Not all, but most of the tubes you see in this picture of the Eniac computer, from 1946, are 6SN7s.

http://explorepahistory.com/kora/fil...h7g3-a_349.jpg

Output Tube Shootout!

Amp: Inspire KT88 SE HO, the one with 20 watt output transformers and which can produce 17 watts with KT88 and 5AR4. Tested with Westinghouse 6SN7GTB and Sylvania 5U4G.

I decided to put many of my output tubes to the test. System setup: Sony SACD player, Parasound D/AC-1100HD, Dynaco PAS-4 preamp (the 1990s version, with 6DJ8 line stage tubes - I'm using Amperex JAN 7308 in it), Focal Aria 906 monitors - efficiency around 88db. This is my small system, it will be a few months until I get my primary set up, as I'm moving. The sound presentation from this system is quite nice, throwing up a reasonably large soundstage, good detail on highs (when there is too much detail it is immediately apparent), a warmish full sound through the mid-bass falling off in the mid-40s, so nothing too deep and as it is a bit warm in the mid-bass it is also immediately apparent when a tube is a bit forward or loose there. My big Von Schweikert towers (now packed in a box) are cleaner and deeper and would be more revealing.

I like tube components in my small, monitor system, as they add to the magic and romance of a simple two-way bookshelf setup.

Music used: Norah Jones and Holly Cole. Simple arrangements with piano, string bass, and brushed cymbals. Very clean recordings.

Tubes being compared: Gold Lion KT88 (new issue), Gold Lion KT66 (new issue), JJ KT77, Sylvania fat boy 6CA7, vintage Tung-sol brown-base 5881, Sylvania 6V6GT, Ken-Rad black glass 6V6GT

The two sets of 6V6 tubes sounded very similar.

Best defined bass: KT66, 2nd place: KT88

Best high freq detail without being too much: KT77, 2nd place KT88, KT66

Best natural vocals: All were pretty good. KT77 maybe best with the KT66 & KT88 just behind. 6V6 was attention-grabbing with its female vocals being a little forward.

Smoothest overall sound: 6CA7 - perhaps a bit too smooth. Bass was a little ill-defined, highs not as tinkling, but a very relaxing presentation. I would say that these along with the 5881s produce the most classic "tubey" sound. Very different than the 6V6, which was more aggressive through the upper midrange.

Tightest sound with best imaging: KT66, 2nd place KT88. The 6V6s threw up a very good soundstage too, but a little looser in the bass.

Hard to say which is the best overall, as all sounded good and all had their strengths. Picking a best might depend upon my mood at the time and the music being used. If I were using my Spica TC60 speakers with their slightly softer highs, I might lean to the 6V6. The 6CA7 and 5881 are very listenable and when relaxing in a dark room, late at night, they would be excellent. Perhaps the best all-around tube with no weaknesses is the KT88, but I wouldn't rank it first in any category. For a dynamic, tight sound, I like the KT66. And for something which is good on definition & dynamics but a bit sexier on vocals, I'd be happy with the KT77.

I can't say there is any tube I tested which I would never use. Two favorites right now are the KT66 & KT88.

Would have loved to have a pair of KT150s to throw in the mix. A little pricey when one isn't sure they would make the main rotation. A nice pair of standard 6L6CG would have been good to compare too. And 6550s. And ... :)

Yep! Tungsol 6SL7

BTW, great tube-rolling work there, pal. Thanks for the very valuable information. I agree on your takes on the 6V6's and KT-88's. I guess having the KT-66 you really won't be needing the 6L6 CG.

You all are tube rolling junkies.:D

I have yet to get through more than the following in terms of rolling and I've had my KT88 HO amp for exactly 1 year -

Power Tubes: GL KT88, RCA BP JAN 807(w/adapter), TS KT120, TS 6L6G(C), GL KT77, TS 6AR6(w/adapter)

Driver: RCA BP 6SN7, RCA BP 6SL7, Syl Chrome Dome(s) 6SL7GT & 6SN7GT, RCA BP VT 229

Rectifier: Mullard 5AR4, RCA 5U4G, Type 80 (w/adapter), RCA 5U4GB

I haven't even gotten to the NOS 6550's, EL34's, 6V6's, & KT66's yet. It will take me years to roll through all the combos I have. I like to listen for a couple of months before I make a change as they all sound so good.(Except the 6AR6, hated them, but think they weren't good tubes)

I will say that I use a sub for anything below 100hz and I think that eliminates an area where most of the power tube rolling is most evident. The differences then are soundstage and HF performance and that is where the drivers show their strengths and weaknesses.

Additionally, I've tried several preamps with the Inspire Amp: McIntosh C46, Bryston BP25, and an LP-27a. The LP-27a is the winner with that amp... and also with a quad of MC30's as well as a pair of monobloc MC240's. I haven't tried it with the Heath UA-2's that I have yet, but I have no doubt it will make them sing. It's an exceptional piece of gear.

I have one more recently acquired preamp that I have yet to try - a McIntosh C100-A. I haven't even set it up yet. I have a feeling the LP-27a will better it, though.

Yup, you can go nuts rolling tubes in these amps. I've had my combo a little more than a year and some power tubes are better than others. It takes listening time to get to know what works best in your rig.

For you LP27a dudes Tube World Express has British Tungsram Type 80 NOS/NIB rectifiers for $25. Very good tubes. Put one in your pre and be done. :thumbsup:

I have so many rectifiers of all types - in 80's I have Globes & ST's from Cunningham, Sylvania, RCA, Philco, GE, etc. I don't think I'll be buying any more - or Power tubes or preamp tubes. Pretty much set for life in tubeland. Actually going to start divesting soon.

Thanks for the tip on Tube World Express and the 80 rectifier. I only have two for my LP27a, a National Union it came with, and a Cunningham from flea bay sold as NOS/NIB. It doesn't look new to me, base is a little loose, not sure if a new tube would have a base that turns slightly.

I sent my 27a back to Dennis to replace the volume pot with a DACT. He recommended another upgrade which I said yes to. I don't know the cost and don't care, this gear sounds so good and is so much fun:

"it makes little engineering sense but … I just completed an LP-27a this afternoon with the stepped DACT attenuator and my wife noticed a change in the sound immediately as I did as well. What the heck ….. I also put in very special silver output coupling caps along with a second filter choke in the regulated power supply. I would recommend you upgrade all the way with these parts as well."

Yeah! and apparently you are a components-rolling junkie!:music:

Some tubes do have a loose base, even if new. But it can very difficult to impossible to tell a used tube from a new tube. Sometimes it doesn't matter much. A small signal tube can last 5,000+ hours. If someone put 200 hours on it, then that doesn't make much difference.

I need one of those ... :sigh: