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Old 13th July 2007, 12:03 AM   #11
jnb is offline jnb  Australia
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Oh, I thought the aikido was an SRPP with an active CF after it

Anyway, I don't much like the sound of an SRPP at low levels, myself. Not sure why.
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Old 13th July 2007, 12:14 AM   #12
SY is offline SY  United States
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The point of the Aikido is the symmetry between top and bottom halves. In the SRPP, you take the output from the upper tube's cathode, and the lower tube might have the cathode resistor bypassed (the upper tube is degenerated by the cathode resistor). LED biasing on the bottom is equivalent to a near-perfect bypass. Source impedance is relatively low, rendering a follower stage moot.

In the Aikido, the two halves are degenerated identically and the output is taken from the bottom of the upper tube's cathode resistor, the exact halfway point. The integral follower is then necessary to maintain that symmetry. As part of John's quest for maximum supply rejection, the follower is fed the power supply noise in antiphase to achieve cancellation. All of those features are not present in jerluwo's circuit.
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