Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: carlman14 on January 22, 2019, 05:45:09 AM
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Hello, I just got done building the crack (no speedball yet), and I have two separate noises that I would like opinions on.
First, there is a low hum in the left channel. It seems like it randomly gets quieter and louder, and I haven't been able to correlate it with any other part of my set-up.
Second, there is a higher pitched hum/whine/something in the right channel. This noise alternates between a couple higher frequencies. I have found that with this noise, I can tap the side of the larger tube and the noise goes away for maybe up to one second, then comes back.
Both noises stay the same volume when turning the volume knob. Both noises also seem to be more present once the tubes have warmed up a little. I have also verified that neither noise is related to upstream equipment. I can hear both even with the RCA's unplugged.
Based on what I've read in the forum, step one is to touch-up the solder on basically everything. But I was wondering with the information above, is there anywhere in the circuit in particular that I should look at?
Here are my resistances and voltages.
Power transformer secondary test (AC):
Black on 7, red on 9. Expected: 6.5, actual: 6.2
Black on 11, red on 12. Expected: 175, actual: 178.8
Resistances:
1. Expected: *, Actual: *
2. Expected: *, Actual: *
3. Expected: 0, Actual: 0
4. Expected: *, Actual: *
5. Expected: *, Actual: *
6. Expected: 0, Actual: 0
7. Expected: 2.9k, Actual: 2.99k
8. Expected: 0, Actual: 0
9. Expected: 2.9k, Actual: 2.98k
10. Expected: 0, Actual: 0
12. Expected: 0, Actual: 0
13. Expected: *, Actual: *
14. Expected: 0, Actual: 0
20. Expected: 0, Actual: 0
22. Expected: 0, Actual: 0
B3. Expected: 2.9k, Actual: 2.99k
B6. Expected: 2.9k, Actual: 2.97k
RCA left center. Expected: 90k - 115k, Actual: 100k
RCA left ground. Expected: 0, Actual: 0
RCA right center. Expected: 90k - 115k, Actual: 90.8k
RCA right ground. Expected: 0, Actual: 0
Voltages (DC)
1. Expected: 50 - 100, Actual: 78.5
2. Expected: 170, Actual: 177.4
3. Expected: 0, Actual: 0.4
4. Expected: 170, Actual: 177.4
5. Expected: 50 - 100, Actual: 79.3
6. Expected: 0, Actual: 0.4
7. Expected: 90 - 115, Actual: 109.4
8. Expected: 0, Actual: 0.6
9. Expected: 90 - 115, Actual: 106.8
10. Expected: 0, Actual: 0.3
LED's lit? yes
Thanks,
Carl
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Clean the tube pins and let the tubes cook in for a while, like 20-30 hours.
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Second, there is a higher pitched hum/whine/something in the right channel. This noise alternates between a couple higher frequencies. I have found that with this noise, I can tap the side of the larger tube and the noise goes away for maybe up to one second, then comes back.
This is usually indicative of a flaky solder joint.
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Thanks for the suggestions. I will re-solder anything that looks flaky, clean the tube pins, then let them cook for a day or two. If I still have problems, I'll post back with some pictures.
Is there a recommended way to clean tube pins? Isopropyl alcohol maybe?
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https://bottlehead.com/smf/index.php?topic=8888.0 (https://bottlehead.com/smf/index.php?topic=8888.0)
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The pin cleaning method Doc prescribes / relates will no doubt yield steller results. I have to admit that I'm lazy and haven't employed it...yet.
For reasonably good results I plunge the tubes into a new "Magic Erasure" several times, hitting fresh melamine each time. I then apply a tiny amount of a silver-bearing contact lube.
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i know nothing about electrical engineering but can offer my experiences with hums/buzzes coming from the Crack. before installing the speedball, there was always a very very low hum. i am pretty sure it was due to not re-soldering as i should have. but, here's what happened after my speedball upgrade:
here's a recent post about issues that were resolved with my own kit: https://bottlehead.com/smf/index.php?topic=11291.msg102656#msg102656
I'm enjoying the Crack more than ever now - wishing i did the speedball upgrade years ago! tube rolling is next... ;)
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@Neil I have a speedball ready to go. I wanted to get the noise under control before adding it in though.
Oh boy... I re-soldered a few things and now 6 and 10 are at 2.5k ohms. Ugh, I should have just started with cleaning the pins and cooking the tubes...
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Now I'm a little confused. I was searching through the forums to see if anyone else had readings of 2.5k ohms at 6 and 10, and I came across these two posts:
https://bottlehead.com/smf/index.php?topic=5573.0
https://bottlehead.com/smf/index.php?topic=3661.0
Both say that they passed their resistance checks with 6 and 10 at 2.4k ohms. My manual says they should both be at 0 ohms...
If my manual is correct... what would cause 6 and 10 jump to 2.5k on my crack? I did not physically remove any joints, just added a bit more solder here and there where it looked sparse.
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There are changes in the wiring of the headphone jack between versions 1 and 1.1. Perhaps if you have headphones plugged into the jack the values will change from 0 to 2.5k? The jack is a switch type and path to ground from 6 and 10 will by-pass the resistors on the jack when there is nothing plugged in. I hope I have that right.
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There are changes in the wiring of the headphone jack between versions 1 and 1.1. Perhaps if you have headphones plugged into the jack the values will change from 0 to 2.5k? The jack is a switch type and path to ground from 6 and 10 will by-pass the resistors on the jack when there is nothing plugged in. I hope I have that right.
You're absolutely right. I had accidentally left a 1/4" to 3.5mm adapter plugged in to the headphone jack. I removed it and they're both back to 0 ohms. Thank you! Man I feel stupid. At least I can continue working on my original hum problem now ;D
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Ok, here's a quick update on the build.
