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Old 21st February 2012, 02:25 AM   #31
FSHZ:42 is offline FSHZ:42  United States
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Quote:
Originally Posted by fandersen View Post
There is no need to replace the 5751 tubes, unless you want to
I was told that the NOS GE 5751 were among the best sounding pre-amp tubes. I went to a site that has them, but they are on the high $$$ side.

I was also told that the Phillips JAN 5751 ECC's, which I am presently using, are at the bottom of the pole.

I am not sure what to believe! Maybe someone here can give me their inputs!

Thanks!!!
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Old 3rd March 2012, 07:43 AM   #32
multi is offline multi  Australia
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I don't think you need to run KT88's at more than 50 ma per tube.
90 ma would burn them out fast. GEC with the original KT88's, recommended that anything above 35 mills was plenty.
Phil
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Old 6th March 2012, 02:37 AM   #33
FSHZ:42 is offline FSHZ:42  United States
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Hello Multi,

I was referring to the voltage not amperage. The GL Genalex KT88's are run on my amps at around 90mV. I run my SED Winged "C" tubes at around 62.5mV. I have not had any problems, except for the GL tubes on one amp reading out of the specific range tolerances.

It has been known that the GL tubes have had these issues in the past.

Thanks for your reply!
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Old 6th March 2012, 10:10 PM   #34
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Quote:
Originally Posted by FSHZ:42 View Post
Hello Multi,

I was referring to the voltage not amperage. The GL Genalex KT88's are run on my amps at around 90mV. I run my SED Winged "C" tubes at around 62.5mV. I have not had any problems, except for the GL tubes on one amp reading out of the specific range tolerances.

It has been known that the GL tubes have had these issues in the past.

Thanks for your reply!
What do you mean by "specific range tolerances"?
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Old 7th March 2012, 12:34 AM   #35
FSHZ:42 is offline FSHZ:42  United States
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Quote:
Originally Posted by Jim McShane View Post
What do you mean by "specific range tolerances"?
I try to keep the voltages going into the output tubes at around a 2% tolerance. This means that if you are running a certain power tube at say 60mV (manufacturer specs recommendation @ 60mV), the 2% tolerance would be +/- 1.2mV.

This is what I meant by the "specific range of tolerances"

I left the "of" out.
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Old 7th March 2012, 03:39 AM   #36
AJT is offline AJT  Philippines
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perhaps you mean mA?

or a 1ohm cathode resistor drops 60mV when a current of 60mA passes thru it....
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Old Yesterday, 07:51 PM   #37
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any input on a good cheap kt-88,looking for a back up quad. just in case.
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Old Today, 12:11 AM   #38
multi is offline multi  Australia
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After many years of using Tungsol reissue KT88’s a friend purchased a large quantity of Psvane KT88’s. He runs an active system with 10 mono block amps then his troubles started the Psvanes took out all his amps. One or more tubes would blow the 10 Ohm cathode resistors, the G2 resistors when triode connected. Luckily he had bought the Psvanes from a USA distributer and they took the lot back. He has gone back to Tungsol and no problems for over one year much cheaper; I think the Psvanes cost $A100 each the tungsols in bulk less than $27.00 each. The amps run at 400-450 volts, 50 Ma.
The Psvanes came in fancy boxes: JUNK
Phil
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