You’re welcome, Ohlala.
However output impedance rises to 3.35K and 7.7K at 20 Hz are fairly extreme, and are definitely not consistent with "high current drive capability" that can handle any "real world load." Also, the line level input impedances of many and probably most powered subs are rather low, often between 5K and 20K. The lack of independent buffering for the two preamp outputs will put the input impedance of the power amp in parallel with that impedance, for the signal that is common between the RCA and XLR connectors, resulting in an even lower overall impedance as seen by the preamp.
The ML2.x amplifiers that you mentioned in connection with biamping have a considerably higher input impedance than most subs have, at 41K. Driving two of them with the same signal would result in a load impedance of 20.5K, which is marginally acceptable in relation to an output impedance of 3.35K. (Note John Atkinson’s comment in the measurement section of Stereophile’s review that "the Lamm L2 should not be used with power amplifiers having an input impedance of less than around 22k ohms if the low frequencies are not to sound lightweight"). Although the **difference** in the load impedances presented to the two signals on the XLR connector might in itself adversely affect sonics, since it would unbalance the balanced signal pair to some degree.
As I said earlier there’s no harm in trying such an arrangement. But unless the sub you choose and your power amps both have relatively high input impedances, such as 47K or more, the impedance issue could very well result in adverse effects on the sonics of both the sub and the main speakers. If so, you may want to consider putting some sort of buffer stage between the preamp and the subs, that would present a high input impedance to the preamp while driving the subs with a low output impedance.
Another member here faced a similar situation a few years ago with his ARC Ref electronics and a sub. A gentleman named Tom Tutay, of Transition Audio Design in Florida, custom made a suitable buffer stage for him at modest cost (hundreds of dollars, not thousands), which worked out very well. I don’t think Tom has a website, but his contact info can be found via a Google search.
Good luck. Regards,
-- Al
However output impedance rises to 3.35K and 7.7K at 20 Hz are fairly extreme, and are definitely not consistent with "high current drive capability" that can handle any "real world load." Also, the line level input impedances of many and probably most powered subs are rather low, often between 5K and 20K. The lack of independent buffering for the two preamp outputs will put the input impedance of the power amp in parallel with that impedance, for the signal that is common between the RCA and XLR connectors, resulting in an even lower overall impedance as seen by the preamp.
The ML2.x amplifiers that you mentioned in connection with biamping have a considerably higher input impedance than most subs have, at 41K. Driving two of them with the same signal would result in a load impedance of 20.5K, which is marginally acceptable in relation to an output impedance of 3.35K. (Note John Atkinson’s comment in the measurement section of Stereophile’s review that "the Lamm L2 should not be used with power amplifiers having an input impedance of less than around 22k ohms if the low frequencies are not to sound lightweight"). Although the **difference** in the load impedances presented to the two signals on the XLR connector might in itself adversely affect sonics, since it would unbalance the balanced signal pair to some degree.
As I said earlier there’s no harm in trying such an arrangement. But unless the sub you choose and your power amps both have relatively high input impedances, such as 47K or more, the impedance issue could very well result in adverse effects on the sonics of both the sub and the main speakers. If so, you may want to consider putting some sort of buffer stage between the preamp and the subs, that would present a high input impedance to the preamp while driving the subs with a low output impedance.
Another member here faced a similar situation a few years ago with his ARC Ref electronics and a sub. A gentleman named Tom Tutay, of Transition Audio Design in Florida, custom made a suitable buffer stage for him at modest cost (hundreds of dollars, not thousands), which worked out very well. I don’t think Tom has a website, but his contact info can be found via a Google search.
Good luck. Regards,
-- Al