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Hoffman Amps Forum image Author Topic: KT66 for EL34 in 5f6a?  (Read 2022 times)

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Offline Oddvar

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KT66 for EL34 in 5f6a?
« on: October 16, 2016, 06:34:15 am »
Hi.  Is it any way one can swap KT66 into an EL34 figured 5f6a amp?

Best.

Offline tubenit

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Re: KT66 for EL34 in 5f6a?
« Reply #1 on: October 16, 2016, 07:19:55 am »
IF your PT can handle the increased current draw on the 6.3V heater wiring and the increased draw on power tube current, then I think you could use KT66. 


I think (?) that there is  KT66 with less heater current draw but that it has a metal base that will not work with bear claws.



You may have to rebias or change the bias reisistor or pot values.


With respect, Tubenit

Offline Oddvar

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Re: KT66 for EL34 in 5f6a?
« Reply #2 on: October 16, 2016, 10:14:35 am »
The 6.3 v has 5 ampere?

Offline shooter

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Re: KT66 for EL34 in 5f6a?
« Reply #3 on: October 16, 2016, 11:15:01 am »
you're probably good on filaments, but like Tubnit said, you'll probably need to adjust bias, and possibly drive signal to the tube.  I played around on a SE amp and could swap in/out an 88, 34, or 6550 without tweaking until I settled on one, then I re-biased, but you have fixed bias, so that is more critical.
Went Class C for efficiency

Offline Oddvar

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Re: KT66 for EL34 in 5f6a?
« Reply #4 on: October 16, 2016, 01:21:10 pm »
I have installe biaspot, so that would be ok?

Offline shooter

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Re: KT66 for EL34 in 5f6a?
« Reply #5 on: October 16, 2016, 06:50:03 pm »
Quote
so that would be ok?
double check it's range before you plug in the new tubes. 
you have 1ohm bias R's installed?  makes it pretty easy to adjust bias, couple meters and you're there.
Went Class C for efficiency

 


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