RE: Pre Amp Tube Matching Question

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In Reply to: Pre Amp Tube Matching Question posted by scriabin on April 14, 2014 at 07:18:22:

Your preamp uses two 6922 tubes, I see. If you're looking for sonic consistency and good (proper) operating, then you should look for tubes with all 4 criteria met. How they're wired into the circuit is important.

Is it like this? (One tube for each channel)
Chan R - Tube1-Triode1 - Tube1-Triode2
Chan L - Tube2-Triode1 - Tube2-Triode2

Or like this? (Triodes from both tubes are used for each channel)
Chan R - Tube1-Triode1 - Tube2-Triode1
Chan L - Tube1-Triode2 - Tube2-Triode2

If each channel shares a half of each tube, balanced sections and subsequently matched pairs would be pretty key and ideal. The high-gain selection may be important; below-standard gain can result in a funny-sounding amp. And fact is, most new-production tubes are not consistent whatsoever. Variation in transconductance and gain can leave you with a tube that sounds entirely different than it's spec-adhering cousin. For example, JJ 12AX7's have a reputation of being below-spec, to the point where it almost sounds like a 12AU7-AX7 mix-up tube has been placed in the slot.

And doing a little reading on the Audible Illusions L2, apparently some say the unit operates reliably ONLY with the Russian 6922's (apparently a question of plate voltage). Anything else burns up quickly, according to this review I found:

"[...] But the unit has one fatal flaw – a design flaw. While the Audible Illusions web site claims that 6922 and 6DJ8 specification tubes, other than the stock Sovtek tubes, can be used in this unit, fact is, they can’t. The unit was designed to operate at higher plate voltage attributes specific to the Sovtek tubes rather than then operating parameters of the specification. My particular unit has destroyed, in a couple of days, every NOS 6922 and 6DJ6 that I have tried other than the Sovtek tubes.

So if tube rolling is something you think you might want to experiment with, this is not the unit for you. If you stick with the stock Sovtek tubes – and they are quite nice sounding – the tubes will last about two years. I put a pair of Amperex Bugle Boy 6DJ8 in this unit and they completely changed the sound of the unit. It was breath taking, but alas the tubes were fried after two days."

Eeep
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May your tubes be lively, warm, and long-lasting. Holy be thy heater.
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Follow Ups Full Thread

Topic - Pre Amp Tube Matching Question - scriabin 07:18:22 04/14/14 (7)

RE: Pre Amp Tube Matching Question - TubeAcolyte 09:14:18 04/14/14 (1)

RE: Pre Amp Tube Matching Question - scriabin 20:14:57 04/14/14 (0)

You have it wrong.... - ABliss 07:56:09 04/14/14 (4)

RE: You have it wrong.... - Nunki 09:22:19 04/14/14 (3)

RE: You have it wrong.... - ABliss 10:22:49 04/14/14 (2)

When matching is important... - Lee of Omaha 11:45:29 04/14/14 (0)

I believe that Nunki was talking about the topology of the gain stages - FenderLover 11:32:47 04/14/14 (0)

Follow Ups

RE: Pre Amp Tube Matching Question - TubeAcolyte 09:14:18 04/14/14 (1)

RE: Pre Amp Tube Matching Question - scriabin 20:14:57 04/14/14 (0)

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