6550 tubes

gianis · 11th November 2005, 04:15 PM

I found from military stock 20 [and maybe more ] 6550 Tung sol USA NOS in original JAN boxes. I want to build something powerfull with these tubes.. Any idea ? schematics? Thanks...

Eli Duttman · 11th November 2005, 04:55 PM

Drool!! Those are some NICE beam tetrodes and they are VALUBLE.

Somthing powerful, you say. Is 55 WPC or thereabouts powerful enough? A single PP pair in each channel will do that for you. You'll have to go PPP to get more power.

Selling some of the stock to raise cash that would go towards "iron" is an option open to you. You definitely want to use high quality O/P trafos.

If you can get O/P trafos of sufficient quality (not at all easy), "cloning" the H/K Citation 2 is something to consider. FWIW, I own a Cit. 2 and it's EXCELLENT.

SY · 11th November 2005, 04:57 PM

These are terrific tubes, easily the best 6550s ever made. In pentode mode with a 2000-2500 ohm plate to plate load, you can get 100 watts out of a single pair.

cogsncogs · 12th November 2005, 08:02 AM

@ gianis

Send me about 10 of them and I'll send you all the schematics you can handle, hehe!

Push-Pull pentode or Ultra-Linear with a nice driver stage and a brute power supply would be the way to go. Search the forum for 6550 and Push Pull, and see what you'll find! I'll search my computer and brain and post a few for you if someone doesn't beat me to it. Will this be for Hi-Fi audio or say a guitar amp?

Good luck!
Wayne

cogsncogs · 12th November 2005, 08:10 AM

@ gianis

Scroll down and look at this thread:
KT88 push pull

A KT88 is similar to a 6550. You may get some ideas from that thread.

Cheers
Wayne

gianis · 13th November 2005, 08:23 PM

Thanks for the responses..i`l try to do something maybe in triode mode.

shermanr · 7th March 2006, 02:05 PM

Did you ever build your 6550 amp?

I have one you may want to build based on the Triode Electronics MK3 PC board.

Attached find a photo of the front panel of one Monoblock.

richwalters · 7th March 2006, 07:05 PM

Quote:

Originally posted by SY
you can get 100 watts out of a single pair.

Follow schematics suitable for KT88 and one can't go wrong. In fact I regulary swap both tubes so long bias range can accomodate. If you really have the original A version 6550 then 100W per pair is pushing their lives. It would be a pity to slam a near-collectors item.
Watchout screen grid ratings in UL mode......my spec for 6550A g2 shows max 470V and with so many clones about I don't push g2 above 400V in UL.
To be honest, I've got a set of JAn 6550A (green logo) and I get more out of these than MO KT88's.
Parallel pairs in triode mode would sound very nice to my ears and the low Z is attractive. Lower B+ means longer life.

A drawback.... my 6550 spec shows a low grid leak resistance (max 50K) in fixed bias. This places the onus on a low distortion slam driver stage to provide the required swing.

richj

7n7is · 9th March 2006, 11:43 AM

I keep seeing references to this article on the internet:
Herbert I. Keroes, "Adapting the 'Ultra-Linear' Williamson to 6550 Operation," Radio & TV News, November 1955, pp.52-54, cont. p.136.
Does anyone here have a copy?
There's another article in Radio & TV News, November 1955, I think it starts at page 60, about a 6550 amplifier.

http://www.google.com/search?hl=en&l...55&btnG=Search

7n7is · 10th March 2006, 05:28 PM

I've got both articles in case anyone is interested.

11th November 2005, 04:15 PM	#1
gianis diyAudio Member Join Date: Jan 2004 Location: athens	6550 tubes I found from military stock 20 [and maybe more ] 6550 Tung sol USA NOS in original JAN boxes. I want to build something powerfull with these tubes.. Any idea ? schematics? Thanks...

11th November 2005, 04:55 PM	#2
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	Drool!! Those are some NICE beam tetrodes and they are VALUBLE. Somthing powerful, you say. Is 55 WPC or thereabouts powerful enough? A single PP pair in each channel will do that for you. You'll have to go PPP to get more power. Selling some of the stock to raise cash that would go towards "iron" is an option open to you. You definitely want to use high quality O/P trafos. If you can get O/P trafos of sufficient quality (not at all easy), "cloning" the H/K Citation 2 is something to consider. FWIW, I own a Cit. 2 and it's EXCELLENT. __________________ Eli D.

11th November 2005, 04:57 PM	#3
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	These are terrific tubes, easily the best 6550s ever made. In pentode mode with a 2000-2500 ohm plate to plate load, you can get 100 watts out of a single pair. __________________ If there's a sucker born every minute, where do the rest of them come from?

12th November 2005, 08:02 AM	#4
cogsncogs diyAudio Member Join Date: Jul 2003 Location: Wayne, West Virginia	Some guys have all the luck! @ gianis Send me about 10 of them and I'll send you all the schematics you can handle, hehe! Push-Pull pentode or Ultra-Linear with a nice driver stage and a brute power supply would be the way to go. Search the forum for 6550 and Push Pull, and see what you'll find! I'll search my computer and brain and post a few for you if someone doesn't beat me to it. Will this be for Hi-Fi audio or say a guitar amp? Good luck! Wayne

13th November 2005, 08:23 PM	#6
gianis diyAudio Member Join Date: Jan 2004 Location: athens	6550 Thanks for the responses..i`l try to do something maybe in triode mode.


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12th November 2005, 08:10 AM	#5
cogsncogs diyAudio Member Join Date: Jul 2003 Location: Wayne, West Virginia	@ gianis Scroll down and look at this thread: KT88 push pull A KT88 is similar to a 6550. You may get some ideas from that thread. Cheers Wayne

7th March 2006, 02:05 PM	#7
shermanr diyAudio Member Join Date: Dec 2004 Location: PR	Did you ever build your 6550 amp? I have one you may want to build based on the Triode Electronics MK3 PC board. Attached find a photo of the front panel of one Monoblock. __________________ Rich

9th March 2006, 11:43 AM	#9
7n7is diyAudio Member Join Date: Mar 2006 Location: VA	I keep seeing references to this article on the internet: Herbert I. Keroes, "Adapting the 'Ultra-Linear' Williamson to 6550 Operation," Radio & TV News, November 1955, pp.52-54, cont. p.136. Does anyone here have a copy? There's another article in Radio & TV News, November 1955, I think it starts at page 60, about a 6550 amplifier. http://www.google.com/search?hl=en&l...55&btnG=Search

10th March 2006, 05:28 PM	#10
7n7is diyAudio Member Join Date: Mar 2006 Location: VA	I've got both articles in case anyone is interested.

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