Noisy original tube [resolved]

klaseck · 486

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Offline klaseck

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on: July 04, 2020, 06:05:30 PM
The Crack I built earlier this year has always had a faint but audible humming, regardless of the volume setting. After replacing the original General Electric 6AS7 GA power tube with a Sovtek 6AS7G the noice finally disappeared! It is now dead silent up to maybe 90 % volume when there is no input signal. I also find the sound even better, a bit warmer and fuller. My love for the Crack is now complete!

Was my problem simply a noisy GE tube? If so, can I get a replacement?
« Last Edit: August 04, 2020, 05:45:01 AM by Paul Birkeland »


Offline Paul Birkeland

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Reply #1 on: July 04, 2020, 06:14:04 PM
The big issue with requests like these, is often we find people will come back later to let us know that now the new tube is also noisy, and then we can help diagnose what's actually going on in the amp. This isn't always the case, but certainly more than half the time!  Here is a thread from just a few days ago that is a pretty typical example.   When tubes are removed and installed, wires and other connections move around, so what may seem like a resolution with a new tube can end up simply being the amp reacting to physical movement. 

Still, you could e-mail replacementparts(at)bottlehead(dot)com to see about shipping the tube back for exchange. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Deluk

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Reply #2 on: July 05, 2020, 02:54:31 AM
Most amps, and I expect valve amps would be worse than transistor ones, are likely to produce a bit of hum at 90% volume settings. Might be a bit of hiss too. It's highly unlikely you'll be using yours at anywhere approaching this level so I'd say that it's irrelevant. Doesn't mean that you shouldn't check for poor connections and possible ground loops though.
« Last Edit: July 06, 2020, 02:01:33 AM by Deluk »


Offline Paul Birkeland

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Reply #3 on: July 05, 2020, 05:06:45 AM
Oh,  I didn't even notice that tidbit.

Yes, that's completely normal to have some noise with the volume pot all the way open.  This is mentioned in Crack FAQ #5:
https://forum.bottlehead.com/index.php?topic=4295.0

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline klaseck

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Reply #4 on: July 06, 2020, 10:40:31 AM
As I wrote, the noise with the original tube is constant, regardless of volume setting. I have taken it out and in many times, without any change. With the new tube, the Crack is dead silent until I raise the volume way up. So I am pretty confident that the problem lies with the tube as such. I will try to get a replacement.


Offline klaseck

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Reply #5 on: August 03, 2020, 07:17:23 PM
Just got a replacement tube today - an RCA instead of the original GE - and this one is dead silent, and plays very well. Perhaps a bit softer base than the big Sovtek 6AS7G tube I bought, but clear and relaxing.

Thank you; I am more than pleased by the service!


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