Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › Cmoy problem ( please help )
New Posts  All Forums:Forum Nav:

Cmoy problem ( please help )

post #1 of 8
2/6/05 at 6:52am
Thread Starter 
Help Please,
This is the second cmoy I have built, the first worked fine so I built one for a friend.
I have used the same parts apart from using an opa2227 op-amp, and I now get hiss.

The hiss is present when I don’t have anything connected to the input, if I put my interconnect in it goes away, but can hear it again when I play music. Also if I tap the input wires from the jack I can hear the tap through the headphones.
Reply
post #2 of 8
2/6/05 at 7:13am
If you're getting hiss with the source disconnected, add R5. This should clear the hiss up.

If you are also getting hiss while playing music, check your grounds for bad joints and make sure they're connected well.
Reply
post #3 of 8
2/6/05 at 7:36am
Sounds like an offset problem to me.

Yes, I'd also be checking All joins in the signal path, cos if the join is bad there, then you can get noise.

Don't add the R5 if this is a hiss reduction problem, this will just make it harder to troubleshoot.

There is definetly A problem with the amp if you get clicks when you tap it.
Reply
post #4 of 8
2/6/05 at 7:50am
Thread Starter 
Sounds like an offset problem to me.

I saw this on tangents site when trying to trouble shoot the problem myself but I'm not sure what it is?

I thought it maybe a ground issue, so i am going to remake the jacks and wiring.
Reply
post #5 of 8
2/6/05 at 7:52am
Good idea.

The quickest and easiest way to test for dc offset is the get a crap set of headphones.

And push and pull the plug into the jack with the headphones either on or near your ears.

If you hear a defening click then you know that is the symptom and main problem.
Reply
post #6 of 8
2/6/05 at 7:55am
Thread Starter 
sorry @sia@home I still dont understand what DC Offset is ?
Reply
post #7 of 8
2/6/05 at 12:51pm
Thread Starter 
I have checked voltages as per tangents guide, this is what I get
Pin 4 -V = 4.32 v
Pin 8 +V = 4.3v

but with my DMM set at 200m I get the following the DC voltage from output ground to the amp's left and right outputs are,

Left Channel 06.8
Right Channel 01.2
Reply
post #8 of 8
2/6/05 at 1:08pm
Quote:
Originally Posted by star1

The hiss is present when I don’t have anything connected to the input, if I put my interconnect in it goes away, but can hear it again when I play music.
What headphones are you using for testing. If they are low impedance you're more likely to hear hiss and that's the type of noise that R5 is meant to help.

Leave the interconnect in place, but put the player on pause. If you can still hear the hiss, add R5. If the hiss stops with the player on pause and the amp at a normal listening volume, then the source of the hiss is really the player or the recording itself.

(those numbers you posted further down the thread look normal to me.)
Reply
New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › Cmoy problem ( please help )