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Re: What's in Your tube box?

Posted by Joe Rosen on June 3, 2001 at 08:44:23

In Reply to: Re: What's in Your tube box? posted by Gary Kaufman on June 1, 2001 at 07:02:45:

Trolling for trolls, how droll! Yep, this thread really gets 'em typing, and even I finally had to cave in and post SOMETHING. This thread is almost as bad a troll as the "Your Audio History" in the Vintage forum!
To reply to Gary's question of what oddballs have other folks had good luck with, here are some of my observations:
I have an obscenely large valve collection, as I've been collecting avidly for 20 years. I was buying military surplus quite a few years before it became fashionable, and also lots of cheap Griefkit & Dynacrud when you could buy pieces for $5 to $50 a toss. Heck, when I first started, you could buy H-K Citation II's for $75 in good working condition, a Mac 275 for under a grand and your local tube source couldn't get rid of all his 6LF6's, darn obsolete TV tubes!
As a consequence, I probably have more of any given valve type than the entire collections listed by the posters here, combined!
For example:
Some years ago I bought RCA (the only manufacturer that ever made them, BTW) JAN12AH7GT's. I think I paid about 15 or 20 cents a piece, all NOS in their beige military cartons. Quantity? Oh, a moderate purchase size. ONE THOUSAND. I already had about 70 of them...
After, oh, a dozen years or so, I finally got around to designing something that uses them. A line stage. It sounds very good. I finally compared them to 6SN7's, and they don't seem to sound quite as good, but they are close. It could be that my operating points aren't quite spot on, so I'll fiddle with that and see if I can get improved performance. The other possibility is that the 12AH7's are noticeably more microphonic than the 6SN7, and that this is making the difference. The other could be compatibility with my "test" speakers that used for the comparison, a lowly pair of modified JBL 2800 bookshelf two-ways that I use occasionally as a "dummy load" (that's right, I'm the "dummy", they're the "load"!).
Other oddballs I've had great luck with are 6414's, which I also once designed into a line stage. It has rather too much gain for most systems, and is also very microphonic with a tendency to "sing". I recently incorporated it into one of my amplifier designs as a split-load or "concertina" phase splitter, replacing a type ECC82/12AU7. MUCH better, thank you!
My amplifier uses 6528's as output valves, and these are the finest sounding triodes I've found. FAR superior to junk like 45's and 2A3/6B4 (which I still have several dozen of each type as NOS & UOS, sold off the remaining 50+ I had to some of my Chinese buddies who really go NUTZ for this sort of thing) types. I totally fail to see what all the fuss with DHT's is. Some sound good, some sound pretty lousy! The 45 is a little stinker, and it is seldom used properly since it needs grid current to produce any undistorted power. I think the idea with the SET crowd is NOT to generate any power, and with as much distortion as possible, all the better to mask how lousy the junk they pulled out of the ceiling of the shoe store or the bullhorns at the train stations and racetracks that they think sound so wonderful. I can think of few things more painful than a pair of Altec "Voice of the Bus Station Restroom" that some of the SET lads think are so wonderful...
Not that the 6528 is for everyone either. It is surprisingly analytical, and ruthlessly accurate. But a more powerful and solid clean, clear and utterly transparent triode sound I've not heard. They are also Cetron 300B expensive! They sometimes could be found for $50-100 a pop NIB, and you don't want to buy them surplus, since the power supplies they were designed for just pounded the piss out of them, and there is seldom anything left by the time they get yanked! I once bought 15 of them from a local surplus vendor, and had to return with all them the next day. 14 were dead, the meter on my tester hardly even budged! The 15th was very weak...
I use 6K11/6Q11 triple triodes as the input stage devices in that triode amp, and I think they sound great! All these things are is a compactron version of a 12AX7 and a 6C4 (one half of a 12AU7) in one little water-tower of an envelope, squat little mushrooms with their three little filaments glowing like little fiery pinheads on the top of 'em...Anyways, it saved me one valve socket per channel!
