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Help needed choosing tubes for amp!

71.36.198.67
Posted on November 1, 2009 at 16:34:25
JSTRM
Dealer

Posts: 176
Location: Montana
Joined: March 7, 2003
 Hello everyone!
I need some advice. I’ve got a variety of different tubes that are used for audio amps and would like to build some kind of power amp. I've built some guitar amps with great success. Tubes are all NOS. Anybody have a schematic or idea on an amp using a combination of some the following tubes:
I’m looking for simplicity, SE or P-P.
801A/VT-62
RK-34/2C51 dual triode
6C4
6SL7
6SN7
7788
5932
I know this is a weird grouping, but I’ve been setting these aside for a few years in hope of building after retirement. That would be now.
Any ideas?
TIA!!!
V/r
CW
clumpster@earthlink.net
FYI RK34 () 2c51 RE: Help needed choosing tubes for amp!, posted on November 2, 2009 at 07:27:10
Happy Bapphy
Audiophile

Posts: 17
Location: Michigan
Joined: December 13, 2006
 I have some of these neat looking dual power triodes - the rk34's. Their alternate designation is 2c34, not 2c51 which is a signal triode pair.

RE: FYI RK34 () 2c51 RE: Help needed choosing tubes for amp!, posted on November 2, 2009 at 07:33:04
JSTRM
Dealer

Posts: 176
Location: Montana
Joined: March 7, 2003
 You are correct. I meant to change that after going into the cave to get the correct number off the boxes - forgot to retype it.
Thanks much for the correction.
Yes, the RK34 is very nice looking. I'd like to use it somehow.
V/r
jstrm

No more 6550s?, posted on November 2, 2009 at 01:10:41
Frihed89
Audiophile

Posts: 8445
Location: Copenhagen
Joined: March 21, 2005
 Or have you found a better one?
"What did the Romans ever do for us?"
RE: No more 6550s?, posted on November 2, 2009 at 06:30:56
JSTRM
Dealer

Posts: 176
Location: Montana
Joined: March 7, 2003
 M,
No, got plenty left. Just looking to do something simple but good.
V/r
C

It's worth it!, posted on November 2, 2009 at 10:30:27
Frihed89
Audiophile

Posts: 8445
Location: Copenhagen
Joined: March 21, 2005
 I on the other hand am looking for a relatively low power class A PP amp to play the 6550s I have.

Good luck with your project.
"What did the Romans ever do for us?"
Basic Question First - How many Watts you need? (nt), posted on November 1, 2009 at 18:23:20
danlaudionut
Audiophile

Posts: 3564
Location: Upstate NY
Joined: June 6, 2002
 DanL
RE: Basic Question First - How many Watts you need? (nt), posted on November 1, 2009 at 18:51:19
JSTRM
Dealer

Posts: 176
Location: Montana
Joined: March 7, 2003
 Hey Dan!
Well, not too much. I don't have fancy speakers or anything and I listen at moderate volume. As long as it's clean and detailed...that's about all I'm lookin at.
I don't plan on dumping a bunch of $ on this (already got some real good systems) project.
Thanks for your input.
jstrm

RE: Basic Question First - How many Watts you need? (nt), posted on November 1, 2009 at 19:58:57
danlaudionut
Audiophile

Posts: 3564
Location: Upstate NY
Joined: June 6, 2002
 jstrm

The 801As aren't the most linear DHTs
so I would recommend PP for ~7.5 watts.
A basic 6SN7 tube loaded directly coupled
to a 6SN7 Long Tail Phase Splitter then
cap coupled to a pair of 807As.
I would use an Edcor tranny for the
LTP and output coupling.

DanL
RE: Basic Question First - How many Watts you need? (nt), posted on November 1, 2009 at 19:31:16
Eli Duttman
Audiophile

Posts: 6157
Location: Plainsboro, NJ
Joined: March 31, 2000
 OK,

KISS it is. ;>) How about Class "AB1" in UL mode. Edcor's model CXPP50-MS-6.6K should do nicely in the Mullard circuit I previously suggested. The FET buffers are not needed for "AB1".

Eli D.
RE: Help needed choosing tubes for amp!, posted on November 1, 2009 at 18:21:12
Eli Duttman
Audiophile

Posts: 6157
Location: Plainsboro, NJ
Joined: March 31, 2000
 Sylvania's 5932 data sheet shows a setup for 47 W. in Class "AB2". That seem's promising. A Mullard circuit with a 12AT7 section voltage amplifier and a 6SN7 LTP will provide the requisite voltage swing.

