12AX7 Tube MP Shoot-Out

E

Emeric

New member
Well not really.

I took apart the tube mp tonight. This is an extremely unscientific test. I recorded 3 takes of a Guild acoustic, and 3 takes of vocals through some Canare wire into the MP out of the MP through Canare wire into an Aark 20/20.

I left the gain the same on all takes. I normalized all vocals to -4dB.

The Tubes:

- Westinghouse 12AX7A - 1960's, brand new.
- General Electric 12AT7WA - July/65, brand new.
- Original Sovtek 12AX7A that was in the ART

Each tube was allowed to warm up for 10 minutes (I don't have all night).


I found very subtle differences in gain between the different tubes (again this could very well be due to how I was playing the guitar or speaking... I tried my best to be consistent, but this is not easy.)

The loudest of the bunch appears to be the Westinghouse, 2nd was the Sovtek, 3rd the GE.

As far as sound quality. Very difficult to judge. I liked the GE the best (and I can't explain why at this point. too subjective) and left it in the unit for now until further real application testing.

An interesting thing I found about the GE, it gets warmed up almost instantly, and glows much brighter than the rest... hehhe.. not that this matters - but it looks cool, hopefully it wont burn up when surrounded by the casing.

The ART I found a real curse to put back together again... I had to cut the piece of foam that holds the circuit board with all the buttons/knobs on it in half to reassemble it.


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I made mp3's of all these files, but I don't think they are worth judging anything from. There is much more I should put into this, but I need to do this sometime under controlled circumstances. A sound source that won't move for one, and be able to play identical.

Final word - I don't think there is a hell of lot of difference, but If I find there is, I'll let you know.
 
I am interested to know...

What order did you test the tubes in? Which was first and which was last?

Ed
 
First was the GE, Last was the Sovtech. But my results are very inconclusive. I'll do some more practical recording and see what happens. I also tried a Phillips and Sylvania, But messed up the wav.

I should really record a constant source, this would make for a better comparison.
 
Just checking...

Because Emeric only let each tube warm up for about 10 mins,I was thinking that the results could be colored from the heat buildup in the box. It is no secret that the ART unit needs to be on for at least a few hours before it sounds right. I think it needs to be on for a few days before it starts to sound right....:)

Emeric, please at least give each tube 4 hours to warm up, and I would trust your results that much more.

Also, try micing a speaker cabinet with a distorted electric guitar. Or, mic a home stereo speaker that has a CD playing through it. This way, you are pretty much assured that the source sound is consistent.

Ed
 
I would guess that using different tubes would give you really subtle differences in sound. I've had friends change all 6 or 7 of their tubes in guitar amps and pay a lot of money on expensive, hard-to-find tubes only to notice minor changes in tone. Maybe if you are used to really cranking the gain on the TubeMP then you might notice a difference. I never thought of letting my BlueTube warm up, thanks for the advice Sonusman. I wonder how often one should change the tubes in these pre's. I know that when I do I will use the same brand/spec tube that it came with. I'm sure the companies optimize the product's performance with a specific tube, even if it's a low cost one.
 
I Don't Know...

But I notice quite a significant different when changing tubes in my tube mics. I can get more specific if needed.

I can't wait till Sovtek releases their 6072/12AY7. It's coming soon!
 
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