I went ahead and tried the Buz900/905's. Now it works, no crossover distortion. No adjustments needed. I haven't had time to test the bias current but there is no apparent crossover distortion. The BUZ pair however doesn't have the input protection diodes like the 2SJ49 and 2SK134.
I'll just go on and build a dedicated BJT amp. I am not sure how the feedback circuit will work with the BJT instead of MOSFET.
BTW, this is not a hifi amp. Two of my bass amps make terrible treble. They are really only meant for bass guitar.
I'll just go on and build a dedicated BJT amp. I am not sure how the feedback circuit will work with the BJT instead of MOSFET.
BTW, this is not a hifi amp. Two of my bass amps make terrible treble. They are really only meant for bass guitar.
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I got to look closely today with a triangle wave , and no detectable crossover distortion. Doing great.
Previously, it had a strange sort of crossover in which the wave came up from negative, draws a short flat line on ground then jumps up vertically to +.3 volts, makes the upper sine half, dropped -.3v from ground, drew a short flat line, then jumped vertically to -.6v.
Looked to me what a vertical MOSFET with a lower than normal Vgth would do.
Previously, it had a strange sort of crossover in which the wave came up from negative, draws a short flat line on ground then jumps up vertically to +.3 volts, makes the upper sine half, dropped -.3v from ground, drew a short flat line, then jumped vertically to -.6v.
Looked to me what a vertical MOSFET with a lower than normal Vgth would do.
There were "Logic Level" vertical mosfets with Vth in the same range as laterals. Unfortunately the temperature coefficient was very high
I sort of like lateral mosfets, they save some work in the gain and feedback circuits. Voltage dependent circuits seem usually easy on the control circuitry. Current linearization isn't super difficult in BJT amps.
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