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CMOY schematic for stereo opamp????

post #1 of 11
Thread Starter 
I can't seem to find a schematic anywhere for a dual opamp based cmoy.
Could it be that opamps are so different from each other?

Also i was looking for a "understanding" of the cmoy, other than the headwize one.
Like why there are caps in series with the signal.
And why there are resistors on the way to ground...

Is there any way to run a mono pot... cause i can't find stereo versions (dual signal)...

Also can some on link me to understanding the power supply and why its split, and HOW its split? i don't see how it works.

Also i am looking for a way to get 3v to 9V or more, with some circuit, but can't find anything other than ICs that are some how programed... and i cant do that.

Thats right i'm TRYING to build a cmoy...

Oh and i was thinking of putting like trimer pots on some resistors just to see what it changes, that might help me understand somthing... and tune the cmoy?!!?! but then there are 2 channels and i would have to match the resistance for each channel, and i dont carry a VOM or DMM with me.

I don't even have a DMM, i got a VOM, wasn't my choice.
post #2 of 11
How to Build the CMoy Pocket Headphone Amplifier
post #3 of 11
Thread Starter 
Quote:
Originally Posted by tomb View Post
Yeah i think i need to take a deeper look at that.
Cmoy looks so simple, IMO its not, cause i don't know anything...
post #4 of 11
You just pretty much double everything in the amplifier section in the schematics, except for the opamp of course

You have to make similar connections for both channels. You'll just have two input and output connections to the opamp. That's it.
post #5 of 11
Quote:
Originally Posted by diff_lock2 View Post

Also i was looking for a "understanding" of the cmoy, other than the headwize one.
Like why there are caps in series with the signal.
And why there are resistors on the way to ground...
The CMOY consists of 4 basic building blocks.

Power Supply
Volume Control
High Pass Filter
Non Inverting Op Amp


Start here
http://en.wikipedia.org/wiki/Operati...lifier_circuit

The high pass filter as used in the CMOY is discussed here:

http://en.wikipedia.org/wiki/High-pass_filter


The two classic books to get are The IC Op Amp Cookbook by Walter Jung and the Active Filter Cookbook by Don Lancaster. Amazon carries both of them. There's a good chance you can get one from you local library or find them used somewhere.
post #6 of 11
Quote:
Originally Posted by diff_lock2 View Post
I can't seem to find a schematic anywhere for a dual opamp based cmoy.
Could it be that opamps are so different from each other?
Double the schematics except the opamp. Look at your opamp's datasheet to look out for pin order.


Quote:
Originally Posted by diff_lock2 View Post
Is there any way to run a mono pot... cause i can't find stereo versions (dual signal)...
Dude, where are you looking for pots. Every damn shop has 'em, even my crappy home town's electronic shop has them stocked. And if you are from Finland, look at this FAQ. They have every local webshop listed, and every of them definately carry stereo pots.


Quote:
Originally Posted by diff_lock2 View Post
Oh and i was thinking of putting like trimer pots on some resistors just to see what it changes, that might help me understand somthing... and tune the cmoy?!!?! but then there are 2 channels and i would have to match the resistance for each channel, and i dont carry a VOM or DMM with me.
I dont see why the resistors should be "tuned", unless you want to play with the gain. I would rather socket pins and swap regular metal films when it is needed. You can get these sockets easily by breaking IC sockets for example.

You dont need a DMM for a cmoy, but they help alot during debugging. My first cmoy worked well without debugging tho. Cmoy is quite simple and you can solve most of the problems just by tracing the schematics in your build.

Most importantly, read Tangent's tutorial. It is quite self-explanatory and should answer all your Qs.
post #7 of 11
Thread Starter 
@yen
Yeah i think socket pins would be a much better choice.

I use Triopak. Took me a while to find my around that FAQ site, since i can barely read fin.

But i think i saw some other store around turku too (on that site), ill check if i can find it too.

I'm checking out Tangent's tutorial... but haven't got very far atm.

And about the pots, i asked for a stereo pot with a switch too... i think they have norm stereo pots, but i wanted a switch, so the cmoy would look better...(tomorrow) im going to see if i can get a opamp, dono which one yet though, something cheap. i dono if they have them all so i have to get a list a see what they have.


EDIT: why is there a high pass filter? Is it just to omit useless freq? Better for the opamp?
post #8 of 11
Quote:
Originally Posted by diff_lock2 View Post


EDIT: why is there a high pass filter? Is it just to omit useless freq? Better for the opamp?
Sorta. The real reason is you don't want to pass amplified DC through to your headphones. Its bad for them. The filter blocks DC. If you have room, a 1µF cap might be better.
post #9 of 11
Thread Starter 
well now that part makes sense...kind of...

so you mean a 1µF as part of the high-pass would be better than just the resistors? if so, then i might as well stock up on a couple of 1µF caps...

Well at least this is going somewhere...
post #10 of 11
Quote:
Originally Posted by diff_lock2 View Post
well now that part makes sense...kind of...

so you mean a 1µF as part of the high-pass would be better than just the resistors? if so, then i might as well stock up on a couple of 1µF caps...

Well at least this is going somewhere...

The high pass filter is C2 and R2 in Tangent's schematic.

http://tangentsoft.net/audio/cmoy-tu...angent-sch.pdf

His values are .1µF and 100K. That will work fine. If you have room, you could substitute a 1µF capacitor for C2.
post #11 of 11
If you cant read and understand a schematic as simple as the CMoy's is, than build the CMoy excatly as is specified on Tangents site. Parts arent too expensive. THAN if you get it working correctly (read through the 2 ongong threads of 2 people that cant get their CMOy working), build a second one with single channel opamps. Relise however you will not gain anything in sound quality. There are only a couple of high end opamps like the OPA627/637 than are not available in dual channel and it would be a lot easier to use a browndog adapter to mount 2 single channel opamps to a dual channel adpater. Remember dual and 4 channel opamps are made to be perfectly matched. If you want something with single channel opamps in the design build a different amp! The PPA and M³ are both single channel opamp based amps.

Bottomline: Modifiying the CMoy design to accomadate 2 single channel opamps is not for someone new to electronics.
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