@directdriver
from "The Classic Williamson 1993 Style" by Bill Kleronomos (Sound Practices #4)
"An unusual method of applying active screen voltages to the tubes is used. Instead of the usual dropping resistors, I used a set of 5 Watt Zener Diodes for special benefits : screen voltage is always held at or below manufacturer's recommended value regardless of screen current. Distortion products are materially lower because of the stiffer screen supply provided by Zener regulation - this is especially true for the EL-34 pentode with its wider ranging screen current than the usual beam power tubes. And less screen voltage requires less bias voltage and therefore less peak signal voltage from the driver at max. output. Bench tests with EL-34s and 6550s in the output sockets confirmed an approx. 20% reduction in THD when the original dropping resistors were replaced by Zeners."
from "The Classic Williamson 1993 Style" by Bill Kleronomos (Sound Practices #4)
"An unusual method of applying active screen voltages to the tubes is used. Instead of the usual dropping resistors, I used a set of 5 Watt Zener Diodes for special benefits : screen voltage is always held at or below manufacturer's recommended value regardless of screen current. Distortion products are materially lower because of the stiffer screen supply provided by Zener regulation - this is especially true for the EL-34 pentode with its wider ranging screen current than the usual beam power tubes. And less screen voltage requires less bias voltage and therefore less peak signal voltage from the driver at max. output. Bench tests with EL-34s and 6550s in the output sockets confirmed an approx. 20% reduction in THD when the original dropping resistors were replaced by Zeners."
I know, I have all three: el84, el84m and 6p14p-ev. The last two have also 14W of plate dissipation vs 12W of standard el84.
Right!
I sold hundreds fo EL84M Sovtek but it is necessary to specify that is not a nominal EL84
The EL84M is good tube, of course.
Are there real test lab on this or not?
I am searching dìsomething without success.
Walter
Difficult to ask him, unfortunately:
https://www.radioworld.com/news-and-business/service-sunday-for-bill-kleronomos
I’m not affected by the ruler syndrome (😉), so if the affermation is linked to someone reliable and is reasonable, I get it as beliavable, minus a safety factor (because often good results come in perfect conditions, and most speakers are far from it):
in this case I keep the screen resistors for safety, I set zeners to have screens voltage well above what 40%UL would give (not to affect too much maximum power), and will see how better the driver will work.
I don’t expect that much advantage at nominal listening levels, but sensitivity is improved and it will better manage high levels.
https://www.radioworld.com/news-and-business/service-sunday-for-bill-kleronomos
I’m not affected by the ruler syndrome (😉), so if the affermation is linked to someone reliable and is reasonable, I get it as beliavable, minus a safety factor (because often good results come in perfect conditions, and most speakers are far from it):
in this case I keep the screen resistors for safety, I set zeners to have screens voltage well above what 40%UL would give (not to affect too much maximum power), and will see how better the driver will work.
I don’t expect that much advantage at nominal listening levels, but sensitivity is improved and it will better manage high levels.