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In Reply to: 26 instead of 27 driver w/45 posted by audiobag on January 29, 2007 at 13:07:23:
I guess the only direct substitute for the 27 is the 56, and it is the only 'garbage' tube I ever encountered.I believe I would rate the following 45 amps the following way but all are excellent.
1) 6sn7/26/45 a clear winner.
2) 717a/45 excellent sounding with the pentode driver.
3) 6sn7/27/45 a really great amp until the 26 came along.
I believe the second and third position are correct but I never did a direct comparison. first place is sewed up.
Follow Ups:
Hmmmmm . . . each to his own, and I'm usually philosophically aligned with njjohn. But lest the 56 be damned by no praise, I certainly don't consider it junk. My Loesch Triple-2A3's were inputted and driven by 56's by design, and substituting 27's in either position virtually destroyed the PRAT and hallucinatory magic of which those amps were capable. In fact, in my zeal to find the "right" 27, I amassed a huge collection including mesh 227 and 327's, none of which were acceptable in that configuration. Damned if those tubes don't make great line stages though, particularly the meshies, which sound majestic by comparison to other 6SN7 precursors. But 56's junk? I think not. Not nearly.
> My Loesch Triple-2A3's were inputted and driven by 56's by design <I would love to be able to see a schematic and parts list for that amp. I would like to see what made this combo work.
Kurt, I never was provided, nor did I develop, a schematic of those amps. And I also recollect that John Wiesner, who built 'em, wasn't crazy about releasing his schematic. Top quality parts though: vintage Hammond iron, Black Gate WKZ's, Mills non-inductives, Electra-Print OPT's, Rel-Cap teflons, etc., immaculate workmanship. The amps had a stop-you-in-your-tracks tone and gut-wrenching immediacy. Listening to 'em, on a good night, was an event. Yes, they were, horror of horrors, paralleled 2A3's; but by some large margin, best amps I've ever owned.Regards,
I guess the only direct substitute for the 27 is the 56, and it is the only 'garbage' tube I ever encountered.>I have quite a few of these I haven't yet used for a project. I thought people spoke highly of them - don't they sound very similar to the 76? Why garbage?
The 56 is bright and brittle compared to the 27. If you need a bit more HF energy then maybe the 56 would sound better, but I have not found any real case where the 56 bettered the 27, except by having a little extra gain. I never heard the 76, and discounted its use after the 56/27 comparison I made. Maybe the 56 can overcome a really sluggish oil cap, but you're better off with a good cap and a 27.
Thanks for that - gives me an idea what to look forward to.
is there a public schematic for this amp?
Thanks in advance
I don't think there is. There are seperate schematics for the 6sn7, 26, and 45.The builder of the amps passed away and I believe he does have a schematic of the 26 amp but I have to wait some time before the family is ready to help out.
And I can recommend it with the vintage opts that he used because there is an interaction between the design and the opts. It may be as good with other opts but I can't vouch for it.
x
I guess i shouldn't have generalized so much about the 56. i believe I tried to substitute it in only one amp, and as described it has more gain than a 27 but it did not sound good. I think I had purchased a few of them on ebay, and I thought i wasted my money on this tube. But perhaps nothing can be discounted the way I did it.The opts are particular vintage Hammond opts. Some are in amps built be Webster and I think they are in what are called tone cabinets which are speaker cabinets (with an amplifier) which were built specifically for organ amps in the 1940's. I believe they were 2a3 amps. The other ones were bigger opts in larger chasses and I'm not sure what they were in. the latter were built in the 50's. I think the first one has 60 dc resistance, and the latter ones had 120 dc resistance. I think the latter ones may have been in 6v6 amps and maybe other kinds too. They were also organ related amps.
The opts are push-pull but they are used in single ended operation which was also done by Korneff with Sansui opts in his early amps.
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