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Old 25th October 2011, 01:19 AM   #11
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Originally Posted by fdegrove View Post
From experience I can tell you that matching anything like a 6080 and up in power is going to take more than just a few dozen of those bottles...
You're quite right about finding tubes with matched or close sections. Back in the eighties, when I was actively dealing in vacuume tubes for gain, a fellow dealer had a large collection of 6394A's in his inventory. Since we were friends, he allowed me to sort through all that he had of this number. I tested all of them at JFF Research in Nutley New Jersey. This was a testing operation that served all the surplus dealers nation wide. John was an engineer and an ex-employee of ITT also in Nutley. (still is) From these I was able to gather several dozen that were pretty close section to section. Not perfect, but above average in match. I've been saving them for a big OTL someday. With a 1 amp filament, paralleling them is easier. They're the same wattage as 6336A's, but the lower amperage makes things easier.
Eye candy below. Tubes on the ends have dust on the tops, not bad getters.
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File Type: jpg 6394+.JPG (126.9 KB, 212 views)
File Type: jpg 6394.JPG (133.4 KB, 204 views)
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Last edited by HollowState; 25th October 2011 at 01:21 AM.
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Old 25th October 2011, 10:29 PM   #12
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Hi,

Madre madonna...WOW. Nice stash you have there.

Have you any idea what type of OTL circuit those babes are going to go in?

Driver circuit?

Cheers,
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Old 26th October 2011, 12:51 AM   #13
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Hi,
Have you any idea what type of OTL circuit those babes are going to go in?
If and when I do get enough time and physic gasoline, it will surely be a Circlotron style like the Atmasphere. That's the one that makes the most sense to me, and the easiest to implement. Pretty basic circuit of long tailed phase inverter>diff amp>diff cathode follower to grids with fixed bias.
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Old 26th October 2011, 02:32 AM   #14
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I have heard excellent amplifiers with this kind of tubes (6AS7, 6336, 6C33C) especially when used cathode output.
I made an SE amp using 6336A's or any of the tubes with the same pinout and it sounded great. It was a cathode follower design using the "Augmented Cathode Follower" design as outlined in Ross MacDonalds 1957 patent. It made over 10 WPC limited by the OPT's and the power supply.

I now have a power supply capable of exceeding the needs for this amp, so I'll have to hook it back up some day.
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File Type: jpg FirstSmoke.jpg (292.9 KB, 178 views)
File Type: jpg RollingAlong_b.jpg (236.1 KB, 172 views)
File Type: jpg augmented_cf_sch_reduced_b-3.jpg (97.6 KB, 171 views)
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Old 26th October 2011, 04:15 AM   #15
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Originally Posted by pieter t View Post
This might be a great build:

Un ampli chargecathodique de 30 W (G.Marec)

30 watts cathode output ...
This is an interesting schematic but I found out the 6336A on eBay are very expensive compare to the 6080/6AS7 or the much more linear russian 6S19P ... But is maximum 30W plate dissipation is a great avantage to get more output power than with average power triodes.

Alain.
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Old 26th October 2011, 09:15 PM   #16
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Hi,

Being familiar with Marec's circuit I'm a little less enthousiastic.

This is one of he OTL schemes that appeared in L'Audiophile back in the seventies, right?. Hhmm, none of those were all that great.
Later on Buce Rozenblitt offered a design based around the less powerful 6AS7G which is a stable design close to what I drew up before he did.

That worked well with both 6AS7G and 6336As up to driving a sixpack of them.

In the end I still abandoned it as the 6336A's were not as stable as the 6080 (I much prefer those over the 6AS7G)

You know, tube like those aren't designed for this kind of use so you need to be aware of all the caveats....

IOW, currents drifting all over the place is what you may well get.... Grids being popped due to sudden current draw etc.

Ciao,
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Last edited by fdegrove; 26th October 2011 at 09:28 PM. Reason: Spelling
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Old 26th October 2011, 09:26 PM   #17
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Originally Posted by fdegrove View Post

Being familiar with Marec's circuit I'm a little less enthousiastic.

This is one of he OTL schemes that appeared in L'Audiophile back in the seventies, right?
No Frank, you are wrong.
Maybe you could click the article and see that this amplifier sports an excellent quality c-core transformer....
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Old 26th October 2011, 09:52 PM   #18
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Hi,

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Originally Posted by pieter t View Post
No Frank, you are wrong.
Maybe you could click the article and see that this amplifier sports an excellent quality c-core transformer....
Yeah, you're correct. So I scrap the OTL part, mentally.

Damm, I should kow better. Thanks for correcting me. Maybe these bottles are better suited for x-former use after all?

Think about that,
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Old 26th October 2011, 10:01 PM   #19
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Maybe these bottles are better suited for x-former use after all?
Especially with cathode output / output transformer coupling IMO very good amplifiers can be built using these class of tubes.
Checking the curves of the 6336A in the article, these look not bad at all, and using them as cathode followers will enhance linearity.
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Old 26th October 2011, 10:14 PM   #20
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Hi,

One of my "brighter" ideas was to x-former couple those low Z power bottles to the likes of Magnepan or Apogee type of speakers...

We keep on dreaming...

Cheers,
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