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6SL7

Posted by Laudanum on April 12, 2017 at 05:14:23:
Hi all.
I have 4 6SL7 tubes that I keep on hand for the preamp of a Valco style SE guitar amp. I know they have a reputation for being microphonic, and they all are, except for 1. I have a CBS Hytron which is the only one of the bunch that isn't microphonic. Two of the tubes are JAN tubes, both Sylvanias I think. And the other is an RCA. All 3 of the microphonic tubes have the longer plates. The CBS Hytron is a short plate tube.

To get to my question ... in general, is there a better chance that the short plate 6SL7's wont be microphonic? I picked up a short plate, brown base Sylvania WGT on ebay just to test the theory. But it was cheap and eabay is a crap shoot. If it works, great. But I'm wondering if there are any generalizations that can be made regarding the plate type/length and microphonics?

Also, ran across quite a few GE chrome plate tubes that had large but shortish plates that looked like they may be less prone to microphonics. But that's just a wild guess.

As far as tone goes, it really doesn't matter much in this amp. They all sound a little different but the amp isn't played clean and they all seem to do the overdrive just fine so I'm not after the tubes with the best reputation for tone nor the price they demand. Just hoping to find a couple inexpensive spares that aren't super microphonic.

Thanks for any advice you can share.