KT88 in JTM45

Don Borro · Post by **Don Borro** » Sat Apr 01, 2006 3:43 am

Is this possible without biassing ? Do you get bigger tone ?

BashCoder · Post by **BashCoder** » Sat Apr 01, 2006 8:11 am

The main thing about the KT88 is that a pair of them in push-pull can yield 100 watts of output power. But that's running them at 550V with a load of 4k ohms. The JTM45 would run them at 400V with a load of 8K ohms, which would yield less than 50W. So in that circuit the KT88 might work as a replacement. Maybe you'd want 1K on the screen grid resistors instead of 470. (Larry?)

Has anyone tried this?

BashCoder · Post by **BashCoder** » Sat Apr 01, 2006 8:12 am

Oh -- and you would have to rebias for sure.

fatihelloween · Post by **fatihelloween** » Fri May 18, 2012 5:34 am

I also want to try KT88 in my JTM45 if possible ?

Thanks,

robert · Post by **robert** » Sat May 19, 2012 11:45 am

Hi,

for a relatively "correct" KT88 (primary) impedance in a JTM45, you must change the (secondary) Speaker- load:

2 Ohm cabinet: connect to the 4 Ohm OT- tap
4 Ohm cabinet: connect to the 8 Ohm OT- tap
8 Ohm cabinet: connect to the 16 Ohm OT- tap

Regards

Robert

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KT88 in JTM45

KT88 in JTM45

Re: KT88 in JTM45

Re: KT88 in JTM45