Re: Anyone try one of the new Marshall Origin 50 heads yet?
Awesome. It uses EL34s - are KT66s a suitable replacement?
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The 50 watt or the 20 watt Origin?
KT66 can be used in place of an existing EL34 as long they physically fit in the head shell, and in the case of fixed bias (the 50 watt Origin) if the bias pot has enough range to adjust the bias.
The EL34 already consumes slightly more heater current than KT66, and in most cases already uses a larger screen grid resistor than required by KT66.
With KT66 it doesn't matter if the tube socket has pins 8 and 1 externally jumpered or not. It usually must be with EL34.
With the 20 watt being cathode biased the bias is not something you need to worry about. Just plug em in and go.
The KT66 will not be quite as loud as EL34s
With both, bear trap style tube retainers usually don't work with KT66 because the bases are too big and often tapered. Some reissues use metal bases and that certainly won't work with bear traps. These are easily removed with a screw driver though. Additionally, most KT66s are just physically much taller and fatter than EL34s. The Chinesse KT66 is even taller than the Russian and JJ KT66 reissues.
