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Cmoy pot Ω value

post #1 of 18
Thread Starter 

I would like to know how is the Ω value of the POT affect the cmoy sounds. As the parts list recommends a 10kΩ pot, and I accidentally bought a wrong one which is 5kΩ. Will it fits in a cmoy running with 1 9V battery?   

post #2 of 18

If you're powering your CMOY from an a DAP through it's standard headphones port, ,it'll be fine, however if you're coming straight from a DAC it may be a bit dodgy depending on the output power of the DAC and if it has any buffering.


I doubt it'd be an issue and personally I would just try it and see

post #3 of 18

Didn't know 5ohm volume pots existed. I usually use 10 or 30ohms for small amp applications. Or just solder some resistors to a left over 50/100ohm pot to drop it down to 10ohm's if required.

post #4 of 18

Are you certain you didn't buy a linear taper pot?

post #5 of 18
Thread Starter 
Originally Posted by tangent View Post

Are you certain you didn't buy a linear taper pot?


this is what i got... Can this suit in the 1 9v battery cmoy?

post #6 of 18

That's a linear pot, you can tell by the B marking, theoretically you could use it but your volume control would not seem very natural 

post #7 of 18
Thread Starter 
post #8 of 18
post #9 of 18
Thread Starter 
Originally Posted by tangent View Post


Well, seeing as how it's the same pot as I list in my shop, I'd have to say, "Yes, it'll work". wink.gif

But I found a problem with this. I chose a Gain=3 for R3, without a POT, it sounds normal. When I put in this POT, even I turn the POT all the way up, it sounds much weaker than before. Is it normal due to the Ω value?

post #10 of 18

The total resistance of the pot doesn't affect the overall volume if you build the amp as designed.


If you use too small a value for R2, or you hook things up wrong, you can get effects like this.


If you measure resistance across the input jacks you should get 10 kΩ, regardless of volume setting. The value should also be nearly the same between the left input and ground vs between the right input and ground.


Another way this could happen is if you used Chu Moy's schematics instead of mine, and implemented his original switched 2-level volume scheme.  You need to take the switch and those extra resistors out when you put the pot in.

Edited by tangent - 8/4/13 at 5:19pm
post #11 of 18
Thread Starter 

speaking about hook things up wrong, I got some noise out and the human voice stay way behind than normal. But when I touch some solder parts, it disappears and come back again when i remove my finger. Is it related to grounding problem? 

especially when i'm touching pin 5&6. and at the right side, there is NO human voice.

Edited by logosway - 8/5/13 at 3:44am
post #12 of 18

Yes, you've done the grounding wrong. Have you read my panel components hookup article?

post #13 of 18
Thread Starter 

Yes. The case is, I am not using a metal enclosure but a PP one.

post #14 of 18

Metal cases aren't the only way to screw up grounding. Leaving a ground connection off a connector is another way, for example.


Please post high-res pics of both sides of your board, and the panel connections.

post #15 of 18
Thread Starter 

understand. As I have successfully built a couple cmoy with your layout, I am trying to scale down the layer into a really tight one, just for fun :P

Here is what I got and where the problems come::


he greens are the groundings, will connected to each other by wires.



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