on Thu May 14, 2009 9:50 pm
jrethorst
Thank you.
The Dynaco Tube Audio Forum » Basket » EL 34 v. KT 88 » New post
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on Thu May 14, 2009 11:22 am
GP49
Ohm's Law:
V = IR
Voltage at Biaset point = current multiplied by the cathode resistor value.
In a typical stock Mark III the cathode resistor is 11.2 ohms.
If you want 40mA of current in each tube, which others on this list have recommended for current production EL34, that makes a total of 80mA for two tubes.
So:
0.080 x 11.2 = 0.896 volts. Call it 0.9.
Substitute other values of desired idle current and cathode resistor if desired and/or needed. For reference: in the Mark II, Dynaco ran EL34s at 65mA but those were original Mullard tubes that were more rugged and long-lived than current Russian, Eastern Euro and Chinese EL34s. In the Mark III, Dynaco ran 6550s at 70mA.
on Thu May 14, 2009 4:52 am
jrethorst
How much is a little for the bias?
on Tue May 12, 2009 5:09 am
RockyAM
There are no wiring changes to run EL34's in a Mark III. Just plug them in. I would bias them down a little. Just understand that they probably won't last as long as KT88 or 6550 tubes in there.
Bob
on Mon May 11, 2009 11:45 pm
jrethorst
What wiring changes are there to run EL34's in a Mk3? In addition, are there other changes in addition to:
http://dynacotubeaudio.forumotion.com/basket-f2/run-your-dynaco-st-70-mark-ii-mark-iii-or-mark-iv-in-triode-mode-photo-t41.htm?highlight=mk3+triode
to run in triode mode?
Thank you.