Erik and George are of course correct that impedance compatibility needs to be carefully considered in this situation, given that preamp-to-power amp impedance incompatibilities tend to arise most often when tube-based preamps are used in conjunction with solid state power amps, and given that in this case the preamp would be driving two power amps.
However, given the following statement in this thread I think there is a good chance that the Rhumba 1.2 Extreme would be suitable in that respect:
The 75 ohm figure is most likely based on a mid-range frequency such as 1 kHz, and is probably a good deal higher at 20 Hz, but this statement nevertheless appears to suggest that the match stands a very good chance of being suitable.
Regarding the LS27, the 8008 MkII is spec’d as having an input impedance of 46K single-ended and 70K balanced (which probably means 35K per leg), and while various versions of the Palladium have low single-ended input impedances (for versions which provide single-ended inputs), their balanced input impedances are in the vicinity of 44K (which probably means 22K per leg). The ARC LS27, like most ARC line stages and preamps, has a recommended minimum load impedance of 20K, although it is not clear if that applies to the single-ended outputs, or to the balanced outputs, or to each leg of the balanced outputs. 70K in parallel with 44K is 27K, while 35K in parallel with 22K is 13.5K. So it is possible that the LS27 would be a suitable match if you were to drive both amps with its balanced outputs, via XLR splitter cables, and depending on how ARC’s 20K minimum load recommendation is defined. And the match might also be within reason (although not ideal) if you were to drive the 8008 MkII with the LS27’s single-ended outputs while driving the Palladium with the LS27’s balanced outputs (the resulting load impedance in that situation on one of the two signals in the balanced signal pair probably being 46K in parallel with 22K, which is 14.9K).
Good luck. Regards,
-- Al
However, given the following statement in this thread I think there is a good chance that the Rhumba 1.2 Extreme would be suitable in that respect:
BackertLabs 8-17-2018
... the Rhumba 1.2 preamp has an output impedance of less than 75 ohms, which is quite low. It allows the Rhumba to mate nicely with any power amp you might select. Thanks again and please don’t hesitate to write us, or call if you have any questions.
-Andy Tebbe
Backert Labs
The 75 ohm figure is most likely based on a mid-range frequency such as 1 kHz, and is probably a good deal higher at 20 Hz, but this statement nevertheless appears to suggest that the match stands a very good chance of being suitable.
Regarding the LS27, the 8008 MkII is spec’d as having an input impedance of 46K single-ended and 70K balanced (which probably means 35K per leg), and while various versions of the Palladium have low single-ended input impedances (for versions which provide single-ended inputs), their balanced input impedances are in the vicinity of 44K (which probably means 22K per leg). The ARC LS27, like most ARC line stages and preamps, has a recommended minimum load impedance of 20K, although it is not clear if that applies to the single-ended outputs, or to the balanced outputs, or to each leg of the balanced outputs. 70K in parallel with 44K is 27K, while 35K in parallel with 22K is 13.5K. So it is possible that the LS27 would be a suitable match if you were to drive both amps with its balanced outputs, via XLR splitter cables, and depending on how ARC’s 20K minimum load recommendation is defined. And the match might also be within reason (although not ideal) if you were to drive the 8008 MkII with the LS27’s single-ended outputs while driving the Palladium with the LS27’s balanced outputs (the resulting load impedance in that situation on one of the two signals in the balanced signal pair probably being 46K in parallel with 22K, which is 14.9K).
Good luck. Regards,
-- Al