Gain matching of power amps

Miketw and Edesilva: Neither of you mention whether you have considered using an active crossover, which I consider the best way to do biamping. The individual speaker drivers should not really be receiving the full frequency range from the respective amps driving them. The overall goal of biamping is to split up the signal after the source/preamp and send a limited range of frequencies to the appropriate amp and then driver.... bass signal (say <200Hz) to the bass amp and then directly to the woofer, etc. Another advantage of the active xover unit is that most allow volume adjustments, so that the signal level going to each amp can be can equalized. This helps some with the gain issue, but as Herman has nicely outlined, you still don't want amps of wildly different gain involved. By the way, I'm not convinced that it always works to have SS for bass and tubes for mid/highs, since some speakers reveal the sonic differences between such amps at the crossover point. Some experimentation is obviously required for each case.

Thanks for the info, I'm still thinking about what to do when I move in 1.5 mo. and can unpack some gear in boxes, and its food for thought. Martin Logan actually recommends bi-amping my Prodigys with tubes up top and SS below. I was going to use a pair of ARC VT100s I have, but now am thinking of watching for an old ARC D400 and using the extra VT100 elsewhere.

In my case, Ral, the Casablanca can be turned into an active x-over. All things being equal, however, I'm not inclined to go active b/c I'm not sure I can replicate the job the ML x-overs are doing and the marginal volume doesn't really mean that much to me.

I always thought the "purists" suggested avoiding an active x-over anyway to eliminate "yet another thing in the signal path"... (Obviously, doesn't apply in my case, 'cos the Casablanca is there anyway).

Edesilva: I didn't know that about the Casablanca... interesting. I see your point about not trying to recreate the ML crossover. And yes I think many purists want to avoid any signal processing between source and amp, and this is quite reasonable. However, in a few cases a good active xover can actually improve things if the speaker's passive xover system is not so great (that was my case with the Maggie 3.6R factory bass-to-mid xover box). A Marchand xover (deluxe version with upgraded parts) has worked well for me and introduces negligible sonic signature given the overall improvement from biamping. I've read that the Bryston xover is pretty neutral too. Probably there are other good ones.

Many thanks for the responses. Especially Herman, level of detail I wanted, and much appreciated. I have two matching power amps right now, so I know that this is the best gain match solution. May need to look at other alternatives to resolve tweeter problem. Currently using runs of Stealth Premier for both tweeter, and woofer. Maybe should look for a softer/darker cable for tweeter, recommendations?.
What is your view of going to a more powerful amp, and NOT bi-amping at all. Candidates, Classe 150/200, McCormack DNA 1/2, Audio Research D240/400?. Other recommendations? Would probably still want to biwire.

Sorry to take a step backwards here, but the difference between using a good quality active crossover and bi / tri / quad amping and passively multi-amping with passive crossovers is STAGGERING to say the least. More "junk" in the signal path ( active crossover ) will almost always produce results that you've never dreamed of if you have the time and know-how to dial it all in. However, you do have to take the passive crossovers out of the speaker circuit, resulting in "direct drive" from amp to speaker. MUCH, MUCH better. Sean
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