What tubes for 7K6PP X-former

soundbrigade · 9th January 2008, 06:06 PM

I have started a project that was planned to end up as a PP-amp with triodes 50CA10. Transformers (all), chassis and some components are in place. I also had 4 tubes - 50CA10 - but now only 2 are working and it appears to cost me an arm and a kidney to get new ones, so ....

... considering what I have:
OP-transformers CXPP25-MS-7.6K
Mains transformer HE NT-8466 ,
what other kind of tubes (preferable odd kind of) could replace my 50CA10?
I have a bunch of 6L6, that could work, as well as 807. As I have made holes in the chassi for the 50CA10 (octal fits perfectly) and for two noval I really want to stick to tubes that fit in here (as much as possible), which rules out odd stuff like 829.

Here's the box:

GordonW · 9th January 2008, 08:18 PM

I note that on the datasheet I found for the 6CA10 (same tube, just 6.3v heater), that the plate curves are listed as BOTH 6CA10 AND 6JE6.

This means, most likely, that you could put in 6JE6s or 6LQ6 (interchangeable with 6JE6) and not change the operating point of the circuit, except for heater voltage. Of course, you'd need to install Novar 9 pin sockets and plate caps...

Regards,
Gordon.

kevinkr · 9th January 2008, 09:12 PM

Other ones to look at are the 6CK4 and 6AH4 - these both work well with plate to plate loads in this range. They're inexpensive, quite linear and the amplifier I designed and built years ago using 6CK4 sounded pretty good. (The cross coupled differential driver circuit though was not the best choice for driving the significant miller capacitance of a power triode.)

Eli Duttman · 9th January 2008, 11:20 PM

Kevin,

A quick look at the 6CK4 data sheet indicates the "El Cheapo" splitter/driver lacks sufficient gain and that AB2 operation might be feasible.

A Mullard circuit using a 6AB4 voltage amplifier and an ECC99 LTP should provide plenty of voltage swing, while "laughing" at the Miller capacitance of the "finals". If AB2 is used, buffer the LTP with IRFBC20 MOSFETs DC coupled to the 6CK4 grids.

soundbrigade · 10th January 2008, 06:23 AM

I've seen 6CK4 on occassions but has never given that tube any deeper thoughts. Will look into that.
Thanks!

9th January 2008, 06:06 PM	#1
soundbrigade diyAudio Member Join Date: Feb 2006 Location: Vaenersborg, Sweden	What tubes for 7K6PP X-former I have started a project that was planned to end up as a PP-amp with triodes 50CA10. Transformers (all), chassis and some components are in place. I also had 4 tubes - 50CA10 - but now only 2 are working and it appears to cost me an arm and a kidney to get new ones, so .... ... considering what I have: OP-transformers CXPP25-MS-7.6K Mains transformer HE NT-8466 , what other kind of tubes (preferable odd kind of) could replace my 50CA10? I have a bunch of 6L6, that could work, as well as 807. As I have made holes in the chassi for the 50CA10 (octal fits perfectly) and for two noval I really want to stick to tubes that fit in here (as much as possible), which rules out odd stuff like 829. Here's the box: __________________ /Magnus

9th January 2008, 08:18 PM	#2
GordonW diyAudio Member Join Date: Mar 2005 Location: Marietta/Moultrie GA	I note that on the datasheet I found for the 6CA10 (same tube, just 6.3v heater), that the plate curves are listed as BOTH 6CA10 AND 6JE6. This means, most likely, that you could put in 6JE6s or 6LQ6 (interchangeable with 6JE6) and not change the operating point of the circuit, except for heater voltage. Of course, you'd need to install Novar 9 pin sockets and plate caps... Regards, Gordon. __________________ Speaker Design, Restoration and Repair- since 1985.

9th January 2008, 09:12 PM	#3
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	Other ones to look at are the 6CK4 and 6AH4 - these both work well with plate to plate loads in this range. They're inexpensive, quite linear and the amplifier I designed and built years ago using 6CK4 sounded pretty good. (The cross coupled differential driver circuit though was not the best choice for driving the significant miller capacitance of a power triode.) __________________ www.kta-hifi.net

9th January 2008, 11:20 PM	#4
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	Kevin, A quick look at the 6CK4 data sheet indicates the "El Cheapo" splitter/driver lacks sufficient gain and that AB2 operation might be feasible. A Mullard circuit using a 6AB4 voltage amplifier and an ECC99 LTP should provide plenty of voltage swing, while "laughing" at the Miller capacitance of the "finals". If AB2 is used, buffer the LTP with IRFBC20 MOSFETs DC coupled to the 6CK4 grids. __________________ Eli D.

10th January 2008, 06:23 AM	#5
soundbrigade diyAudio Member Join Date: Feb 2006 Location: Vaenersborg, Sweden	I've seen 6CK4 on occassions but has never given that tube any deeper thoughts. Will look into that. Thanks! __________________ /Magnus

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Tube Noob! need help with tubes lots of tubes	therapy_fan	Tubes / Valves	15	29th January 2009 09:01 PM
WTT: Various tubes for 6CA4/EZ81 rectifier tubes	GordonW	Swap Meet	4	27th August 2008 12:37 AM
CV428 tubes (Loktal 807) tubes FS	mobyd	Swap Meet	3	2nd January 2008 11:26 AM
tubes+i-pod	tomtt	Everything Else	0	16th February 2007 11:49 PM
many new tubes and tubes meter for sale	elviukai	Swap Meet	4	30th October 2003 09:22 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read