EL34,KT66,6L6GC,KT77:who works better with high impedance OT load in SE Triode Mode?

[ygg-it]

Hello I need to know who has the highest impedance OT load requirement in SE Triode and linear mode.

I think 6L6CG>KT66>EL34 but I don't know where KT77 is positioned.

I have an impedance mismatch and I need a tube with the highest impedance load requirement.

Thanks

 

[JonSnell Electronic]

6L6 is 6.6k watch tghe screen grid voltage! An 807 is similar to 6L6 but can handle a much higher anode voltage due to the top cap.
KT66 is essentialy a 6L6 with a larger cathode and is a Beam Tetrode. There is no information on loading available as they have been obsolete for many years.
EL34 is happy down to 2k load at 250v HT.
A KT77 is happy with an HT up to 650v and a load of 6k.
All data is available on line. See http://www.drtube.com/datasheets/kt77-mov1977.pdf

 

[Tom Bavis]

Triodes aren't picky about load impedance - the "optimum" is a compromise between power and distortion. Go higher in impedance and you'll get less power and less distortion. For any given power supply and load, it's likely that the EL34/KT77 can swing more voltage, thus deliver more power. Though the higher the load, the less difference there will be between the tubes you listed. (BTW - modern KT66s may be relabeled 6L6GCs - check the heater current).

And output tubes AREN'T matched in impedance to the transformer. For Triodes, distortion will be very high if transformer impedance is same as plate resistance. Should be several times the plate resistance. For pentodes, there is an optimum load impedance giving the most power and lowest distortion, but it has nothing to do with plate resistance.

 

[azazello]

To chose load I multiply Ra to 3 for triodes or to 5 for penthodes.