[dstarr3]

In the chance that, hopefully, someone might have an idea of what I could try, I'm going to explain my issue and what I have tried in the past months.
My kit had been working perfectly fine for a couple of months, until suddenly it started having a noise issue on the right channel that with time became worse.
-The issue: it's a crackling/static noise that appears exclusively in the right channel, about 10 seconds after I power on my kit. It varies in intensity seemingly randomly, at times it's louder and at times it's quieter. Here's a recording of it. The noise appears with and without a source connected to the amp (simply plugging it into a wall outlet and plugging in headphones is enough). Changing the volume with the potentiometer does not affect it in any way. RCA's being connected or not doesn't matter.
-What I have tried: I extensively chopstick tested to find any weak connection in my solder joints, and reflowed every single joint in the amplifier. I have switched around many tubes that I know worked perfectly. I have replaced the potentiometer. I have replaced the octagonal tube socket with one that makes better contact. I made sure each tube I try has clin pins and a good contact. I have added the reccommended modification with two diodes at the ground tab (it got rid of noises coming from my noisy pc). I have tried different headphones and cables. Different power cords and wall outlets. I have moved to different places of my house and different houses altogether to get rid of possible radio/wifi signals (I even tried placing my amp inside a microwave).
-The most bizzarre part: I have brought my kit to two different repairman places, on two different occasions. In both cases my amp worked flawlessly at their place (in one of the two occasions I have listened to it with my own ears and there was no noise). Upon taking my amp back home, the noise appears again.
That is when, as I said previously, I tried every wall outlet in my house, made sure there was no signal interference and brought my kit at about 4 different places to test. The noise was always there. I have made sure that my houses grounding works fine, and that I wired my transformer for 245V, which is what I read from my outlets.
As of now I am at a complete loss. I can't for the life of me figure out what could be possibly causing this, and why the issue disappears whenever I bring my kit to a professional.
If you have any thoughts or ideas about what I could do, please tell me. I just want to listen to my amp again

It might just be one of the tubes. Maybe one of the pins is corroded and the jiggling in transit is what makes it sound fine for repair folk. A good thorough cleaning of the pins and sockets might be all you need.

Another option is plugging everything into an Uninterruptable Power Supply (UPS) instead of directly into outlets. That should eliminate any possibility of dirty power.

 

[Beefy]

I had looked into that and found contrasting opinions, but I'll stop doing that. Thanks for the advice.
The noise is constant. The only moment it leaves is when I turn the amp off.

Not for the Crack, there should not be contrasting opinions. Never leave phones in during power on or switch off.

Have you tried shielding your tubes? A steel cover or aluminium foil tent just to see. I could hear WiFi beacons through my Crack with many different input tubes, and a tube shield fixed it completely.

 

[Cowwe]

It might just be one of the tubes. Maybe one of the pins is corroded and the jiggling in transit is what makes it sound fine for repair folk. A good thorough cleaning of the pins and sockets might be all you need.

Another option is plugging everything into an Uninterruptable Power Supply (UPS) instead of directly into outlets. That should eliminate any possibility of dirty power.

Unfortunately, as I mentioned before, I have already tried a number of different tube combinations and cleaned each tube's contacts. I thought I might have dirty or bad connections on the octagonal socket, so I replaced that altogether. Nothing ever changed.
I have also plugged it to my UPS running on its own batteries, and the noise remained.

 

[Cowwe]

Not for the Crack, there should not be contrasting opinions. Never leave phones in during power on or switch off.

Have you tried shielding your tubes? A steel cover or aluminium foil tent just to see. I could hear WiFi beacons through my Crack with many different input tubes, and a tube shield fixed it completely.

I have not tried aluminium foil, but I have tested my amp in a house that has no wifi beacons for hundreds of meters and the noise was unchanged. I also tried placing my amp inside of a closed microwave, which should shield well, but that had no effect on the noise either.

 

[DenverW]

If the amp worked without noise at different places, such as the repair shop, I would identify what is different from the shop vs your home. That should help identify the issue. Things that didn’t change between your home and the shops, such as tubes, could be put aside for now.

 

[Beefy]

I have not tried aluminium foil, but I have tested my amp in a house that has no wifi beacons for hundreds of meters and the noise was unchanged. I also tried placing my amp inside of a closed microwave, which should shield well, but that had no effect on the noise either.

Yeah, I found your thread on the Bottlehead forum. You're more patient than me; I would have set a great big bonfire by now, and moved onto more productive things.

Back in the day, I always used to tell people don't DIY if you aren't willing to throw away the entire purchase price. And that advice still holds now. There's either something really sill you're missing, or this whole DIY thing just isn't for you. How much is your time worth?

 

[mformoriarty]

Not for the Crack, there should not be contrasting opinions. Never leave phones in during power on or switch off.

TIL. Didn't know it could cause issues but your logic makes sense. I sometimes leave the phones connected when swittching off but never when turning on, will definitely keep it in mind for next time.

