Whats a good Bias for KT88's in 20th Shiva?

[Adambomb]

Just checking to see what all you 20tg Shiva guys have your bias set in a 20tg KT88 Shiva after amp warmed up? Thanks

 

[Adambomb]

Bogners closed till Monday and I have show tonight. If anyone can tell me the bias of their KT88 20th Shiva after amp hot please let me know. Just want a normal bias range. I'm guessing 35-45ms but not sure.

 

[Adambomb]

Does ANYONE have any idea of the bias of a KT88 20th Shiva? Bogner IMHO always gives a cold bias suggestion. Anyone? Just a bias number...

 

[Rdodson]

They do recommend a cold bias because it drifts up pretty good if you run the resonance and master up. I can't remember the exact #, but KT88s are much more forgiving of a cold bias that EL34s.

 

[Adambomb]

Thanks for your input. I got them KT88's bias's around 38ma and sound great once amp is good and warmed up.

 

[Rdodson]

I converted one of my 20ths to EL34 and it was way less versatile - unless you were cranked the tubes were sterile and not coming out of crossover. It sounded "good" but not harmonically "GREAT!"

 

[Adambomb]

I converted one of my 20ths to EL34 and it was way less versatile - unless you were cranked the tubes were sterile and not coming out of crossover. It sounded "good" but not harmonically "GREAT!"

Yes these are some of the exact reasons I switched back to KT88's. But I've still yet to get anyone who can tell me what they set their KT88 bias.

I have mine set at around 37-40ma now and it sound great. Was just wondering if this was a safe bias range. And I set the bias after the amp is real hot like Bogner suggests since the bias drift.

UPDATE: Bogner said to bias KT88's around 35ma and EL34's around 29ma with the 20th Shiva.

 

[mesabog]

my 20th from the factory is biased at idle 28ma..when amp is played at gig levels it goes up to 48/54 maybe thats why they want it cold at idle.

 

[Adambomb]

my 20th from the factory is biased at idle 28ma..when amp is played at gig levels it goes up to 48/54 maybe thats why they want it cold at idle.

28ma for KT88's or EL34's? Thats more like an EL34 bias. Bogner STRONGLY suggests that the amp be VERY hot when checking idle bias. Like played for 30 mins loud hot... then check it. Oh yea, they bump up to to the 50's-60ma when really cranked. Thats why you can't just use regular EL34's "if" thats what you have. Any KT88 will work though. I've actually went back to EL34's, turns out I have 4 worn out SED EL34's and then put the KT88's back in and the tone came back, but then I found a couple more old SED's and put them in and the tone was even better and more old school rock, and less modern glassy sounding than the KT88's.

But either way, either tube, the 20th Shiva still will always be a legendary amp. I have mine w/EL34's bias'd at 30ma and it's perfect for me.

 

[mesabog]

mine has kt88's i checked it hot because i thought that was very low for kt88 tubes. i thought it was weird to be that low but im gonna leave it like the factory said