Gain matching of power amps

Herman, I bet your opinion of me is bolstered when i agree with you : ) I bet that there are a lot of others that wish i would shut up :(

Honestly though, it's good that you and a few others take the time to present "details" and "formulas". It gives many of the others a good idea of what it takes to make this stuff tick and how engineers do their work. As mentioned, it is science that has gotten us this far in audio reproduction and forgetting that might be a grave mistake. Sean
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Kudos to you guys, you answered a question that I had in a different post. But, let me see if I've got this right.

I've got a Casablanca preamp, which is basically a big Theta card cage that you can slap different D/A output cards in and configure each output the way you want. I think (I don't have my manual here) that you can pre-set a gain for each output, so output set A could be configured with, say, 3 dB of additional gain over output set B, at 0 dB gain. If I then had an amp X with a gain of 26 dB and an amp Y with a gain of 29 dB, would I then achieve a uniform gain of 29 dB by hooking amp Y to output B and amp X to output A?

The reason I ask is because I always assumed that there was some nonlinearity in the gain as you increased the input voltage. I.e., that the gain you find in the specs is some average and is not a constant over the range of input voltages. Is this a dumb question?

Gain is gain, it is constant no matter what the input voltage (until clipping, that is). So yes, in theory your hookup would work. The only caution has to do with tolerances, i.e., is the gain exactly 29.0 dB or is it actually 28.2 dB? Same goes for the other amp. You would need a high quality calibrated voltmeter to be certain.

Edesilva, you are correct. Gain in dB is additive so your math is correct. You are also correct about amplifiers being nonlinear. However, a well designed amplifier will keep this non linearity to a small fraction of a dB and shouldn't be of concern.

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.