A link for the data sheet follows immediately.
http://www.mif.pg.gda.pl/homepages/frank/sheets/137/5/5932.pdf

Class "AB2" operation requires high current driver circuitry that's DC coupled to the control grids. So, buffer the LTP with IRFBC20 MOSFETs, along the lines shown in MOSFET Follies.

Are you willing to pay for custom O/P "iron"? If yes, separate screen grid or cathode feed back tertiary winding construction, would substantially reduce the amount of GNFB needed to yield an adequate damping factor.

Eli D.
RE: Help needed choosing tubes for amp!, posted on November 1, 2009 at 17:42:29
danlaudionut
Audiophile

Posts: 3564
Location: Upstate NY
Joined: June 6, 2002
 You have some gems there.
5932 is a 6L6 - nice in triode.
Then the 6SL7 and 6SN7 of course.
The 6C4 would be a good preamp
or first stage integrated tube.
The 801A/VT-62 is good for 1.5-4W out.
How about a 6C4/5932/801A?
Interstage or cap coupled?
SE for 4W or PP for 8W?
Cheap or budget or all out?

DanL
RE: Help needed choosing tubes for amp!, posted on November 1, 2009 at 18:04:36
Eli Duttman
Audiophile

Posts: 6157
Location: Plainsboro, NJ
Joined: March 31, 2000
 I disagree about the 6C4. It contains the same triode as the 12AU7 twin. That triode has linearity problems, when used as a voltage amplifier. OTOH, it's OK as a cathode follower or as a "concertina" phase splitter.

Eli D.
RE: Help needed choosing tubes for amp!, posted on November 1, 2009 at 18:21:22
danlaudionut
Audiophile

Posts: 3564
Location: Upstate NY
Joined: June 6, 2002
 Eli

I drew some loadlines and you are right.
It is a 12AU7 in a single bottle.
Better off with the 6SN7 then.

DanL
Or a 6CG7/6FQ7................................... ~NT, posted on November 2, 2009 at 07:40:03
Cleantimestream
Audiophile

Posts: 1516
Location: Kentucky
Joined: June 30, 2005
 ~!
"The Sound of One Hand Clapping is Crashing by Design" HKM
RE: Or a 6CG7/6FQ7................................... ~NT, posted on November 2, 2009 at 07:44:08
danlaudionut
Audiophile

Posts: 3564
Location: Upstate NY
Joined: June 6, 2002
 Not one of the tubes listed on the original post.
Poster wants to make something from stock
that he has on hand.

DanL
RE: Or a 6CG7/6FQ7................................... ~NT, posted on November 2, 2009 at 08:31:08
Cleantimestream
Audiophile

Posts: 1516
Location: Kentucky
Joined: June 30, 2005
 Thank you Dan for pointing out {the obvious} to me...........time and again I will cheap chisel areas of my life ie {drive older cars}as to facilitate not cutting any corners for audio...........others have better balance than I.
"The Sound of One Hand Clapping is Crashing by Design" HKM
JAN-CHS 5932, posted on November 1, 2009 at 18:04:14
FenderLover
Audiophile

Posts: 3313
Joined: July 31, 2007
Contributor
  Since: May 17, 2009
 I put two brown base black-plate JAN-CHS into a Fender Pro amp awhile back. Bias and plate voltage in the range of a 6L6GA. Thing really gave the amp a much warmer, browner tone (than the stock 6L6GC). If I ran the 5932 around the stock 6L6GC settings, the amp distorted too early (in the volume range) and the tubes ran noticeably hot. Biased lower (more conservative idle dissipation), gave the amp almost a Deluxe or 6V6GT tone. With even more headroom. Very nice. FWIW.

Funky looking tubes. Kinda squat. The Sylvania had green lettering on the light brown base. Straight glass envelope.

RE: JAN-CHS 5932, posted on November 1, 2009 at 20:19:11
JSTRM
Dealer

Posts: 176
Location: Montana
Joined: March 7, 2003
 FL,
I figured they'd sound pretty nice when biased up right. I tried something similar a few months back, but the set-up was too high, so I didn't bother with it again. Personaly, I like the 6L6GB blackplates made by GE in late 50's/early 60's. They're great in tweed Fenders.
jstrm

RE: JAN-CHS 5932, posted on November 1, 2009 at 18:19:44
danlaudionut
Audiophile

Posts: 3564
Location: Upstate NY
Joined: June 6, 2002
 FL

Sounds like a better driver than output tube.
Good to know.

DanL

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