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I'm involved in a discussion on another list regarding to what degree the speaker field-coils in some Hammond Organs work to reduce power supply ripple.
I'm attaching a schematic of the model M-3. The speaker field coil is in series with the ground-return of all but the first filter capacitor stages, and it's used, in part, to obtain the negative bias voltage for the output tubes. My intuitive sense is that, in this arrangement, the field coil provides some degree of power supply ripple filtering, but not quite as much as you'd get if it were part of a conventional pi-filter in series with the B+ supply.
In other words, I think Hammond achieved three objectives here: 1) powering the speaker field, 2) deriving a negative bias voltage, and 3) obtaining some power supply filtering. But I think that the power supply filtering aspect is slightly compromised by its position in the circuit.
The guy arguing against me says that the field-coil provides *exactly* the same degree of power supply filtering that it would if it were part of a typical pi-filter in series with the positive supply.
I'm happy to be told I'm wrong, if I am, but I need a fresh pair of eyes.
I'm attaching a schematic of the model M-3. The speaker field coil is in series with the ground-return of all but the first filter capacitor stages, and it's used, in part, to obtain the negative bias voltage for the output tubes. My intuitive sense is that, in this arrangement, the field coil provides some degree of power supply ripple filtering, but not quite as much as you'd get if it were part of a conventional pi-filter in series with the B+ supply.
In other words, I think Hammond achieved three objectives here: 1) powering the speaker field, 2) deriving a negative bias voltage, and 3) obtaining some power supply filtering. But I think that the power supply filtering aspect is slightly compromised by its position in the circuit.
The guy arguing against me says that the field-coil provides *exactly* the same degree of power supply filtering that it would if it were part of a typical pi-filter in series with the positive supply.
I'm happy to be told I'm wrong, if I am, but I need a fresh pair of eyes.
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