What bias voltage (current)used at overture?
Did you use multimeter or oszilloskop? Thanks..
Multimeter measuring DC voltage.
set to a resolution of 2000.
For Overture and Melius,
Kondo state 0.5 mV to 0.55 mV.
But in reality I couldn't get those numbers.
I thought I had a faulty multimeter, so I tried with another and got the same numbers.
With the old tubes turning the potentiometer all the way down and almost all the way up (I was afraid to burn the tubes), I got 0.03 mV to 0.2 mV.
Tried some EL34 NOS I had... same thing.
I bought brand new Mullard EL34s (not NOS), and I got a minimum of 0.078 mV and a maximum of 0.2 mV.
So I couldn't rely on Kondo's procedure.
I would have to use my ears.
I noticed that adjusting 1 potentiometer affects all the other 3 in a way that it's lowering the voltage or increasing it.
For the last couple of weeks, I think I adjusted the bias about 4-5 times because something wasn't quite right with the SQ.
which can be so tedious as the overture has so many screws... and now I think I have become a master in it.
With the Kondo Overture, if you pin your ear to the woofers, you hear complete silence! with almost no hum, which is amazing for a tube amp!
So there were a couple of variables to get the best sound from the Overture:
- My ears.
- Leaving the amp powered on for more than 30 min (Kondo procedure state 15 min is enough).
- the slightest woofer hum in one of the speakers (there is always one that hums if the voltage is too low or too high).
- Tweaking the potentiometers for the most stable and exact voltage in all 4 tubes.
As I mentioned, tweaking 1 potentiometer affects all the others.
The best SQ with dead silent hum in both of the speakers, I got with 0.088 mV with the new Mullard EL34.
I can confidently testify that the overture now sounds the best it has ever been!!
and with new tubes, only one word come to mind, 'pristine' sound.