[einolu]

Just finished first CMoy following tangents design. There are 2 main problems, the volume control seems to only affect one channel, so that when the volume control is at maximum, both channels are playing equally. When turned to minimum the right channel is still playing at the same volume while the left is off. It actually seems to work as a volume control on the left channel, just not the right. Im using a panasonic pot and its wired like this:

[top]
[L-out][G][G][R-out][R-in][L-in]

That seems to be right?

Also, the amp doesnt seem to be amplifying the sound very much, is this because I used a R3 resistor of 4.7K ohm or is something wrong? I thought these things were supposed to be loud...

Nothing is getting hot and there is some hiss and interference when the volume is set to max, as soon as you turn it down just a little, there is no hiss or interference.
Help!!!

 

[Madcat05]

your getting a low volume because your pot is wired wrong.

run a search as I recall someone else had this problem.

 

[Sal]

The pinout on the pot looks correct, but I would look closely at the two adjacent pins, R-out and R-in to make sure they're not bridged. Use a multimeter to make sure. That would surely result in the symptoms you describe.

It certainly should be loud, so chances are you may have some other connections bridged where they shouldn't be. Clean the solder flux off with alcohol and inspect each solder joint very carefully and check that no leads are touching each other. I would even go back to the schematic/layout and verify each and every connection to make sure they go where they're supposed to go.

A little hiss at max volume is probably normal. It can becoming from your source and it is also possible that it is coming from the amp, but with music playing, it should have a negligible effect.

 

[einolu]

well its not the pot, because when I took it out of the circuit and just had a dircet line in, I was only getting sound out of the left channel. Seems to be the circuit, and its still only a little bit louder than the original signal. Probably the soldering, but this is my second shot at making the cmoy (the first didnt work at all) and the soldering was much cleaner and there are no visible bridges, must have done something wrong somewhere along the way. Anybody have this problem before...

~EO

 

[Madcat05]

take a look at this Basic Troubleshooting for Headphone Amplifiers

 

[einolu]

no luck, too bad.

really should have just spent the $30+ on a pre-build amp...

~EO

 

[Madcat05]

don't give up yet. wait for tangent to post.

 

[ranwill]

I agree, DON'T give up. I've built 2 amps and had trouble getting both of them to work right off the bat. It's called inexperience I think. Just step back, compare and recompare to Tangent's pics, and do a little thinking. It's worth it. The sound quality will amaze you when you finally get it going.

Randy

 

[tangent]

Quote:

really should have just spent the $30+ on a pre-build amp...

If all you wanted was an amp, yes, you should have bought it from someone else. You DIY when you want more out of it than just the finished hardware.

Quote:

don't give up yet. wait for tangent to post.

Your faith in me is flattering, but I wouldn't have said anything different than your previous post.

einolu, how about it...have you followed the troubleshooting article?

 

[einolu]

yeah, actually, the only thing that seems to be to blame is the jacks themselves because everything is litiraly perfect, iv checked about 5 times. this is also my 3rd attempt... things just seem to break in my hands, heh. i should try new jacks, but I dont feel like spending any more money, maybe ill split a cheapo interconnection I have instead of getting a new jack... grr... prefect i tell you, perfect, unless the opamp was broken from the time I got it, since it has recieved absolutley no abuse.

~EO

 

[einolu]

might as well list exactly what parts I used...

checked all the resistors before I put them in...

2 1000uf 25v panasonic caps
2 .1uf 50v caps, the little blue boxes
4.7k ohm resistors for both R2 and R3
10K ohm resistor for R4
[edit]
OPA2134PA and the socket for it
R5 just a jumper basically
2 jacks from digikey (might be to blame)
1 panaonic pot from digikey (wired correctly I see)

thats all the parts that matter I think, Ill check the wiring again tomorrow with a clear head, but its perfect from what i can see, and nothing is lose, its either the jack or the opamp... also, what would make my amp "not very loud"?

~EO

 

[Sal]

I wouldn't jump to the conclusion that the jacks are bad unless somehow one of the pins was shorted to ground. That's easily checked with an ohmmeter.

"not loud enough" can be cause by either an input shorting straight to the output, bypassing the opamp, or by a problem with the feedback loop that causes the opamp to be at unity gain or very low gain. Your parts list shows R5 as both a 100k resistor and a jumper, perhaps that's a misprint. Going by Tangen't CMOY guide, you can jumper R5 anyway to get that out of the circuit to simplfy troubleshooting.

Don't get too frustrated, even experienced amp builders miswire projects too. The fact that all the wires and leads pass so close together can cause numerous problems. Look at it with a fresh eye any perhaps you'll spot the problem.

 

[Earwax]

Quote:

Originally Posted by einolu yeah, actually, the only thing that seems to be to blame is the jacks themselves because everything is litiraly perfect, iv checked about 5 times. this is also my 3rd attempt... things just seem to break in my hands, heh. i should try new jacks, but I dont feel like spending any more money, maybe ill split a cheapo interconnection I have instead of getting a new jack... grr... prefect i tell you, perfect, unless the opamp was broken from the time I got it, since it has recieved absolutley no abuse. ~EO

Instead of replacing the jacks, how about just checking continuity through them, by connecting an IC and testing that right, left and ground have continuity and no shorts all the way through from the far end of the cable to your amp.

Oh, and I just looked at your parts list. There are two R2s in Tangents list, 4.7k for the rail splitter, but the other R2 is supposed to be 100K, as in

I suppose that could be enough of a difference to cause a problem?

 

[einolu]

I guess Ill have to replace those resistors since they might be causing the volume problem. Oh, the R5 is only a jumper, that 100k resistor thing is a typo.

besides that I magically got both channels to work after I switched interconnections, haha! Now that thats settles, Ill have to wire the pot back in, still dont really get why it was acting so strangely before.

It still only seems to boost the volume just a small amount from the original, but it is loud enough for me, since the grados are easy to drive. As for sound quality it doesnt make my grados sound any better at the moment, but that could be because its not fully funcional yet, or because the SR60s just dont need a amp...

Ill let you know when I make the changes, thanks for the help so far!

~EO

 

[einolu]

Okay, so the R2/R3 in the powersupply should be 4.7k Ohm, that seems right. but according the Chu Moy the R2 should be 100k ohm and the R3 should be 1000 ohm in the audio circuit, should I change my resistors them?

~EO