Sound output problems - No stereo [solved]

[swich401]

I recently finished my mainline build but have run into a problem:

I have my headphones connected via the balanced XLR output. Output switch set to balanced and impedance switch on high. Music that should be in stereo (i.e. separate sounds should be given to the left vs right ear) is coming through in mono, and is very "closed in" (muffled?). If I switch the output to unbalanced, and plug in either through the XLR or through the TRS the sound becomes more stereo (may still be a good degree of crosstalk), but much louder in the right headphone channel than the left.

Changing RCA inputs does not fix the issue. Unplugging either the left or right RCA one at a time; sound still comes through as mono and muffled.

NOTE: All voltages and resistances check out fine as far as I can tell (I can post all of the specifics readings I'm getting with my meter if it would help). Tubes were biased according to the manual to 145V. All LEDs light up. I gave the system around 15 hours of burn-in to see if that would do anything; It did not.

[Paul Birkeland]

Can you run just the left channel to determine whether this issue happens with both the balanced and unbalanced outputs?

This is very certainly either a solder bridge between two switch pins on the balanced/unbalanced or impedance switch, or a miswire at one of those switches.

The best way to diagnose these is to very, very slowly go through each step in the manual relating to wiring the outputs, then check over your work. 

You can also post photos here of that particular area of wiring - we can compare against the manual and use your symptoms to point you in the right direction.

-PB

[swich401]

Thanks for the help Paul! Found a miss-wire on the coarse attenuator switch, fixed the problem.

This amp sounds fantastic!

[Paul Birkeland]

Ah, good catch!

[dubiousmike]

Congrats swich!  Nice job on your output cap circuit too - enjoyed your photo!