Ringing in right channel with overtones

[Nignoog]

It is present with the volume all the way up. I haven’t tried with it all the way down. I will give that a shot this evening.

I have the clip leads already. I can’t find any surplus stores in Manhattan so I am turning to Amazon. I see a number of shapes and sizes. If this is adequate as far as capacitors go, I will order it and have it shipped ASAP:
https://www.amazon.com/2pcs-Nichicon-VX-Axial-Capacitors/dp/B0745JXD6W/ref=mp_s_a_1_4?ie=UTF8&qid=1537211416&sr=8-4&pi=AC_SX236_SY340_QL65&keywords=1uf+250+volt+nichicon&dpPl=1&dpID=41xILzLahZL&ref=plSrch

Once I receive the capacitor, what’s the next step? While frustrating, this type of diagnostics is exciting!

[Paul Birkeland]

This is a bit more typical and less fussy about hookup:

https://www.amazon.com/Panasonic-ECQ-E2105KF-Capacitor-Poly-250Vdc/dp/B00MEJDGM4/ref=sr_1_1?s=industrial&ie=UTF8&qid=1537227816&sr=1-1&keywords=1uf+250+film

When you have it, connect one end to terminal 3, then carefully connect the other end to A7, then power the amp up and see if the noise is still present.

[Nignoog]

To answer your previous questions, the volume pot does NOT affect the whining/ringing sound. I turned it all the way down and all the way up and it made no difference.

Thank you for your recommendation. I have placed the order and it should arrive next week. I will do as you say and post an update after. Fingers crossed...

[Nignoog]

I think we are close to marking this as solved. I got my hands on a spare 6080 tube and 12AU7 tube. I replaced the 6080 that came with my amp and lo and behold most of my issues are gone. No more ringing or whining in the right channel. It is totally silent in both channels. So for anyone else who is having a similar problem, try replacing your power tube!

Is my tube under warranty? I purchased the amp earlier this year.

The only persistent issue is the channel imbalance which I have been wrestling with for a while. I will spend some more time with the new tubes and see if they alleviate some of the imbalance. I followed the advice here: https://bottlehead.com/smf/index.php?topic=9615.msg89805#msg89805
and attached my black (negative lead) to the ground where my power cord plugs in. I used the red (positive lead) on the RCA inputs and the values were neglibly off, favoring the R channel. I did the same on the potentiometer and, again, the values were slightly off, favoring the R channel. When I got to terminal 6 and 10 the values were WAY off! Below are the values at half and full volume with a 60 hz tone.

Center Pin RCA half volume
R: .117
L: .115

Middle lug on each level of the volume pot half volume
R: .117
L: .116

Half Volume:
Terminal 6: .254
Terminal 10: .164

[Nignoog]

I am not sure if this is helpful but the two pins that connect to the LEDs buzz when I poke them with a chopstick. No matter how many times I reflow their joints or adjust their positions in the socket, I can't seem to get them to stay quite when I poke them.

Another observation that might help you help me diagnose this problem is when I turn the potentiometer all the way down and slowly turn it up the right channel rises first, which I understand is normal at very low volumes, but it seems like the differential never evens out as I continue to turn it up.

And the last observation is the right (louder) channel seems to possess a broader spectrum of sound and color. When I turn the headphones around on my head, wearing the right channel on my left ear and vice versa, it seems as though it's not just volume but sonic depth, if that makes sense, that is unbalanced beyond just amplitude.

This is, hopefully, the final frontier of crack issues I need to resolve. Looking forward to your response!

[Paul Birkeland]

Middle lug on each level of the volume pot half volume
R: .117
L: .116

With the volume pot part way up, these AC voltages should be less than what you have at the center pins.

Half Volume:
Terminal 6: .254
Terminal 10: .164

Did you try a spare 12AU7?  If your DC voltage checks pass, this is almost certainly a soldering issue somewhere in the amp.

[Nignoog]

Thanks for your prompt response. The support here is truly incredible.

I measured the AC voltages on the pins that are directly connected to the RCA connections (far left if the RCA connection is closest to you). I will remeasure the AC voltages on the top and bottom center pins and post those.

I will try another 12AU7 and see what the voltages are for Terminal 6 and 10. If they are the same or comparable, any suggestions where to start with the soldering? Which terminal is closest to the desirable number range? Is terminal 6 too high or is terminal 10 too low? Should I just follow the wires that go from the RCA and reflow everything they touch?

[Paul Birkeland]

I would honestly just reflow them all.  It also wouldn't hurt to post your DC voltages on terminals 1, 2, 4, 5, 7, and 9.

-PB