First, I cooked the tubes between 20-30 hours as suggested. No change in the hums.
Second, I cleaned the pins with metal polish and contact cleaner. They were a lot dirtier than they looked! I used up a lot of q-tips. They can be inserted into the sockets much easier now... But still, no change in the hums.
Now I'm poking around with a chopstick to see if I can pinpoint any joints in particular that could be causing this. So far I haven't found anything, but I'll keep poking around a little more.
Side note: One thing I noticed is that if I put my ear close to the larger tube (after it's warmed up a little), I can hear it making a similar hum to what I'm hearing through my headphones. Is that normal? Should I be able to hear the tube making that kind of noise? I wonder if that's related to the hum I'm hearing in my headphones...
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Ok, I'm a bit frustrated now. I have reflowed all the joints, replaced a wire or two that looked suspicious, and poked and prodded every wire and joint. I even plugged the amp in to different outlets around the apartment just to rule out interference from appliances and other electronic noise. Nothing seems to affect the hum.
Also, for better or worse right now, I installed the small board of the speedball. I was like a kid opening his favorite Christmas toy and I couldn't resist. Installing this has had no affect on the previously mentioned problems. All information I have previously provided is still accurate.
I'm running out of ideas here, so here's some pictures of my build. Please let me know if you have any suggestions!
https://imgur.com/a/MlyDOpU
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I would add a little solder to all the joints on the 6 lug strips where black wires connect. It's possible that the noise you're hearing is from a loose 220uF/250V capacitor, as a loose leg on one of those caps will bring up the power supply noise significantly.
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Not to be too unkind but I'd rate most of your joints as improperly flowed and rather dirty. They should be smooth and with a nice clean appearance. Your iron tip is likely dirty and needs retinning properly. Wind the heat up a bit if it's adjustable or leave the tip on the joint longer. Add additional solder only after the existing solder has steaded to liquify. You may find a flux pen useful. They are very cheap.
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Not to be too unkind but I'd rate most of your joints as improperly flowed and rather dirty. They should be smooth and with a nice clean appearance. Your iron tip is likely dirty and needs retinning properly. Wind the heat up a bit if it's adjustable or leave the tip on the joint longer. Add additional solder only after the existing solder has steaded to liquify. You may find a flux pen useful. They are very cheap.
Please, bring on the criticism! This is my first time doing this kind of project, so there's no doubt places I can improve!
When I reflowed all the joints last night, the joints did get noticeably cleaner/smoother. The pictures were also taken in poor lighting, and it makes the joints look darker than they really are.
I will definitely go over them with more heat and a clean tip when I do as Paul suggested and touch up the 6 lug strip joints. Thank you for the advice.
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Alrighty... I added some more solder on the 6 lug strips and reflowed everything that looked dirty/not smooth with more heat and a clean tip. Hum is still there. I could be wrong, but it seems like this hum is connected to the 6080 tube. Is is possible that the 6080 is bad? Or is there anything else I can try?
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I suppose it's also worth asking what headphones you're using to evaluate this noise.
-PB
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Right... that would be important. Sennheiser HD 6XX from massdrop (300 Ohms)
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You are welcome to try another 6080. There have been several occasions of folks changing out a tube and having a noise go away, only to have it come back later and be tracked down to a problematic solder joint.
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Fair enough. I'll get a couple cheap 6080's off ebay just to satisfy my curiosity. Until then, I guess I'll keep tinkering around. If you can think of anything else, let me know!
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Two suggestions:
(1) Re-do the joints on the rca input center posts - In one photo, the left channel joint looks like a classic cold solder joint. These joints are tricky b/c it's so difficult to get the wire to sit firmly in the solder cup before you apply solder. My approach is to have the open side of the solder cup face away from the direction the wire is coming from, so that the wire end can be bent to grab the inside of the cup and pull against it (subtle manipulations of the wire further upstream can give you that tension).
(2) Double check that the ground tab near the IEC is tight against the chassis.
Good luck!
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Hey so like i mentioned in that thread i linked to you, i had hum for about 4 or 5 years. the speedball upgrade has made it DEAD silent. i mean absolutely completely silent. however, adding a DAC was also very helpful before i did the speedball upgrade since my pc was causing some hum.
the tubes are the originals since i built it.
the hum used to be really annoying.
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Hey so like i mentioned in that thread i linked to you, i had hum for about 4 or 5 years. the speedball upgrade has made it DEAD silent. i mean absolutely completely silent. however, adding a DAC was also very helpful before i did the speedball upgrade since my pc was causing some hum.
the tubes are the originals since i built it.
the hum used to be really annoying.
That's interesting that the hum went away after the speedball upgrade. I was hoping to find the cause of the hum before fully upgrading to the speedball. My computer is definitely super noisy... specifically a ground loop caused by my GPU. I fixed that with an ifi iDefender. But this hum I'm hearing is present even when the crack is disconnected from the rest of my setup.
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I have good news! It was indeed the 6080 tube! I got a couple cheap 6080 tubes off ebay. With both of these tubes, the crack is totally silent. And to confirm, I plugged the original tube back into the crack, and the hum returned.
Just for the record, here's another difference I noticed between the new tubes and the original: With the original, every time I bumped my desk (like with my chair), I could hear it through my headphones in the form of an echo-type sound (the crack is sitting on my desk). Even "little bumps", like just typing on my keyboard. On every key press, that was enough of a "bump" on my desk that I could hear that odd echo sound through my headphones. The new tubes don't do this, which further reinforces my claim that the tube was the problem.
Thank you everyone for your help. I really appreciate it!