Which KT-88 tube?

[FSHZ:42]

Originally Posted by fandersen

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!!!

[multi]

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

[FSHZ:42]

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!

[Jim McShane]

Originally Posted by FSHZ:42

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"?

[FSHZ:42]

Originally Posted by Jim McShane

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.

[AJT]

perhaps you mean mA?

or a 1ohm cathode resistor drops 60mV when a current of 60mA passes thru it....