I have also tried 6AQ5's, and loved 'em! These little 7-pin power pentodes are electically identical to the far larger octal 6V6. Whoda thunk they'd sound much the same, too? Actually, they are FAR tougher and sound cleaner and fuller in tone to me than the 6V6 does! Surplus "pulls" yield a survival rate of about 85% or better, and I bought about 1000 of these for 5 cents a pop, as was! I started testing them when I got home, and gave up when so few of them were bad! And this valve has low maximum ratings, and it is so small with so little glass it gets hotter than Hades when run in Class A as is typical of 6V6's! The getter flashing on alot of them look like heck, but they still test strong, are gas-free and sound great! One bullet-proof little bottle! The 811 transmitting triode is badly under-rated by the cognescenti, no doubt because the average valve audio amp designer is a compleat dithering idiot with the ego of Napoleon Bonaparte (hey! don't look at me!). The 811 requires someone with real brains and some patience, but can reward you with fabulous DHT sound and STUPID power, AND with good specs! A pair can pump out an easy 175 Watts, and the excellent sounding Ryazan 811's used to be WAY better built and sounding than the NOS 811's they replaced (in my Altec 1570B's), and were only $16 a pair!!!! Sadly, Ryazan is shut down, so you'll have to use Chinese garbage instead. Although I think Svetlana offers an 811...hmmm, I wonder where IT is made! The Svet is only somewhat more expensive, so relatively cheap. And the Russians seem to have the Zirconium anode types figured out pretty well for the sonics, too bad about the nickel/steel receiving types that sound uniformly miserable!
I have also tried plenty of oddballs that sounded horrid, though.
I once tried a 6S4 as a replacement for an EL84/6BQ5 in my second SE amp that I built in the mid '80s, and this was a disaster! The sound was a spongey mush...Ditto an attempt to use a type 6CK4 for a push-pull amp. I ended up with a "mush-dull" amp, instead! Truly dreadful, and I noted that Victor Khomenko had very nice things to say about it in one of his posts. Then again, I don't agree much on issues of sound quality and design philosophy with the good Mr. Khomenko, so the watch-words here can be abbreviated to: YMMV!
Other successes: Before I moved to the 6528, my amp had been using type 7236 Dual-Triodes. A lovely sound, very pretty!!! Very slightly soft compared to the 6528, and the failure mode was Siemens 6922/7308-like. A crisp, lively, open and airy sound when new, then slowly getting fatter & duller until audible transient distortions start creeping in (a progression of the fat/dull thing, which is actually a subtle "blurring" that gets worse until it becomes a clearly audible transient distortion artifact. I suspect increasing grid emissions due to cathode material migration is the problem here...). Still, I got about 3 years out of a set before the distortion would get bad enough to really bother me, and I bought 900 of those at about $2.00 each a few years ago...
The amp used 6BX7's before THAT, when I first designed it in 1988. They sounded great, too. As did the 6BL7 when I tried it, and the 6AS7/6080 had a gorgeous tone, too. But the latter has such low gain that the drive requirements are immense, and a good design is hard to implement without a beefy, very high-voltage driver stage. I designed and built my own derivatives of the Dickie/Mackovski all-triode OTL (the design is marginally pre-Futterman, 1953. Dickie & Macovski were RCA engineers, and the design was occasionally referred to as the "RCA OTL" instead, since Mr. Mackovski has one of those "difficult" names!). This amp, when I designed the miserable ECC81/12AT7's out of it, came good and sounded leagues better than a Futterman (and I own a couple of those, too!).
Other good oddballs: 6CZ5 is good, but if you can find NOS 6BQ5's, why bother? 5963's can be substituted for 12AU7's, and sound pretty good. But they are considerably more microphonic, so again, why bother? 7062's (ECC180CC) are also very good sounding, but are hideously microphonic! Fine in a power amp with feedback though, if you need a duo-triode with a mu of 50...A 6211 is a very nice sounding valve, very similar to 12AU7's in tone, but noticeably higher gain (mu of 31). Again, this is a computer valve and is quite microphonic. I have about 6000 of these...Still trying to figure out a satisfactory application for it! 5965's are a crisp, clear sounding valve with little if any listening fatigue when used sympathetically.
Also a microphonic computer valve, and like the 6211, very long life!
The 5965 is more 12AX7-like in tone, more 5751-like even. The vendor who sold me these was "white boxing" them and selling them off as 12AX7's!! Apparently, guys who were restoring old electronic organs, with their banks of 12AX7's, were quite happy with this sub...
I think I've got about 4000 of those...Again, no application for them as of yet...
Then there are the "potential" application subs, and the "interesting" valves that I haven't had the time to fiddle with yet. These include subbing 12AX7's for 6SQ7, 6CN7, 6/12AT6, 3/4/6/12AV6 and 6AQ7. Oh, and 6112! Then there are the 12AU7 subs, I've already tried the 6211, 6414, 6350, 6GU7/12BH7, 12AH7, and 6BL7/6BX7. But I still haven't tried my 6111's, 6SR7's, numerous compactrons like 6AV11 & 6B10, or Button-9-pins like 6BJ8 or the triode half of something like a 6BL8...
For 6DJ8 subs, I have substantial quantities of 5670/2C51, 6J6, 5/6BK7, 4/6BZ7/BQ7 and 4/5/6BS8!

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