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In Reply to: RE: Physical Difference between EL34 & KT77 posted by -S- on November 12, 2009 at 02:37:21
Doesn't "KT" = kinkless tetrode? At least the KT-66 and KT-88 were originally advertised as having minimal "kink" in the sine wave curve between the transition of the positive and negative portions of the signal generated sine wave. Does the KT-77 have the same technology? Minimizing the "kink" during transition?Thanks!
Edits: 11/12/09Follow Ups:
"KInkless" refers not to a sine wave but to the actual plotted anode/grid curves of the tube under measurement.
A triode is linear, but tetrodes had a "kink" in the curve, which can be found in the radiotron Designer's Handbook.
The pentode was designed to eliminate this kink and patented, to avoid paying licensing fees, US companies developed the beam tetrode that effectly had the same "kinkless" curves.
Regards, Allen
These are the curves for a "kinkless" tetrode - a beam tube.
If it didn't have the beam plates, the curves would have a kink, a big ripple, just after the point where they start to flatten out, somewhere around the vertical "100V" line..
This makes the tube rather non linear through a mjor part of it's anode current swing, and hence unsuitable for good audio.
Regards, Allen
hey-Hey!!!,
And in this case there is a small kink in the curves. IME, the KT tubes just have a much smaller kink than beam-free tetrode designs do.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
...on the -30 volt line.
A pure tetrode would have bigger such kinks on most if not all of the lines.
Regards, Allen
Below is an example of the kinks one finds in the curves of a real tetrode. After looking at these curves, the significance of the designation "kinkless tetrode" becomes apparent. Some believe the KT series of beam tetrodes are more kink free than say a typical 6L6. Obviously, that's not the comparison the mfgrs where thinking of when they devised the term.
mt
The KT-77 should be a beam tube. They're built like the attached photo.
The EL34 should be a "true" pentode. It shouldn't have beam forming plates. Instead, there is a third grid winding (suppressor grid) in it's place. The screen grid and possibly the suppressor may or may not be aligned with the control grid. In the beam tube, the screen grid must be correctly aligned with the control grid, or the whole deal is off.
Do they have a different characteristic sound? You bet!
Did you scan that great pix our of the RCA Tube Manual, or is it available on line somewhere?
Regards, Allen
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