Stereo pre-amps with dual outs for bi-amping and a subwoofer line out

My McIntosh C2500 preamp has 3 separate pairs of outputs both single ended and balanced.

Audio Research.

A point to be aware of is that most preamp and line stage designs which provide two pairs of RCA outputs drive both of them from the same output stage, and simply jumper the two connectors for each channel together inside the rear panel. And likewise for designs which provide two pairs of XLR outputs. From an electrical standpoint that is essentially the same as using a good quality splitter on a single output.

Also, in many (but not all) designs providing both RCA and XLR outputs the signal provided to the RCA connector is the same signal that is provided to one of the two signal pins on the XLR connector.

All of that applies, for example, to most Audio Research line stages and preamps.

And what that means is that the output stage of the preamp will see a load impedance equal to the parallel combination of the input impedances of the two power amps, which will be considerably less than the input impedance of either, and may be too low to be optimal for some preamps. For example, Audio Research recommends a **minimum** load impedance for most of their line stages and preamps of 20K. If say one amp has an input impedance of 30K and the other has an input impedance of 50K, their combined input impedance would be (30 x 50)/(30 + 50) = 18.75K, too low to be optimal.

FWIW, I have used the Audioquest splitters Yogiboy suggested in applications involving suitable impedances with fine results.

Finally, keep in mind that most powered subs have relatively low input impedances for their line level inputs, typically somewhere between 5K and 20K.

Regards,
-- Al

Thanks all for the comments and suggestions. I'm currently running a split signal with Audioquest, just looking for something a little more elegant and I suspected I wasn't looking in the right price point.

Not quite ready to put $3 to $5k down on DEQX, Anthem or Parasound pre, but I'll certainly keep my eyes peeled.

I find it interesting that in a world full of bi-amp + speakers, most stereo preamps leave the solution out of their equipment. But Al seems to have hit the answer on the head. And stereo preamps are dinosaurs nowadays despite being some of the most satisfying/frustration-free listening experiences. 

I see that zero tube preamps are represented here!

Also, I was honestly surprised to see Anthem on the list, I thought they went out of business, guess they just went out of the tube business. Good for them, glad they are still here. The business sure has had to change. Used to be 4 hifi shops in my town, all carrying different brands. Now I've got to travel 120 miles round trip to reach 4 dealers.

My tubed Schiit Freya has 2 single ended and one balanced out. The 2 single ended outs go to my main tube amp, and a generally not in use SS amp for "remote" speakers. No impedance issues noted, and turning the "remote" amp on has no audible effect on the main amp whatsoever.