Cmoy pot Ω value
Aug 3, 2013 at 9:05 AM Thread Starter Post #1 of 18

logosway

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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?   
 
Aug 3, 2013 at 9:07 AM 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
 
Aug 3, 2013 at 9:27 AM 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.
 
Aug 3, 2013 at 10:56 AM Post #4 of 18
Are you certain you didn't buy a linear taper pot?
 
Aug 3, 2013 at 8:10 PM Post #8 of 18
Quote:

 
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

 
Aug 4, 2013 at 2:30 PM Post #9 of 18
Quote:
 
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?
 
Aug 4, 2013 at 8:17 PM 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.
 
Aug 5, 2013 at 6:09 AM Post #11 of 18
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.
 
Aug 6, 2013 at 4:17 AM 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.
 
Aug 6, 2013 at 5:49 AM Post #15 of 18
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::
 

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

 

 

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