Cmoy makes sound worse
Jul 26, 2006 at 8:41 PM Thread Starter Post #1 of 27
ilikepie

ilikepie

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Today i bulit my first cmoy. It works but the sound is worse then if its plugged directly to my computer. I checked for solder bridges and im sure there arent any. Could this be becuase im using cheap headphones with low impedience? Im not gonna get "good" headphones for another month so is there anything else i can do?
 
Jul 26, 2006 at 9:26 PM Post #2 of 27
Quote:

Originally Posted by ilikepie
Today i bulit my first cmoy. It works but the sound is worse then if its plugged directly to my computer. I checked for solder bridges and im sure there arent any. Could this be becuase im using cheap headphones with low impedience? Im not gonna get "good" headphones for another month so is there anything else i can do?


What do you mean when you say "the sound is worse." Some details on what your actually hearing in comparison to what you normally hear will help others troubleshoot what your problem maybe, e.g., clicking sounds, noise, etc.
 
Jul 26, 2006 at 9:48 PM Post #3 of 27
Im not really sure how to describe it but most noticable thing is that the bass is almost non existant. Everything just sounds worse. Theres no clicking or static or anything.
 
Jul 26, 2006 at 10:33 PM Post #7 of 27
Quote:

Originally Posted by ilikepie
Im using an opa2227 but i also tried a opa 2132pa. Its wired with copper ethernet cable. Im using this interconnect http://www.cui.com/pdffiles/SJ-43502PM.pdf
and this pot http://www.panasonic.com/industrial/...aok0000ce9.pdf
And yes i did change c1 to a 470 uf cap


I think the choice of C1 maybe what's doing it. I'm presuming your using an electrolytic cap right? Electrolytic caps (especially at that value) tend to be very harsh.

Try switching it with sometime like, polypropylene, polyester cap, or maybe even metal film type. You may get better results. I hope this helps.
 
Jul 26, 2006 at 10:37 PM Post #8 of 27
Wow wow wow! No electrolypic caps as input caps, that's just wrong. If you don't have a high DC offset, change the input cap to a 0.1uF polypropylene or polyester. Maybe even consider 0.47uF caps if your offset is really bad, but definitly use polypropylene or polyester and not electrolytic, they're just not meant for that.

And by the interconnect I meant what cable connects your computer to your amp.

If you're using ethernet cable as internal wiring, make sure it's CAT5 at least. I haven't heard people using this as internal wiring, but it should work since it's used in speaker cables.
 
Jul 26, 2006 at 10:39 PM Post #9 of 27
Follow Grasshpr's advice, and choose something in the ballpark of 0.1 to 1uF. Just to make sure, you are sure you didn't change R2 to another value either?
biggrin.gif
 
Jul 26, 2006 at 10:49 PM Post #11 of 27
hm.. seesm like there are actually two C1's, looking at the PSU section now... 0.47uF is fine, so it's not a trouble hi-pass filter, if R2 is still 100k. So that was not the problem. The corner freq. would be at ~3.3 Hz

EDIT: When i say R2, it's in signal path
 
Jul 26, 2006 at 11:11 PM Post #13 of 27
Last try, before i don't have anymore ideas - is the battery new / fuly re-charged? Either that or the impedance of the headphones in the bass region must be incredible high, exceeding the rail voltages...
smily_headphones1.gif
 
Jul 26, 2006 at 11:26 PM Post #15 of 27
Not really, except if it's one of those 7.2V rechargeables. You can check if it's still capable by connecting the battery with e.g. a 100 ohm resistor and measure the current flow through the resistor with a multimeter, should be ~70 mA and not drop rapidly when measuring.

But i don't think it is the problem, since a too low voltage because of current draw will make the sound distorted only
smily_headphones1.gif
 
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