Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: Nignoog on September 11, 2018, 03:18:48 AM
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When i turn my crack + speedball on a faint but constant ringing occurs in the right channel. It is unaffected by volume. Sometimes it cycles up through an overtone series. It might be psychosomatic, but it feels like it creates pressure in my right ear. With music on it’s not so bad, but when things are silent, it’s very obnoxious. Wondering how best to troubleshoot it.
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Frequently an issue like this can be caused by pollution from nearby electronic devices, especially those with wireless capabilities.
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Thanks for your prompt response Paul. I live in an apartment in Manhattan so there are A LOT of wireless devices around. Two follow up questions:
1. I feel like I did not have this problem until recently. Are there any other causes I could try to rule out besides wireless frequency interference? I will try plugging it in at different outlets and see if that ameliorates the problem.
2. Why would it only affect one channel and not both?
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Try cleaning the tube pins. Dirty pins can make tubes oscillate sometimes.
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I will give that a shot. Will Hosa Deoxit contact spray do the trick?
What causes the oxidation? I live in NYC so it’s been very humid. Anything I can do to prevent this in the future?
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I plugged the amp into my an outlet in my bedroom and bathroom but the ringing continued in different spaces. And I cleaned the pins on both tubes but there is still a persistent ringing in the right channel. Any other ideas?
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Have you tried turning off your phone?
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Yes. I am almost positive it is not the phone. I experimented with moving my phone and wireless mouse closer to the amp. The interference they cause is a rhytmic buzzing or clicking sound. Moving closer or further from the wifi router also didn’t yield any change in the sound.
Here are some other observations I have made in trying to troubleshoot it:
1. Switching L and R channel chord on my HD650s. As expected, ringing continued in L channel instead of the R.
2. I plugged my HD598 into the amp and cannot seem to hear ringing, but when I plug the HD650s into another amp there is no ringing in the 650s. Could impedence exacerbate the problem?
3. When I was cleaning the 6080 tube, I could hear something clinking inside the tube. I could not see what was loose but something was moving in there.
4. This could be psychosomatic, but when I turn the amp off for second and then switch it back on, the ringing disappears and then slowly reemerges.
5. I tried yelling at the amp and scolding it, but that had no effect either.
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There could also be something riding on the AC lines in your wall that's coming through the amp. For the sake of eliminating that possibility, it's always nice to try the amp at a friend's house or your place of employment.
I've also tried yelling at my projects when they aren't working, but I haven't figured out anything effective yet.
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EUREKA! I have discovered the culprit. Before I moved the amp to another location I decided to check the power cord. I gave it a jiggle where it connects to the amp because it never seems to sit flush and the ringing stopped! Based on it's alignment, weird sounds are produced from ringing to a breathy popping sound. Now the question is, is the issue with the cord itself or with soldered parts beneath it?
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You could always try a different cord.
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I tried a different power cord and it made no difference. I tried plugging it in on another socket outside of my apartment which also made no difference. I reflowed the solder joints around where the power cable is plugged in. This made a huge difference, but there is still a humming/ringing sound that fades in and out. It is much fainter now. Could a bad solder joint be the cause? Is there any area I should focus on or should I consider doing some more reflowing around the power unit?
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You could post some build photos, maybe we can see something that could be the cause.
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I uploaded a few pictures per your request:
https://imgur.com/a/yJO2elo
In the meantime here is what I have done:
1. Reflowed almost every joint around the power supply and power tube.
2. Removed and filed the pins on both tubes in case there was any oxidation.
3. Tapped everything with a chopstick.
It seems like there is nothing I can do to stop, initiate or change the ringing/hum/whine that occurs in the right channel. It is still very soft but it's irritating and over extended periods can be a little painful.
I also changed my search query in the forum from "crack ringing" to "crack whine" and found a lot of people with similar complaints who solved their issue by cleaning their pins or getting new tubes. Based on my observations about there being something rattling in my power tube, a whine in the right channel and a slight channel imbalance in the right channel, I am beginning to suspect one or both tubes may not be functioning properly. Additionally the overtone series starts as the tubes are warming up. It reaches a constant pitch once fully heated which further leads me to believe it is tube related.
NB When I lean in very close and put my ear next to the power tube I can hear a ringing/whine.
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Is this noise present with the volume pot turned all the way down?
If you can snag a 1uf/250+V capacitor from your local electronics surplus shop and a pair of clip leads, we can isolate where the noise is entering.
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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!
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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 (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.
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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...
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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
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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!
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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.
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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?
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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