Schem. vs. My Veroboard, Simple Headphone amp.

[WhenBoredomPeaks]

Hi guys:

This is the CMoy headphone amplifier:

Power section:



Amp section:



My layout:



(the in-out stuff means you can connect the wires to any holes under the words, also i left out the led and changed the 1k resistor to 2k for lower gain and swapped the capacitors to higher valued ones, these things are common practice with this amp as i saw from it's site.)

The reason i posted this here: This is the only forum i know where are guys familiar with turning schematics into vero/perf/other boards. Also it is on the other side of guitar playing/music making: the listening side.

I came up with a veroboard layout for this, with big spaces between parts to avoid confusion, soldering errors and stuff.
Actually it was a nice project for me because i had to venture into the world of expensive hi-fi opamps and capacitors.

But i made a mistake somewhere along the way. After a few hours of debugging i gave up.

Here's a pinout for my opamp: http://focus.ti.com/lit/ds/symlink/opa2132.pdf It's the second picture.

I swapped the opamp with a TL072, checked all the copper rows for wrong connections, tried different input voltages from 9v-24v, and the problem were the same.
Only the left side of the earphone worked and it did it with distortion.

So could someone compare my layout with the schem, please?


I can post close up pictures from both sides of the veroboard if someone need it.

Here's the site i used for the build: http://tangentsoft.net/audio/cmoy-tutorial/ It is a brilliant site for the absolute noobs.

(FunFact: the 1uF input caps were so big, they couldn't fit into a Hammond 1590B, as you can see C1 and C2 (both 0,22uF) are still huge.)

[petemoore]

  I would take voltage measurements and look for bias.
  Inline opamp ?, I'm not familiar with the pinout..look for about 1/2v's on the inputs and output.
  Make sure the grounds, 9+ and 9- are where they should be.

[WhenBoredomPeaks]

  I would take voltage measurements and look for bias.
  Inline opamp ?, I'm not familiar with the pinout..look for about 1/2v's on the inputs and output.
  Make sure the grounds, 9+ and 9- are where they should be.

http://focus.ti.com/lit/ds/symlink/opa2132.pdf

The second pic on the first page is the pinout of this opamp.

Using a 12V power source:

There is +12V between the "positive IN" and "negative IN"
-6V between "negative IN" and ground.
+6v between "positive IN" and ground.

+6v between opamps V+ and ground.
-6,2 between opamps V- and ground.

I guess i should look after AC on the inputs and outputs right?
The sad thing is that my multimeter can measure only DC volts and ampers in this small range. It have two settings for AC volts: 200 and 500, i guess both is too high.

I did connectivity tests: the output and input jack's grounds are connected, the input cables jack is connected with the circuits connecting points.

[Electric Warrior]

I came up with a veroboard layout for this, with big spaces between parts to avoid confusion, soldering errors and stuff.

wow, it's huge. but that makes it easier to mess up. so easy to lose count of the holes. and you still can get solder bridges between traces.

[WhenBoredomPeaks]

I came up with a veroboard layout for this, with big spaces between parts to avoid confusion, soldering errors and stuff.

wow, it's huge. but that makes it easier to mess up. so easy to lose count of the holes. and you still can get solder bridges between traces.

I checked this 5 times already and tested all the trace lines for bad conncetions.

Im so devastated that i will actually going to trace out the schematics from this finished non-working amp and will compare it with the original schem.

[WhenBoredomPeaks]

Ok, it looks like it's time to kill myself:

After i desoldered the parts which were important or i only had one of each (caps, jacks and stuff) i breadboarded the caps and tested them with guitar signal. They were fine.

Then i tested my in/out jacks with a cable plugged in and did connectivity tests. They all were fine.

The accidentally i touched the right output point of the jack cable while testing the ground connection and the multimeter did a horrible beep.

I was like: 

It turned out that my input jack was faulty and it connected the right input to the ground somewhere deep inside.

[WhenBoredomPeaks]

I finished this stuff (and used way bigger caps, 1uF WIMA-s, their size is 13x5 holes on the perfboard and about 3cm tall )

This is the new layout:


(that wire under the opamp is a ground connection for the in-out jacks.)

It looks a bit different in real life, for example i bent the leads of the electrolytes to a 90degree corner-like shape.

It sounds great altough it has a higher background noise than my soundcard but maybe it will disappear if i will put it into a metal enclosure. The noise remains unnoticeable during music so it is not a big problem.

I think the folks with the better (and harder to drive) headphones should definitely try it. For example my ipod absolutely fails at driving it. And this is not a loudness problem but more like a soundquality problem.

Here's the original site: http://tangentsoft.net/audio/cmoy-tutorial/

[ringworm]

Is there an equivalent for the OPA2132 that can be used, notes on the original project page suggest that a TL072 will give noise as you point out in your results.
Any ideas for another option, not sure i can find the OPA2132 in UK, I'd like to build this.

[WhenBoredomPeaks]

Wow, that's embarrassing to see, how bad my first layout was.

Anyways, here's a list of a lot of low-noise, quality opamps: http://tangentsoft.net/audio/opamps.html

I have built the circuit and it sounds awesome with my Sennheiser HD555. There is a slight background noise but it comes from the computer imo.

[Quackzed]

that layout is....
awesome!!!
you should stick some of those gooley eyes on the electrolytic caps!
for added mantis mojo!