[andrep182]

Hi guys, this is my first post and I hope I can get help on my project for fun =). I built a CMOY amplifier based on the schematic below with OPA2132:
 
http://tangentsoft.net/audio/cmoy-tutorial/misc/cmoy-tangent-sch.pdf
 
I did make some tweaks such as the following:
- Better ground with TLE2426 based on http://tangentsoft.net/elec/vgrounds.html
- adding 200nF in parallel with R4 (for better bass)
- 1uF film capacitor as C2
- 470uF as C1
 
Using a 9V battery, it works like a charm. However, using a DC programmable power supply (PST-3202), I got a mix result depending on headphones:
1) Using My normal earbuds (tried 2 different ones), the sound is good
2) Using my sennheiser HD555, at lower volume I'll hear nothing but medium buzzing. As the pot is turned more and more, the sound from the MP3 player will start to play but the bass handling is really poor
 
If I do my research correctly, HD555 should have a higher impedance than earbuds. I also should mention that I use the 6.4mm to 3.5mm adapter for my HD555, which should give it even a total higher impedance:
http://www.shopzilla.com/hosa-technology-6-14-trs-to-35mm-trs/4882009437/compare?br=13831629078881409401109990099011485&fromblip=1
 
In attempt to troubleshoot, I did the following:
- added extra bypass capacitor 330uF across the 9V battery
- lower the gain from 10 to 5
 
Both attempts didn't help either and I rather confused now. I was hoping somebody can give me some advise on what else I could try. Thanks in advance!

 

[tangent]

Is your wall supply isolated? The link goes into the PIMETA v2 docs, but the same point applies to the CMoy pocket amplifier.

 

[andrep182]

  Is your wall supply isolated? The link goes into the PIMETA v2 docs, but the same point applies to the CMoy pocket amplifier.

Hey man, thanks for the suggestion. I took off the ground off the AC plug and whalaa, we're back in business =). I guess this is another reason for me to go ahead and build a boost regulator for the non-battery source