restorer-john
Grand Contributor
Is the headphone amp on this an add on op-amp chip on the preamp, or is it taken off the power amp?
It apparently has a separate amplifier for cans. Probably a low impedance gain/buffer stage parallel to the pre-amp out.
This is a good idea with an integrated amplifier as the power stage residual noise would otherwise be audible in sensitive headphones. Also, typical vintage implementations use medium value (220-2kohm+) resistors (4) to safely drop the massive voltages (and consequent power) of a power amplifier stage. Trouble is, those resistors create a very high source impedance with subsequent changes to the FR of the connected cans.
The old Sony VFET amps had great headphone amps that were part of the amplifier circuitry.
The Sony VFET series, TA-3650, 4650, 5650 and 8650 all implement headphones as I outlined above. Here is the 8650's connection and they are all essentially identical.
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