Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on August 16, 2014, 09:18:49 am

Title: KT77 max G2 voltage ? (tetrode connection)
Post by: kagliostro on August 16, 2014, 09:18:49 am

Reading on Genalex datasheet seems that KT77 used as tetrode must don't exceed 300v at G2

see page 3 on this datasheet

http://www.mif.pg.gda.pl/homepages/frank/sheets/086/k/KT77.pdf (http://www.mif.pg.gda.pl/homepages/frank/sheets/086/k/KT77.pdf)

is this correct or I've misunderstand and the 300v limit on G2 is as to have (with tetrode connection) performance similar to the UL connection ?

Thanks

K

Title: Re: KT77 max G2 voltage ? (tetrode connection)
Post by: shooter on August 16, 2014, 11:03:25 am

The 2nd line, absolute screen volts, shows 650v, absolute power, 6W.  Most everyone here seems to agree the old data sheets don't correlate well with the modern tube versions.  I've done a couple builds with KT88's and try and keep B+ in the 400-450 range, G2 around 300-350.  I typically start cathode current around 80-110mA, sometimes pushing it to 90 to 95% max I for SE builds and slightly less for AB builds.