Bi-Amping 2 Interconnects or Y Cable?

I got my Y adaptor from Purist Audio Designs, I think in the $250-300 range, Origanaly had two runs of rca and like the sound better with the Y cons.

Perhaps Al can comment more on this but I see an issue with the simple y-adapter (been there, done that) you are going to use. When you connect both inputs of one amp to one pre out, you are changing the sensitivity because the input impedance of the amp is cut in half on each channel. I think Al was thinking on this when he mentioned the buffering on the pre outputs. This can change the sonic performance and behavior of the amps. So, next you need to get an active crossover between your pre and amps. Then all of the components see the load they were designed for. It is more money in cables and the crossover but the results are much better than what you'll get with a y-adapter. MY .02, YMMV, and all that.

Or! You could add shunt resisters on the amp inputs. ;-)

Hi Dan,

I don't see any problem there. Martin Colloms' measurements in the review I linked to indicate that the power amp's input impedance is 50K (although the quoted specs say 100K!). So the two channels in parallel will present to the preamp a combined load of 25K. That won't result in a significant reduction in sensitivity (or significant frequency response unevenness, either) with nearly all preamps, especially solid state ones such as Toby's MC-7, since the preamp's output impedance will be vastly lower.

The lack of separate buffering on the two output jacks also means that the two-cable approach Toby was considering would result in the preamp's output stage seeing nearly twice the amount of cable capacitance as with the y-adapter approach. That could result in perceptible upper treble rolloff if cable lengths are long, the cables do not have low capacitance per unit length, AND preamp output impedance is high. But again, in this case the output impedance of the preamp is most likely low enough for that to be a non-issue, regardless of which approach is chosen.

Best regards,
-- Al

Thanks, Al. I didn't mean to suggest a mis-match, only that IME it can change the sound, usually a reduction in bass impact.