[onvn]

Okay, I have finally successfully built myself a cmoy based on tangent's schematics and etched my own board. For now, just to test the circuit, I used a cheap, generic op-amp (LM833 by National, I think) from Dick Smith's (much like Radio Shack in the US) but I cant even listen my headphones on it due to crackling and heavy distortion and literally, I can only hear 2% of playing music thru headphones

. But then I plugged my computer speakers into it, with the other end to the computer and played some Stacey Kent and yes, the amp seem to do its job very well in this case, only with very little distortion.

But why is it that crackling and popping is only heard when I plug headphones into it and not on speakers? I think it is due to the op-amp but I'm curious if anybody has any other explanation.. BTW, I ordered the OPA2132 already and see if these clear things up..

 

[Seaside]

what headphones you use?
What is the gain of your Cmoy?
Is there any DC at output?
Any pic of your Cmoy both top and bottom?

 

[Joshatdot]

did you test your virtual ground when that was built? are you getting equal +/- volts on the power supply?

 

[achina]

LM833 has bipolar inputs. It will not be stable in a Cmoy circuit without modification. Tangent has an explanation on this: http://www.tangentsoft.net/audio/hs-opamp.html

Better to start with something like the recommended OPA2132 which has FET inputs.

 

[onvn]

Quote:

Originally Posted by Seaside /img/forum/go_quote.gif what headphones you use? What is the gain of your Cmoy? Is there any DC at output? Any pic of your Cmoy both top and bottom?

Seaside, I tried using both my K701 and ER6i.. The gain is 11 dB.. no DC and no camera, sorry

Quote:

Originally Posted by Joshatdot /img/forum/go_quote.gif did you test your virtual ground when that was built? are you getting equal +/- volts on the power supply?

Yes, I did. Nothing wrong with the power supply.

Quote:

Originally Posted by achina /img/forum/go_quote.gif LM833 has bipolar inputs. It will not be stable in a Cmoy circuit without modification. Tangent has an explanation on this: http://www.tangentsoft.net/audio/hs-opamp.html Better to start with something like the recommended OPA2132 which has FET inputs.

Thanks for that link.. The circuit I built is the default of Tangent's instructions and I will use it with OPA2132, it's on the way!!

 

[onvn]

Okay, I received my OPA2132 this morning (Australia) and though it significantly reduced the noises and I actually can listen to some music, it is still not possible to use this cmoy.. I checked all the circuit connections and am getting equal voltage +/- and very little to no DC in the output and now, I have hit a brick wall..

Another thing I found out is that it does crackle and pop when I turn the volume on my computer speaker down to a minimum and boost the volume with the cmoy.. So i guess this has something to do with power? because when the power of the speakers are lowered and increased the power of the cmoy, it does that.. (?)

Just so you know, this is my first project and if this is what DIY audio is like, I quit!!

..or wait till grandpa comes over and teaches me.. (grandpapa is a prolific amateur radio fanatic back in his days..)

 

[achina]

Are you plugging the Cmoy into the amplified output of some pc speakers? Try plugging it directly into your computer's line out. Or better yet a portable CD/mp3 player.

 

[onvn]

Quote:

Originally Posted by achina /img/forum/go_quote.gif Are you plugging the Cmoy into the amplified output of some pc speakers? Try plugging it directly into your computer's line out. Or better yet a portable CD/mp3 player.

Nop, I plug it into the lineout of pc, then plug speakers/headphones into the output of the cmoy. I also tried with my ipod but it still doesnt work this way.

I tried plugging K701, ER6i and a passive small plug-in speaker (cheap ones you can get for ipods) with laptop and ipod as source - the result is a heap of noise but when I plug in an active computer speaker (bose companion) it works fine, unless I turn the volume down low and boost volume with cmoy (as i mentioned abive)

 

[fortney]

verify that you have no solder bridges using magnification and the continuity checker of your VOM or DMM, be sure the jacks are properly connected to the circuit and grounded, check for sub par soldered joints and heat them up to remelt the solder...most of my failures have been obvious once I discover them and not obscure electronic phenomenon.

Have the schematic in front of you as you work.

Also take a break as needed and go back to it later.

F