Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 11th January 2011, 05:39 PM   #1
diyAudio Member
 
Join Date: Dec 2010
Default GE Jan 6550a for SET amp?

Hi, a bit of a newbie question. I have a separo se88i (SET), amp that I have tweaked, new coupling/decoupling and power caps. I am currently using reissue GL KT88 valves. They have done about 1500 hours and I think they are getting a bit long in the tooth. The reason for thinking this is that the side getter flashing has shrunk by a quarter to one third of it's original diameter and also the side flashings have small grey speckles on them when viewed through a magnifying glass. I have been looking at getting some NOS KT88 but they are very expensive, indeed more than the cost of my amp in some cases. The GE Jan6550a seems to be a reasonably priced NOS valve from the mid 80's. So is the GE JAN6550a OK to use with my amp? Is there any danger of damaging my amp?
  Reply With Quote
Old 11th January 2011, 06:01 PM   #2
hooman is offline hooman  Iran
diyAudio Member
 
hooman's Avatar
 
Join Date: Nov 2008
Location: tehran
hi
ge 6550 better some kt 88 ...and you can use ge 6550 in your amp.6550 and KT88 are interchangeable .how abut nos Tungsol 6550 ?
  Reply With Quote
Old 11th January 2011, 06:12 PM   #3
diyAudio Member
 
Join Date: Dec 2010
I have had a look at the tungsol, but unused nos ones seem to be expensive. What do you recon to the tungsol for sound quality? Think the GE Jan tubes have a higher voltage rating as well.
  Reply With Quote
Old 11th January 2011, 07:00 PM   #4
diyAudio Member
 
richwalters's Avatar
 
Join Date: Sep 2003
Location: Alps:Tube amp designs over 150W, SMPS guru.
Quote:
Originally Posted by bottletop View Post
................. The reason for thinking this is that the side getter flashing has shrunk by a quarter to one third of it's original diameter and also the side flashings have small grey speckles on them when viewed through a magnifying glass. I have been looking at getting some NOS KT88 but they are very expensive, indeed more than the cost of my amp in some cases. The GE Jan6550a seems to be a reasonably priced NOS valve from the mid 80's. So is the GE JAN6550a OK to use with my amp? Is there any danger of damaging my amp?
Seems like the material annealing process (outgassing materials) not properly done, and shortened to save costs.....not the case with true NOS where material quality was better.
The GE 6550A is a gem tube...esp with green insignia..one pays dearly for this and the performance.

1500 hrs is short for a KT88....thrashed ?...I may be wildly optimistic but I would be looking at min 5000hrs je noch conditions.
My Kenrad 807's in a modified Linear guitar amp from the late 1960's have just clocked up 23,000hrs and still in excellent emission. The 5U4 is completely the opposite story !

richy
  Reply With Quote
Old 11th January 2011, 07:30 PM   #5
diyAudio Member
 
HollowState's Avatar
 
Join Date: Aug 2006
Location: Taxland, New Jersey
Quote:
Originally Posted by bottletop View Post
The GE Jan6550a seems to be a reasonably priced NOS valve from the mid 80's. So is the GE JAN6550a OK to use with my amp? Is there any danger of damaging my amp?
If you can find GE JAN 6550As at a price you consider reasonable, grab all you can afford. They are a fantastic tube and were built to take it. I have a good quantity for myself. I use them in a modified Acrosound UL-II that has 600 volts on the plates/screens. They've been in there for years with no problems at all. And a friend of mine in NY has them in a Citation II I sold him and loves them. And they will not hurt your amp. Usually it's the other way around.
Attached Images
File Type: jpg citation.jpg (115.5 KB, 87 views)
__________________
"It is hard to imagine a more stupid or more dangerous way of making decisions than by putting those decisions in the hands of people who pay no price for being wrong." ~Thomas Sowell
  Reply With Quote
Old 11th January 2011, 07:33 PM   #6
diyAudio Member
 
Join Date: Dec 2010
No the valves have not been thrashed. Indeed the amp has seldom been past half volume. I have just pushed the button on a pair of 1978 GE Jan6550a valves. Unused matched pair in original boxes. White label type with the brown bakelite base. Also got my eye on a matched pair of 1985 (black base), ones as well. Thought I'd get some tubes for a rainy day. I did not know that 5000 hours is what one can expect from a KT88. But 23,000 hours is serious! I was getting a bit concerned as my kt88's are glowing blue straight from the amp being switched on. They only use to start to glow blue after about half an hour or so. No violet colour though.
  Reply With Quote
Old 11th January 2011, 08:01 PM   #7
diyAudio Member
 
Join Date: Dec 2010
Thank you for the information Hollowstate. I have bought the 85 vintage matched pair as well. They are a touch over a matched pair of modern winged C tubes. I also have it in writing they are new in the boxes and unused. Nice! Makes sense I guess about the amp hurting the tubes and not the other way around. I must point out that I know very little regarding electronics. All the tweaking I have done to my amp has been due to researching and a mate in the states who has helped allot with electrolytic cap advice. I did have some silmic II fitted but they did not work well with mundorf SIO caps. My friend advised me to try Nichicon muse caps and wow, a totally different amp! Some tube rolling has also helped. RCA clear tops 12AU7a and a Tele smooth plate 12AX7 has helped the sound no end. I have some RCA clear top black plate 7025a as well and they sound good with the clear top grey plates as well. RCA did make some nice tubes imho.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
6550a question for engineer? KJ2005 Tubes / Valves 59 24th November 2009 03:33 PM
6550A HF Amp tc500 Tubes / Valves 12 15th October 2009 10:07 PM
GE JAN 6072A Valves (Tubes) mozfet Swap Meet 1 2nd August 2008 02:34 PM
Tubes: NOS Cetron JAN 6336B quad set wildmonkeysects Swap Meet 0 1st May 2008 02:52 AM
sylvania & GE tubes airframe Tubes / Valves 5 31st July 2006 10:31 PM


New To Site? Need Help?

All times are GMT. The time now is 10:19 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2