Thanks, Hifigeek. Jdolgin, descriptions I found of the VM220 indicate pretty clearly that it is fully balanced. However, as Hifigeek's comments make clear, the fact that it is a tube amplifier having an output transformer introduces still more variables and unknowns into the already "confusing mess" which you aptly described.
I've seen some older ARC schematics, such as this one for the fully balanced VT130, showing circuit ground as being connected to the 4 ohm output tap of the amp, rather than the common (black) terminal, and with circuit ground and chassis ground being connected to each other through a 10 ohm resistor.
*If* Hifigeek determines that the design of the VM220 is similar in those respects, I think that you could connect the black wire to the 4 ohm output terminal of the amp, and the red and yellow wires to the 8 ohm terminal.
Alternatively, assuming that is how the design is implemented, you could connect the black wire to the 4 ohm output terminal, and the red and yellow wires to the common (negative) terminal. Doing that would introduce a 180 degree phase reversal between the sound produced by the sub and by the main speakers, which you would correct for with the sub's phase reversal switch, assuming it provides one. Doing it that way would result in the sub receiving a somewhat (about 8 db) greater signal level than if you were to connect between the 4 and 8 ohm terminals.
But we'll see what Hifigeek determines.
Regards,
-- Al
I've seen some older ARC schematics, such as this one for the fully balanced VT130, showing circuit ground as being connected to the 4 ohm output tap of the amp, rather than the common (black) terminal, and with circuit ground and chassis ground being connected to each other through a 10 ohm resistor.
*If* Hifigeek determines that the design of the VM220 is similar in those respects, I think that you could connect the black wire to the 4 ohm output terminal of the amp, and the red and yellow wires to the 8 ohm terminal.
Alternatively, assuming that is how the design is implemented, you could connect the black wire to the 4 ohm output terminal, and the red and yellow wires to the common (negative) terminal. Doing that would introduce a 180 degree phase reversal between the sound produced by the sub and by the main speakers, which you would correct for with the sub's phase reversal switch, assuming it provides one. Doing it that way would result in the sub receiving a somewhat (about 8 db) greater signal level than if you were to connect between the 4 and 8 ohm terminals.
But we'll see what Hifigeek determines.
Regards,
-- Al