Need help wit CMOY
Dec 29, 2007 at 9:49 PM Thread Starter Post #1 of 14
HPIMTRACER

HPIMTRACER

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i just made one of the cmoy amps and i get music with fuzzy noise when the head phones are plugged. in sounds as if there being amplified to much.. Can this happen? i didn't install a pot because i didn't see any in any near by stores. Can the pot be the reason the headphones sound like they have to much power.. I was using apple ear buds when testing to let you know. Last question is what stores sell the pot needed for this amp, the Alps RK27 or something similar
thanks
 
Dec 29, 2007 at 11:04 PM Post #2 of 14
Fuzzy noise may come from the source. Connect the amp with the other source and see if the noise goes away. I would set the gain of the amp less than 3 when there is no pot installed. Default gain of 11 i think is too much even with the pot. You may want to lower the gain of your amp. How to? Read original cmoy article at headwize.com. tangent has some alps pot.
 
Dec 30, 2007 at 12:34 AM Post #3 of 14
I was reading the basic trouble shooting and it says i need 18 volts to pass a signal when using a certain amp.. do i used the dual op amp from radio shack that was on the parts list..the TL082/TL082CP Wide Dual JFET Input Op Amp (8-Pin DIP) ..does this one require 18 volts
 
Dec 30, 2007 at 12:45 AM Post #4 of 14
The TLE082 does not require 18 volts

The maximum power supply you can use with the TLE is +18/-18 (36 volts)

18 volts split into +9 volts and -9 volts (as with the cmoy you are building) should be just fine powering that chip (being half of the MAX value)
 
Dec 30, 2007 at 1:55 AM Post #6 of 14
Quote:

Originally Posted by HPIMTRACER /img/forum/go_quote.gif
okay.. i understand what you are saying but dont know if i have +9 volts and -9 volts.. i have 2 9 volts wired in series.. will that give me +9 and -9?



Yes - you're probably using a resistor divider which will split the 18v (your 2 9volts in series) into +9 and -9
(This is assuming you're building the original CMOY to spec - it should have 2 resistors of 4.7 K each splitting the battery voltage for the opamp)

Check out tangent's ground schemes - specifically 'Resistor Divider' (which is how the original CMOY was configured/designed)

Virtual Ground Circuits
 
Dec 31, 2007 at 10:36 PM Post #8 of 14
Running it without the pot would be the same as running it with the volume turned all the way up, which could easily be causing the op-amp to clip, giving you your fuzzy noise.
 
Dec 31, 2007 at 11:41 PM Post #9 of 14
Quote:

Originally Posted by BrianDonegan /img/forum/go_quote.gif
Running it without the pot would be the same as running it with the volume turned all the way up, which could easily be causing the op-amp to clip, giving you your fuzzy noise.


That would depend on whether or not the output of his source has a built-in volume control (eg. headphone out), or if he's using the more conventional line-out with a fixed output which would definitely cause this amp to clip along with destroying the headphones.
 
Jan 7, 2008 at 11:00 PM Post #12 of 14
Okay got the pot today and it has the fuzzy noise still.. it goes away when i touch the bottom of the board in a certain spot..if your looking at tangents picturesAssembling the Amplifier its the pin half way down the board in front of the black wire is where i touch and the noise goes away... i also only hear things out of the right channel i hear a little of the music out of the left but not nearly as much from the left? any suggections on what i should do?
 
Jan 7, 2008 at 11:58 PM Post #13 of 14
reflow the solder joints, and make sure there are no solder bridges. clean up the leftover flux too with rubbing alcohol.

if possible get another op-amp, yours might be funky.
 
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