Electronic Design Mag discovers High End Audio!

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Maybe because they still driving them with 12AX7 .....:p

No. Because Gu-50 look like trash cans. And were unobtanium for manufacturers of mass production of guitar and hi-fi amps when everything, from crap to jewels, was made on tubes. LS-50 was designed and manufactured by Telefunken for military and government applications. Later after WW-II it was captured and redesigned for Soviet military applications, like aircraft transmitters. The tube requires more precision equipment to align grids, and uses more expensive materials, like nickel alloy for anodes. That's why after being red dissipating 100+W shortly it still works as if it never happened.
 
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And one more surprise: I've found that smoothness of transfer function means lower distortions than it's linearity. I.e. attempts to improve quality of an amp with smooth transfer function by decreasing of distortions applying feedback makes transfer function more linear but less smooth. It decreases THD, but increases audible distortions.
That is not always true and not a surprise, my N2 has low feedback and only 9 transistors including the power mosfet and its current source, it could operating also with 8transistors in total. There are no easy way to get stable high NFB that could reach 1ppm THD and less, with only 7 transistors driving mosfet output. Low distortion in solidstate isn't always high feedback but the output stages could be linearized with good design.

Why need 1ppm? because it need to work as linear current amplifier that has linear forward and reverse transfer. 1ppmTHD V-amp results in around 0.01%THD I-amp (depend on I sense resistor used). 0.01% THD is the margin that my ears start to hear differences for H3 and up, H2 is 0.02%.

In N2. It just have crossover distortion rises when operating in 10kHz and up with high current 2ohm load.
Attached shows 800mA biased N2, crossover at 10kHz is only in micro volts. I am choosing 200mA because that crossover distortion is already inaudible in around 100mA. Test is also easily do with biasing switch.

You know? This kind of buffer (I call it power gain in the past, but not a good name) has linear load transfer from output to input that makes it sounds like what is at the input.
 

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Marantz was pentodes? Dynaco? Fisher? Quad? Leak? Luxman? (just to name a few power amps he reviewed back in the day)

For preamps with which Holt was intimately familiar, I can't think of any that were pentodes.

wouldn't matter much what preamp you used if ur power amp 'spits' in the upper mids, lower highs?

...besides, when has anyone published a negative review in a mainstream hifi rag?

_-_-bear
 
Careful, SY, you are being inaccurate in your statement about triodes vs pentodes (or beam tetrodes). For example, Marantz COULD be connected to triode with a switch, but it was usually used in 'Ultralinear' which is equally triode and pentode.
In 1965, we used to modify Fisher 500C receivers to triode operation, from PENTODE operation. Dyna was Ultralinear, and could be beat sonically by either Radiocraftsman (triode) or Marantz 9 in triode mode. Even Ultralinear is not perfect, just a good compromise between power and performance.
 
Gordon Holt never published a negative review? Are you kidding?

Irrelevant anyway, here was a guy who INVENTED so-called subjective reviewing and had far more experience and knowledge than anyone else doing it, then or since. So how do you explain away the change in the perception of "tube sound?" Or was Holt effectively deaf?
 
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