Uber quiet tubes for C2300 pre

All the NOS tubes I've tried from UA (maybe a dozen or so) have been weak and overpriced! And their remarks about 5751 are incorrect from an audiophile POV. (Might apply to guitar players overdriving their amps to get that "fuzzy" sound they like.)

Regarding the "fact" that 5751's have 70% the gain of 12AX7's: First of all, 5751's were initially designed for military use (the 3-mica version, anyway) and the Air Force wasn't going sub tubes which couldn't PERFORM the same as regular 12AX7's. Second, most circuit designers would never ask any tube to operate in the range (top of the curve) where that extra 30% would be a factor; and third, the best examples of 5751's (like the RCA's and Sylvania's I mentioned earlier,) if really new old stock, or almost new old stock, have transconductance readings way above the "average normal". The AN for a 12AX7/5751, for example is 1250 micromhos. All my good ones read 1300 (minimum) and most are 1500 +/-. So I wouldn't let the 70% thing bother you if you're buying premium NOS 5751's (but don't buy them from UA ;-) I also caution against buying really 'brand new' (never used) vintage tubes. You could be spending a lot of money for something that pops the first time you power it up. I have purchased truly NOS tubes, but insist the seller run them in a piece of equipment for an hour before shipping them to me ;--)

For those unfamiliar with "Joe's Tube Lore", this rundown on 9-pin twin triodes, is highly recommended as a place to get your feet wet. It's where I started, and a good guide to future exploration: http://www.audioasylum.com/scripts/d.pl?audio/faq/joes-tubes.html

Joe's Tube Lore is a great place to start learning about tubes in general. I have several of the tubes he has referenced, especially 5751's.

I'd like nothing more than to use some of the 5751 tubes I have lying around. Maybe I'll give them a try anyway.

I agree about UA. I've bought from them twice, but not a third time, no way.

I've only purchased power tubes from Upscale(NOS and new production, over the past 12 years), and have had nothing but good experiences and performance. Never small signal tubes, so- no comment there. I HAVE BEEN purchasing NOS small signal tubes(Mullards, Teles, Siemens, etc, from the 40's through the early 60's) for decades, and HAVE NEVER had one go south, even after years of use. I'm simply careful, regarding from whom I buy them. Whatever you choose to do(Cajunpepe), don't pass up listening to the Tele ECC83 smooth plates, at least.