 

[Cowwe]

Yeah, I found your thread on the Bottlehead forum. You're more patient than me; I would have set a great big bonfire by now, and moved onto more productive things.

Back in the day, I always used to tell people don't DIY if you aren't willing to throw away the entire purchase price. And that advice still holds now. There's either something really sill you're missing, or this whole DIY thing just isn't for you. How much is your time worth?

I have indeed felt the urge to open my window and throw my amp very far into the garden on multiple occasions, but I just couldn't. I have to find a fix to this, one way or the other.
Even if I gave up and decided to spend my life savings on the best amplifier I could purchase, I wouldn't be able to let my Crack sit there broken. The amount of hours I spent on it just reinforce my will to look for a solution.
As you said, the biggest likelyhood is me missing something very silly, which is why I'm trying to look for other levelheaded people's opinions.

 

[Beefy]

TIL. Didn't know it could cause issues but your logic makes sense. I sometimes leave the phones connected when swittching off but never when turning on, will definitely keep it in mind for next time.

Check it with a multimeter. It depends on your caps and tubes, but I see a 9-12VDC spike on both power on and power off.

 

[FlatCap72]

I have indeed felt the urge to open my window and throw my amp very far into the garden on multiple occasions, but I just couldn't. I have to find a fix to this, one way or the other.
Even if I gave up and decided to spend my life savings on the best amplifier I could purchase, I wouldn't be able to let my Crack sit there broken. The amount of hours I spent on it just reinforce my will to look for a solution.
As you said, the biggest likelyhood is me missing something very silly, which is why I'm trying to look for other levelheaded people's opinions.

Apologies if this has already been suggested to you, but have you checked your circuit for any wires pressed against each other? The recording you provided sounds eerily similar to the noise my kit was giving off around a year ago. It was only after gently separating two touching wires that it disappeared for good.

 

[Cowwe]

Apologies if this has already been suggested to you, but have you checked your circuit for any wires pressed against each other? The recording you provided sounds eerily similar to the noise my kit was giving off around a year ago. It was only after gently separating two touching wires that it disappeared for good.

Unfortunately yes. I have spent a good number of hours going over every and each wire and connection in my kit, and after fixing a couple of sketchy looking joints everything looks orderly.

 

[DenverW]

Unfortunately yes. I have spent a good number of hours going over every and each wire and connection in my kit, and after fixing a couple of sketchy looking joints everything looks orderly.

So, I want to revisit when you mentioned that two different repair shops did NOT have the issue when using the amp, and you heard this yourself at one. Wiring, joints, tubes, etc will all have been the same at those shops, right? So, what is different at the shop? If it were just something shifting during travel it wouldn't be only those shops, but the other locations you've tried the amp, so I don't find that to be likely.

Did they use a different power cable? Did they use different power strips or power conditioners; basically is there something different with the power there? Anything different? If you can do a 100% like to like test where you're using everything the same (headphones, tubes, power cord, amp) and there is no crackling THERE but there is at your home...the issue is most likely outside the amp and is location based. Power is a possible culprit. You mentioned you went to another home and tried things; how close was this place to yours?

I'd investigate this a bit; perhaps speak with the repair shops to see if they have any power conditioners or some such.

 

[Cowwe]

So, I want to revisit when you mentioned that two different repair shops did NOT have the issue when using the amp, and you heard this yourself at one. Wiring, joints, tubes, etc will all have been the same at those shops, right? So, what is different at the shop? If it were just something shifting during travel it wouldn't be only those shops, but the other locations you've tried the amp, so I don't find that to be likely.

Did they use a different power cable? Did they use different power strips or power conditioners; basically is there something different with the power there? Anything different? If you can do a 100% like to like test where you're using everything the same (headphones, tubes, power cord, amp) and there is no crackling THERE but there is at your home...the issue is most likely outside the amp and is location based. Power is a possible culprit. You mentioned you went to another home and tried things; how close was this place to yours?

I'd investigate this a bit; perhaps speak with the repair shops to see if they have any power conditioners or some such.

This is definitely something I mean to investigate, being by far the strangest thing about my situation. I had planned to bring my amp back to one of the two places yesterday, to make sure with the repairman that we were using the same gear (I only know for a fact that he was using my tubes and power cable), but work wouldn't allow me to.
Distance wise, the first repairman I brought my kit to is about 15 kilometers away from where I live. The second 45 kilometers away.
The places I brought it to test were respectively 5km away (I had brought my kit here before, back when it had no issues), 3km away, and one place that's barely 1km away from the first repairman I mentioned.

 

[michael2v]

The amount of hours I spent on it just reinforce my will to look for a solution.

Don’t fall prey to the sunk cost fallacy (those hours are already gone), but only work on it as a labor of love!

 

[markkr]

I had looked into that and found contrasting opinions, but I'll stop doing that. Thanks for the advice.
The noise is constant. The only moment it leaves is when I turn the amp off.

Not ideal but have you reached out to Bottlehead regarding their repair service?