GE Jan 6550a for SET amp?

[bottletop]

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?

[hooman]

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 ?

[bottletop]

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.

[richwalters]

Originally Posted by bottletop

................. 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

[HollowState]

Originally Posted by bottletop

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.

[bottletop]

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.

[bottletop]

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.