[specto]

So I made a cmoy desktop amp, very simple, sold to me by Zigis, But of course I am having problems..... I don't know why because I can't seem to find anything wrong with my connections except for my not so good soldering skills, but it seems like everything should be ok. There is a constant buzzing sound. When I touch the volume, the buzzing goes away, but with a source plugged in I still hear buzzing plus there is a distinct clicking like noise. I feel stupid, because this is a super simple build, but who knows what I did.

 

[Aynjell]

Quote:

Originally Posted by specto /img/forum/go_quote.gif So I made a cmoy desktop amp, very simple, sold to me by Zigis, But of course I am having problems..... I don't know why because I can't seem to find anything wrong with my connections except for my not so good soldering skills, but it seems like everything should be ok. There is a constant buzzing sound. When I touch the volume, the buzzing goes away, but with a source plugged in I still hear buzzing plus there is a distinct clicking like noise. I feel stupid, because this is a super simple build, but who knows what I did.

Check all your grounds. 1 ground from each jack, and either 2 or 1 ground from the volume pot (My pot, all the prongs were in a straight line, grounds were next to each other so I just bend them together, added some solder and ran 1 ground wire). I got the click sound when my grounds broke away from the board. What I ended up doing was running a wire away from the virtual ground and having everything meet in the middle in one big glorious ball of solder. Not the best way but it works.

You definitely have a grounding issue though (I had the same experience with bad grounds on my setup, afterall I had to fix it with my hodgepodge ground). Check all your grounds, if need be, de-solder them and re-solder them. You should fix the issue. Is this a protoboard or a pcb?

 

[linuxworks]

clear photos of what you have (at various angles) might help.

 

[specto]

Quote:

Is this a protoboard or a pcb?

This is a pcb

Quote:

clear photos of what you have (at various angles) might help.

Unfortunately, I don't have a camera.

That' the board. Am I supposed to add another ground or something... it seems like it is supposed to ground around the outside of the casing

 

[Zigis]

Check all soldering points one more time, maybe somewhere is cold soldering.
Measure voltage between ground and chip power legs or on el caps. Both voltages need to be equal, then measur DC offset in both channels. Do you ground pot's shaft?

Maybe something with your source/cables, maybe PS ?

Amp have to work absolutely silent, without any hum or buzz, I build several without any problem.

Zigis.

 

[specto]

I'll try all of that tonight, I checked the soldering yesterday, but I may have missed something. I did ground it using a resistor leg attached to the potentiometer like you said and tested that to make sure it was grounded. I thought it might be my power supply, but that wouldn't effect ground right? I tested the cables as well, and I think they're fine, they're mogamis so they should be shielded correctly etc, but I'll try some other cables if I can find some.

Any idea what the clicking was though? That's what really bugged me

Zigis, could you post a hi-res picture of both the top and bottom of the board soldered, in different angles if possible ? I would really really appreciate it, I know it's asking a lot.

 

[Aynjell]

Quote:

Originally Posted by specto /img/forum/go_quote.gif I'll try all of that tonight, I checked the soldering yesterday, but I may have missed something. I did ground it using a resistor leg attached to the potentiometer like you said and tested that to make sure it was grounded. I thought it might be my power supply, but that wouldn't effect ground right? I tested the cables as well, and I think they're fine, they're mogamis so they should be shielded correctly etc, but I'll try some other cables if I can find some. Any idea what the clicking was though? That's what really bugged me Zigis, could you post a hi-res picture of both the top and bottom of the board soldered, in different angles if possible ? I would really really appreciate it, I know it's asking a lot.

If it's a really steady and fast popping the clicking happened when I lost all my grounds, I am not sure if it's evident of one specific ground not being attached, but for me it was something I ran into with all my grounds disconnected. I'd simply make sure all your grounds are in order.

 

[Zigis]

Tray to remelt/resolder all connections, especially connections to ground - both el caps, railsplitter, R2, R3, pot, there is cold solder somewhere.

Check voltages and especially DC offset, before connect phones. Safe is less than 40 mV, however with OPA2134 DC is usually between 0.3 - 7 mV

I haven't at home any ready amp, maybe I try to solder one yesterday.
Zigis

 

[specto]

Quote:

Originally Posted by Zigis /img/forum/go_quote.gif Try to remelt/resolder all of the connections, especially the connections to ground - both el caps, railsplitter, R2, R3, pot. Most likely there is cold solder somewhere. Check voltages and especially DC offset, before you connect your phones. Safe is less than 40 mV, however with the OPA2134, DC is usually between 0.3 - 7 mV I don't have an amp ready right now, but maybe I will solder one tomorrow. Zigis

Thanks, I will re-solder I suppose, time to find a solder pump.

 

[Aynjell]

Quote:

Originally Posted by specto /img/forum/go_quote.gif Thanks, I will re-solder I suppose, time to find a solder pump.

Just heat each contact up and make sure it's all sealed correctly, no need for a solder pump at this time except for extremely difficult (read: flat with no texture or anything to grab onto) solder points... I'd do those last. Do all the easy ones on the under side of the board, if that doesn't fix the issue move on to the harder ones. Star by re-soldering the grounds though, that might save time.

 

[specto]

Thanks for the input guys, I resoldered everything, and tried it again, same issues. So I was like, next step is to test different cables, considering I had never used them before, so I found a pair of some cheap old rca ic and lo and behold it works beautifully. So I may want to get a different opamp, but that's a different story. Time to talk to the guy who made my interconnect....

 

[diditmyself]

What opamp do you use? Resistor values for feedback and input? Could it be the opamp oscillating?

Can you show us a picture of the bottomside of the board so we can see that the pot correctly grounded.

I guess there's a TLE2426 used as virtual ground. Are the electrolytic caps rail-to-rail or rails to ground? I've had issues with TLE2426 with too large rails-to-ground caps. What's the cap size?

 

[Zigis]

Nice to hear you finally got amp working. Maybe it was cables from the beginning ?
You can use almost any dual audio opamp, or two single opamps on addapter.
You can read large tread about opamps here:
http://www.head-fi.org/forums/f6/opamp-thread-432749/

diditmyself,
This amp is with OPA2134, gain 6 (feedback 4.7k, 1K), 100k input to ground before pot, no input caps, 2 x 470uf Panasonic FM powercaps.
What kind of issues you had with too large power caps? Newer heard about this before.