Vintage Modern bias question

[kev67]

First time I’ve had a VM 2266c.
The tubes are ready for a change and have not experienced the kt66’s before.
I’ve seen that I can install 6l6’s?
If that’s true is it a straight plug in and bias or would I have to do anything else?
Any thoughts about having 6L6’s over the kt66?

Cheers in advance

 

[Jon Snell]

The KT66 is a power beam tetrode (hence the T in the name), the 6L6 is a Beam Pentode (hence the L in the name). (It's an American thing; some dissagree, some agree).
Their performance is very similar and although the bias point is slightly different, (adjusting the bias voltage is needed) they sound slightly different (the KT66 can deliver a lot more power) but some like the Pentode and others like the Tetrode knee point.
They are otherwise interchangeable, although the KT66 draws 1.3A heater current, the 6L6 900mA.
If you like the Pentode sound and all pins are wired on the sockets, why not try a set of EL34s if the bias will adjust accordingly.

 

[Spanngitter]

If you like the Pentode sound and all pins are wired on the sockets, why not try a set of EL34s if the bias will adjust accordingly.

It would require to bridge Pin 1 and 8 to make EL34 work properly in a VM.
They will work (if the Bias Range is sufficient), but in Tetrode Mode, not in Pentode Mode and the OT primary Impedance is also suboptimal...

 

[kev67]

Ah thank you guys kt66 it is then