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Old 16th January 2012, 02:31 PM   #171
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Default prior art

Sorry, but prior art fig. 1 does NOT lead to AB2. Fig.1 is a dead end.
AB2 was derived from AB1.

Cheers,
E.
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Old 16th January 2012, 02:52 PM   #172
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I am using different ways with my XM, it has floating supplies for its non switching mechanism, and direct driving from inputs, the result is just faster, no more.
I see no differences within kendall's and nakayama's type.
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Old 16th January 2012, 03:03 PM   #173
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>I see no differences within kendall's and nakayama's type.
I don't see it either. See also: New Linear Audio publication!
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Old 15th February 2012, 12:20 AM   #174
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May be this one is better than old version of non feedback pioneer's, 0.1V drop voltage for normally 1V drop without it, no feedback (input compared FB).

Found it at AR D400 and may be soulution I don't really know for this. I search for any patents and negative.
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Old 15th February 2012, 09:47 AM   #175
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If I understand correctly, the six transistors at the left side provide error cancellation (to a certain extent). However, this part of the circuit is output voltage controlled whereas the actual needed amount of error cancellation depends on the output current. So this compensation scheme works only as intended with a fixed resistive load.
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Old 15th February 2012, 01:58 PM   #176
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While I obsessed upon Schottky diodes being the only devices to switch off,
there are stability advantages to letting the common mode feedback devices
turn off. Its a real pain to compensate two loops that interact nonlinearly,
even at 90deg.

I think Edmond's way (and Elvee's cirlophone way) are better ideas, even
if transistors in the common mode loop are regularly turning off. Its not in
the differential loop where you would hear it. The mixing of compensations
is far less messy when you allow for the shutoff.

Last edited by kenpeter; 15th February 2012 at 02:00 PM.
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Old 16th February 2012, 06:33 AM   #177
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It is load dependent, but it smoothen crossover distortion to a level that could be reduced with negative feedback that normally has slow response. Also its load dependent is not harmful, may be with mosfet like in AR D400, or more diode arrangement, it has better smoothening result. Soulution 710 gets very low THD <10ppm without NFB, don't really know what they mean with without feedback.
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Old 16th February 2012, 02:03 PM   #178
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The failing of that one is the same as every ordinary AB emitter follower.
Nonlinear common mode feedback is shaped by output devices that are
not at constant temperature. Sims may not reveal the obvious here.
Even you compensate some desired non-linearity beforehand, those
hot output devices (and also load impedance) are not to be trusted.

Common mode negative feedback (aka quadrature feedback in other
threads). Even ordinary AB amps with a sliding bias of fixed voltage
already have this. Its actually a concept we are already familiar with.
Something sets output quiescent current, emitters and resistors, else
it runs away! But the braindead way this is usually handled is neither
temperature independant, nor produces the desired non-switching.

All the good circuits use supplemental devices of oversized thermal mass
and low dissipation to monitor the true currents, and make well informed
decisions about how to shape bias for ideal current non-linearity. Hopefully
to make gentle non-switched crossings with any load. Output devices that
do hot work are not permitted to participate in decisions about current.

Last edited by kenpeter; 16th February 2012 at 02:18 PM.
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Old 16th February 2012, 07:54 PM   #179
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>Output devices that do hot work are not permitted to participate in decisions about current.

Well said; that is the quintessence!
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Old 17th February 2012, 12:20 AM   #180
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well.. if nonswitching target is thermal stability, thermally coupled NTC/PTC or diode is the best, because it does not affecting amplifier performance at all.

That I like from this technique is it canceling crossover distortion, not rejecting, or reducing by NFB. Principle of 2 diode crossover gap (mosfet in AR D400) added to input to cancel crossover distortion of output.
for canceling principle:[ error - error = eliminated ] then, [ crossover distortion - crossover distortion = no crossover distortion ].
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