Buzz/jingle in left channel. goes away when tilted

[keithpgdrb]

Hey all,

new crack owner and first post on the forums.  I've got a buzz/jingle type noise in the left channel of my amp.  noise gets worse if I tap the power tube.  goes away if I raise the right side of the amp by about an inch.  bad/damaged power tube?  I cant think of anything else that would be effected by tilting the amp.  when its tilted, its silent.

any help would be appreciated.

[Doc B.]

Could well be the tube, but if a 120Hz buzz it could also be an intermittent ground connection that is being put into better contact by tilting or flexing the chassis a bit. Visually inspect your solder connections up close and if they look good try letting it cook in for a few hours and see if the problem reduces.

[keithpgdrb]

I'll give it the once over and let er cook.  see what happens.  thank you for your help thus far.

[keithpgdrb]

letting it cook for a bit now.  upon power up, volume at 0, you can hear the tube heating up.  little pings and rings, then the crackle sound develops in the left channel.  possibly the right, but its pretty hard to hear.  I'll report back after a few hours.

[Doc B.]

If it's more of a crackle than a steady 120Hz buzz, it's the tube. Is this a just completed build, or a used amp?

[keithpgdrb]

If it's more of a crackle than a steady 120Hz buzz, it's the tube. Is this a just completed build, or a used amp?

I would say it definitely sounds crackly in the left, especially when the noise first starts. The sound in the right channel has kind of a "jingle bell" sound.  The noise does get quieter the longer the amp is on, and sometimes disappears., but it comes back for no reason.

I am still going to double check all the solder joints, but It sounds like a tube thing to me.  power tube specifically I think.

Unfortunately the amp is used so I wont benefit from any kind of warranty I know.  I'll take a look at the tubes and see whats in there.  maybe you have replacements.

[Laudanum]

I've had something that seems similiar happen with a 5998 tube.   Almost sounded like a static and arcing sound, audible coming from the tube itself on start up and that coincided with a visible white flash on the filament between one of the plates on start up.  The white flash was less intense and intermittent but still visible after the tube warmed up.  When listening with phones,  a static/crackle sound in the left channel followed the intermittent white flashes visible in the tube.   I didnt try tilting the amp, I knew it was a problem tube.  Especially being an OTL amp, I didnt mess around with it much and swapped in another tube.   Im not saying it's definitely the tube in your case, just that what you describe sounds similiar and in my case it was the tube.

[keithpgdrb]

The power tube is a Jan 6080WC Sylvania - little guy is an EH 12au7a.  both in expensive tubes as far as I can see.  I'll be checking the solder joints today and taking some measurements to see if anything is amiss on that front.

fired it up just now to check it out.  I can hear the noises coming from the power tube itself with no headphones on.  its definitely the power tube. 

I know there are lots of options here via the rolling thread, but what is a good sounding replacement?  what is the stock option?

[adamct]

Keith,

Just a reminder...don't solder the tube socket pins with a tube installed.

There isn't really a stock power tube, I don't think. It's just whatever the Bottlehead team can get their hands on. Lots of people like the RCA 6AS7Gs, which are fairly inexpensive. The Tung-Sol 5998 is a popular "upgrade". Frankly, there are lots of options, and I haven't found a tube yet that didn't sound good in the Crack.

Best regards,
Adam

[keithpgdrb]

Thanks for the replies and suggestions.  I'm going to keep it simple and just have bottlehead send me a power tube.  I can change it out later if need be.  They said they are sending a 6080.  that should solve the problem.  if not, well, not a big loss, but it should.

[adamct]

I actually prefer the 6080s. I think they are slightly more robust in their build/design.

Best regards,
Adam

[Laudanum]

I think the 6080's tend to be less microphonic.   I also agree for the most part in that there really isnt a tube that I have tried that didnt sound good with this amp with the exception of my not being wild about the RCA cleartops or the Russian 6H13C. 

[lachlanralph]

Hi Guys, did the replacement tube fix this? I think i have the exact same issue, a whine in the left channel that goes away when the amp is tilted up on the right(so the right side is higher that the left) it seems to be quite high pitched definitely not 50Hz. changing the volume position does not seem to affect the sound at all.

Thanks

Lachlan

[keithpgdrb]

I was taking some measurements before I get the new tube installed.  I dont understand the measurement between 12 and 13.  my measurements start at like 4Mohms and come down.  slowly..  sup?

also, where is the center pin measurement?  is it the center pin of the 12au7a socket?

[keithpgdrb]

Hi Guys, did the replacement tube fix this? I think i have the exact same issue, a whine in the left channel that goes away when the amp is tilted up on the right(so the right side is higher that the left) it seems to be quite high pitched definitely not 50Hz. changing the volume position does not seem to affect the sound at all.

Thanks

Lachlan

I'll let you know.