[lehtinel]

Yup, especially for a first-timer it's confusing with this type of a problem. Switched R3 for 4.7kOhm, problem persist, changer the OPAMP, problem persist. Do you thing my ground is weak? 

 

[Avro_Arrow]

Here is a schematic that shows all the parts you might
find on a CMoy. People rarely build one with all of the
possible parts. Maybe this will help, maybe not.
Also, the output resistor, if used, may be either inside
or outside the feedback loop, whichever sounds better.
 

 
Edit: Forgot power LED...duh...

 

[lehtinel]

Thanks for that! Ill see if Il'll build up another one (orderer parts for two) but would like to wait with that one and design a good wooden case for it. In the meainwhile, of course, I'd like to boost my 'DIY confidense' by making this one worlk. After the R3 change the amp starts to break up later on than before so it could have an inpact. Maybe I'll swich R4 into a 4.7komh resistor and the C2 caps to these 470nK ones I have. I have no pot in my amp currently cause I ordered a mono one by mistake.

 

[Avro_Arrow]

If you want to pick the values for your next one, using the names
from my schematic above, the parallel combination of Rgain and
Rfeedback should be in the range of 300 to 500. This is also
the value for Rsource. Rinput is 10 times the value of the volume
pot and forms a high pass filter with the DC blocking cap.
You want to tune this filter for between 1 and 5 Hertz.

 

[lehtinel]

Allright, I gave in and user new parts for a new design. used the complete width of the protoboard, ie. 19 rows. Measured resistor values, made the gain for 3 and soldered the IC right in as it had to go vore three rows of the ground row.
 
It works!
 

 

 

[Avro_Arrow]

Good job!
 
Congratulations!

 

[Avro_Arrow]

Did you ever figure out why the first one didn't work?

 

[tabacaru]

Hey,
 
New here - haven't done much DIY audio, but as a grad student in engineering I have access to some tools and it's always been something I wanted to get into. I've ordered a pair of HD650's and an Audiotrak prodigy hd2 so I'm pretty excited to get working on some things.
 
Anyway, I also started with the cmoy, and built one a couple of days ago. The sound, however, was also kind of muffled and since I could not find any mistake, I decided to simply make another one alongside. The newer one I made sounds beautiful.
 
What's strange is that if I put in an older version of the OPA2132PA (I had one lying around) even the 'muffled' amp sounds good - albeit with a lot of hiss in the background. Since it seems that I'm not the only one with this problem, I will test a few things with my oscilloscope and wave generator this week and let you know what I find the problem to be.

 

[Avro_Arrow]

First off...welcome to Head-Fi and sorry about your wallet...
 
It would be great if you could discover the problem.
Congratulations on your successful build!
 
Quote:

Hey,
 
New here - haven't done much DIY audio, but as a grad student in engineering I have access to some tools and it's always been something I wanted to get into. I've ordered a pair of HD650's and an Audiotrak prodigy hd2 so I'm pretty excited to get working on some things.
 
Anyway, I also started with the cmoy, and built one a couple of days ago. The sound, however, was also kind of muffled and since I could not find any mistake, I decided to simply make another one alongside. The newer one I made sounds beautiful.
 
What's strange is that if I put in an older version of the OPA2132PA (I had one lying around) even the 'muffled' amp sounds good - albeit with a lot of hiss in the background. Since it seems that I'm not the only one with this problem, I will test a few things with my oscilloscope and wave generator this week and let you know what I find the problem to be.

 

[tabacaru]

I doubt my wallet will ever forgive me... by the way, I'm in Toronto as well.

 

[lehtinel]

Quote:

Did you ever figure out why the first one didn't work?

No, I'll still have to work on that, but my guess would be that it has something to do with the grounding, as in the first try I kut a tree row connected path so I could follow the Tangentsoft instruction completely. 
 

 

[tabacaru]

So I did just a basic test between the two, and I came across something I can't understand.
 
(Using an oscilloscope) Both the amps output nice signals at various frequencies for both sine and square waves but the 'bad' amp doesn't output a nice sound at all. I am also starting to think this is a grounding problem due to the fact that the oscilloscope has it's own ground which is probably why it's showing a nice signal. Does anyone have any experience with a problem like this?
 
On another note, I am considering changing my 110nf input caps to a higher value ones. I didn't think it'd make that big of a difference, but actually there's quite a large phase shift at low frequencies (~20Hz). Does anyone know the highest value capacitor that would still fit in an Altoids case? I'm using Panasonic polypropylene film caps and they're quite bulky even at 110nf.
 
Thanks for any replies!

 

[tabacaru]

Annddd....... the problem magically fixed itself!
 
Edit: I lied, I was using the 'good' amp. The problem remains.
 
Edit 2: I found the problem, it was the potentiometer.

 

[Soymilk]

congrats

 

[lehtinel]

Allrigh, the first Cmoy is still working correctly, now neatly in it's case. As I had parts, and a tin-can for another one, I started a new learning process by building it with the TLE2426 rail splitter. I got even voltages across the power supply, and they are even if no headphones are plugged in. But, as I plug in phones they become uneven (+1.8v / - 5.2v) and my right channel is quieter and more easily distorted. The left channel has a good, normal sound. The soldering is far from top notch, especcially as I had the IC chip wrongly placed at first and as I swapped out the R5 position for resistors of 10kOhm and 100kOhm without much difference in sound.
 
Any help is appreciated.