Strange splitter in the Audio Research D4
Has anyone seen the AR D4 schematic? It's an all-balanced design that uses as a phase inverter a "preamp" to one side of the PP input stage. I've never seen anything like it before. It's too big to post here, it will have to be a link. It's that scruffy-looking ECC81 (12AT7) that's squeezed into the bottom left corner. :D
That is only a phase inverter with a gain of one.
At first glance, I thought it might be a 4th circuit inverter.
But its nothing so glorious.
1st half Y1 (ECC83) tries to -multiply input by Mu of 100
2nd half Y2 (ECC81) tries to cathode follow that Mu.
But the input and output feed together op-amp style
through the 301K and 316K resisistors to a unity (-1)
local loop gain.
Audio Research strikes again!
Thisi s absolutely nothing new, and about as complex and excessive as you can get.
KISS in reverse seems to be A-Rs claim to fame...
Looks like another clone of the Worthen phase splitter. It may provide good balance once set up with the right tube, otherwise a replacement will require test equipment to re setup. A major disadvantage. Not my ideas.
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