Biasing a Shiva

twangbanger

Member
Messages
1,492
Got a set of =C= EL34's for my Shiva and when I ordered them I told the Vendor that they were for a Shiva and he told me to get them w/ early breakup due to the high plate voltage.installing them I can't get the idle current up past 45ma w/ the bias trim pot.doesn't that seem to cold? Haven't checked for crossover dist yet.I'm using a weber bias right socket set up. Plan on calling Bogner but was interested in opinions from our tube amp guru's here.Thanks for any help.
 

frankencat

Guitarded
Silver Supporting Member
Messages
12,841
That does seem pretty hot for EL34's at 521VDC. I wouldn't go much past 35ma at that voltage. FWIW, I called Bogner once to ask them how they bias and they told me they use a scope and that I would not be able to bias it correctly without one. :rolleyes: The first Shiva I bought was biased way cold and even cranking the trimmer all the way down only got it into the low-adequate range for a pair of SED 6L6's.
 

Blue Strat

Member
Messages
30,067
34mA would be 70% which is too high.

Low 30s would be more like it. At 45mA you're almost at 100% plate dissipation which is a VERY bad idea.
 

twangbanger

Member
Messages
1,492
Thanks so much for the info,I should have done the math! Always pays to ask, Especially on this forum.
 




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