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Old 28th May 2002, 04:08 AM   #1
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Default What tubes are best for preamp?

I am in the market for a new preamp and wondered if there is a "tube of choice" for use in a phono and line level preamplifier.
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Old 30th May 2002, 09:44 PM   #2
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Default TOOBES!!!!!

Am I going to have to drive up there and straighten you out? Actually, I have a phono preamp laying around up there already. Has balanced inputs and it set up for moving coils.

Jocko
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Old 30th May 2002, 10:38 PM   #3
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Search the web for "Thorsten AND Loesch AND RIAA" and you will be rewarded. I think he calls it Toccata. There may be something on TNT audio as well.

Petter
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Old 30th May 2002, 11:51 PM   #4
dice45 is offline dice45  Germany
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ronjg,

sigh, what do you want ot achieve with which stage? According to that you have to choose the appropriate tube.

And it highly dedpends on design philosophy.

Do you want to have tubey sound?
Do you need low output impedance?
Do you want to drive chokes and transformers or would you prefer to go with RC-coupling between the stages?
Single-ended stages or differential?
Active or passive phono EQ?

How do yo intend to solve the MC headamp problem? buy $$$ input transformers or build an active SS headamp?

Maybe the preamp Jocko is suggesting is not a bad choice at all if you faces looks blank at my QQ .

Aint that easy w/o knowing where to go.

At the moment, i am musing about my own preamp, i am going the juicy, high-current path with chokes or transformers as anode loads, all stages differential and as much DC-coupling as possible. 2x EC8010 in the fist stage and 2x 12B4A in the 3rd one. And i haven't settled yet which tube to use in the second amp stage, means, i haven't yet found a single triode having enough transconductance at ”=20; up to now i hope i seek out some 5687 or 6900 samples (double triode) matched well-enuff internally for my purposes. 12A4? maybe. Anyone got a data sheet? And then, if tube choice fits my technical requirements, does that guarantee the amp sings? No, not at all.

Having said that, a 5687 or 6900 driving a Shilton pa102 output transformer makes one gorgeous piece of a single-ended linestage. For phono, well, 12AX7/ECC83 can do fine, will sound tubey, will not enthuse to drive passive EQ or trannies at all. Bathe in beauty (and drown in it) but again, depends on circuitry. Or you go with Ratheon 5842 with is juicy, fast, lean, mean, not-tubey, high-current, fairly close to my choice (but stay away from WE 417A, take Raythoen 5842 althiough it seems to be the same tube. In this case the highly reputed 417A is too microphonic).

Or you go with Allen Wright's style who does it all with 6DJ8 and cascodes and superdupercathodefollowers. Gorgeous HiFi. Aint cheap, can be had as kit.
www.vacuumstate.com

Just musing. So much options. (sigh)

I would have to know more about what you want before i could give seriousrecommendations. And i hope other forum members with more practical experience join us here. I am more a designer mind than a tryout one
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Old 30th May 2002, 11:55 PM   #5
PassFan is offline PassFan  United States
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www.borbely.com has a tube phono for mm or mc.
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Old 31st May 2002, 12:29 AM   #6
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The most common tubes for such things:
6DJ8 (aka 6922)
12AX7 (aka 7025)
12AT7
12AU7
in nine pin. I also happen to be fond of octals:
6SN7
6SL7
Where to go with all this? Oi! I've got a 3/4 finished balanced tube phono stage, and a 9/10 finished balanced line stage. (Your choice, 6922, 6SN7, IRF9610, and...maybe...JFET). There are a zillion topologies you could use. Follow that with permutations based on tube type and you can devote your life to trying to get one preamp circuit done.
So many devices...so little time...

Grey
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Old 31st May 2002, 01:51 AM   #7
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Dice:

Motor over to Amsterdam some day if you want to hear a Jocko SS phono stage.

Jocko
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Old 31st May 2002, 11:36 AM   #8
dice45 is offline dice45  Germany
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Jocko,

yes, curious! Who is the guy? email me privately. Could be i drop by when I see Guido Tent on occasion.

methinks not that tube gear is inherently better than SS gear, for that i do not understand SS gear well enough. It just happens that the best gear i know is tube gear and that my simple, mechanically working mind roughly understands what happens in tube amps but does not so with SS amps.

An extrordinarily good phono preamp is running here in Munich at Hartmut's place (hifidaddy). He too is Munich Triode Mafia member although he has his center of special skills on SS design. He can tell which SS sound how in which configuration and why. Restricted to the devices he has experience with, of course.

His SS preamp is outperforming many tube preamps i know. What a pity tube geeks don't take his SS preamp serious. He had it with him at Aarhus Triode Audition Festival 2000 and noone paid attention, "SS gear, snort!" Never heard SS gear sounding more musical and smooth than at his place. I could happily live with the stuff he builds.
Just, wanna build my own and loose my last shirt on it, too
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