[Delta77]

I just installed some Sophia Electric KT88’s in my Decware (Zen Mystery Amp) and they want to bias much higher than the EL34’s I was using..
The KT88’s want bias around 70-80
The EL34’s biased around 20-30
Does this sound about right..??
Is there anything to worry about running around 80..??

[FullRangeMan]

If this amp are auto-bias as the other small ones its OK.
The owner manual say what?

OBS.: Looking the Decware site I see this amp not auto-bias, you will havr to read the manual or ask at the Decware Forum.

[Delta77]

I got it to bias around 66mA ,
Seems a little safer..
 I will keep an eye on the transformers temperature..

[Freo-1]

Yes, the KT-88 does bias higher than the EL-34.  I would tend to think that 70 ma or less for the KT-88 should be OK.

[FullRangeMan]

The inspire Fire Bottle bias at 23V 63mA for the KT88 to 11W.

[Francois G]

I just installed some Sophia Electric KT88’s in my Decware (Zen Mystery Amp) and they want to bias much higher than the EL34’s I was using.
Is there anything to worry about running around 80..??

As previously suggested, check the manual. 80ma per KT88 sounds high. Are you running now @around 60ma per tube? Any over-heating of the power or output transformers evident?

[Francois G]

I spent a few minute on the DECware website to see if I could get any helpful information.

This is what I found:
INPUT TUBE CHOICES: 6N23P, 6922, 6N1P, 6DJ8, 7DJ8
OUTPUT TUBE CHOICES: EL34, 6CA7, KT77, KT66, 7027, 5881, 6L6G
IDLE CURRENT: 40~60 MILS PER OUTPUT TUBE - ADJUSTABLE
HIGH B+ VOLTAGE: 410 VDC WITH LOAD

Notice that there is no mention of KT88 as output tube? Notice that the maximum allowable idle current is 60 ma per output tube. I believe these are set by the designer based on the power transformer used. Could be conservative, but since the amp is quite expensive, I would tend to stick to the “approved output tubes, and idle currents”.