are welcome

 

[Ace o' Spades]

Insults? Nah. Great job, looks a tenfold better than my first cmoy.

 

[feh1325]

love the casing

nice job!

 

[mminutel]

man, that is sweet. I am just now getting started on mine, the parts arent here yet. I am going to get the board tomorrow and the can. I am glad you posted this because I was wondering if an altoids can would work. Looks like it works like a charm. I am also glad that I see that you only used one battery. The one i saw had two in it but it didnt say how to go about using both. Looks really nice man, I hope mine turns out just like it.

-EDIT- also, could you tell me what type of wire is suitable for this job? i do not see it listed on the parts list. Is it from Radioshack or did you buy it from mouser or another store like that. I want this to work and am just trying to get the kinks worked out

 

[fortney]

Very neat and attractive job. My wife just gave me (an empty) box like yours.

The CMoy is a really good amp. I modified mine a slight bit more than yours and am very satisfied with it.

Uncomplicated amps like CMoy's are fun to set up on plugboard and change or add parts, values, gain, etc. I usually set up one channel this way because I bought a small plugboard. And maybe I like monaural!

F

 

[arspy87]

Quote:

Originally Posted by mminutel /img/forum/go_quote.gif man, that is sweet. I am just now getting started on mine, the parts arent here yet. I am going to get the board tomorrow and the can. I am glad you posted this because I was wondering if an altoids can would work. Looks like it works like a charm. I am also glad that I see that you only used one battery. The one i saw had two in it but it didnt say how to go about using both. Looks really nice man, I hope mine turns out just like it. -EDIT- also, could you tell me what type of wire is suitable for this job? i do not see it listed on the parts list. Is it from Radioshack or did you buy it from mouser or another store like that. I want this to work and am just trying to get the kinks worked out

Yeah the Altoids can worked really great. As far as using two batteries, I think all you need to do is wire them so that the virtual ground is between the two batteries (so they're basically wired in series but with the ground in the middle). It seems to work great with just one battery though.

I used 22AWG stranded copper wire from Radioshack (think it's just called "hook-up wire" or something like that)... it's probably a bit thicker than you'd need actually - I'm guessing 24AWG would work fine too. Good luck!

 

[arspy87]

Quote:

Originally Posted by arspy87 /img/forum/go_quote.gif As far as using two batteries, I think all you need to do is wire them so that the virtual ground is between the two batteries (so they're basically wired in series but with the ground in the middle).

Forgot something - I think you get rid of the two power resisitors too, since if your ground is between the two batteries you already have your +/- voltage split across the op amp.

 

[Paragon]

Quote:

Originally Posted by arspy87 /img/forum/go_quote.gif Forgot something - I think you get rid of the two power resisitors too, since if your ground is between the two batteries you already have your +/- voltage split across the op amp.

That is right for the simplest virtual ground with 2 batteries. The connection between the batteries (+ & -) is the virtual ground and the other + & - is the new voltage feeds. You can still use a voltage splitter if you find you have issues with the voltages being biased to + or - a lot.

Use stranded wire for chassis stuff (wiring switches, pots, etc.) and either can be used for jumpers on boards. Sometimes it is easier to use solid for jumpers as you can shape them and they stay where you want (you can even use the excess wire cut from resistor leads for quick jumpers or keep them attached and route where you need)

22AWG or smaller should be fine. Some wire has thicker insualtion than others but I think it is the equipment wire/test lead stuff from ratshack.
Most resistor leads are 22AWG or even something like 26AWG for really low wattage stuff.