Audio Note DAC Output Transformer Hookup
I've had some honkin big Audio Note Output Transformer's sitting on my desk destined for my AN DAC1.2 for some time and am attempting to add these to the analogue output stage of the DAC.
Instructions I culled from Audio Note kit enthusiasts included (most of the original analogue board being gutted):
- connect plate, grid and cathode halves of valve (in this case, a 6922)
- "black" wire from OT to high voltage
- "red" wire from OT carrying high voltage to plate (pins 1,6)
- signal to grid (pins 2,7)
- bias cathode (pins 3,8) to "+" of (2 in parallel) AA nickel metal hydride batteries, “-” to ground
- "orange" wire from OT to RCA signal (output to pre)
- "blue" wire from OT to RCA ground
- "green" wire from OT to chassis ground
- FIL+ to pin 5
- FIL- to pin 4
- pin 9 to ground
When first attempted on the original kit PCB (cutting required tracks), plate voltage was half what it should have been @ 50V. So I simply wired the circuit on a blank PCB. Now the plate voltage measures 200V (it's 215V off the power supply board) - but we want this to be 100V.
Any ideas? Not sure if the battery bias setup above is correct. Also the signal has a 470R to ground and 220R (grid stopper?) to grid. FIL+ is 6.15V
I'm just doing things by rote here so any advice or direction would be most appreciated.
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