Help with OPA604AU

[moshi]

Yes.

i thought you were talking about these kind of terminal

 

[moshi]

One of these resistors has an unreliable contact. Most likely, this is the 417th

can i replace this with 10k ohm resistor?

 

[moshi]

I believe this implies the noise has to originate before the + input. As a diagnostic test, I suggest removing R409 and installing a short across from + input to ground. You won't have any audio, but there should be no erratic noise. If no noise, remove the short but leave R409 open; now you're testing R411 as the noise culprit.

VR402 200KB is my volume control, and the noise is not affected by the volume knob, i think its not coming from L1 its after the VR402, can i replace R417 with 10k resistor instead of 18k?

 

[BSST]

I would go for higher value in preference to lower. The opamp has very low bias current, plus you want to maintain high available gain to drive the feedback connected through C409.

 

[moshi]

I would go for higher value in preference to lower. The opamp has very low bias current, plus you want to maintain high available gain to drive the feedback connected through C409.

thanks

 

[moshi]

I would go for higher value in preference to lower. The opamp has very low bias current, plus you want to maintain high available gain to drive the feedback connected through C409.

Is having Op-Amp this close to a bipolar cap can cause issue?

 

[Mark Tillotson]

I doubt there's any appreciable noise on the cap its role is to short-circuit all the noise. Assuming its a decoupling cap, that is.

 

[moshi]

I doubt there's any appreciable noise on the cap its role is to short-circuit all the noise. Assuming its a decoupling cap, that is.

thanks