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Old 06-14-2018, 01:35 PM
Simonatsea Simonatsea is offline
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Join Date: Mar 2014
Location: Victoria, BC
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This just in from Dennis, apparently he is watching us.... LOL

Dennis wrote:
I firmly believe that the option of triode/pentode or triode/ul switching option is market driven. When one truly looks at the huge disparity in plate resistance of a vacuum tube in the pentode, beam power and tetrode configuration vs triode it is amazing. A simple example is the 6L6. The plate resistance in the pentode mode is on the order of 35,000 ohms. The same mighty 6L6 wired in the triode mode the plate resistance is on the order of 1700 ohms. The difference is night and day. The plate resistance of the tube will determine the proper primary impedance and ratios of the output transformer in the tube amplifier. An example of the 6L6 wired pentode would operate properly with a primary impedance of 7000 ohms. Take the same 6L6 wired triode the impedance is now on the order of 4500 ohms. I prefer to use a 4300 ohm primary for the basic beam powered tubes wired as triodes. The ultimate sound quality of a high performance vacuum tube amplifier is so dependent on the proper impedance and ratios of primary to secondary windings of the output transformer.

Anyway … I could go on and on . but simply stated … the differences are much too great in the sonic results of a compromised, market driven triode/pentode/ul switch. Give me some time and I could really let you know what I think of the ultra-linear (ul) mode of degenerative negative feedback!!!!!!!!
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