Is equal gain OK for bi-amping?

For the output signals of both amps to be the same level, the input sensitivity of both amps must be the same and the gains must match also. Other characteristics also factor into this, but these two are the important factors. If the gains are the same, but the input sensitivity is different, then the output levels will not match for the same signal input. You "May" hear a gap or hole between the upper registers and the lower bass. Borrow an amp from a friend or dealer to use for a week or so before buying one to see if this is something you want to do or if another amp will work. An active crossover works wonders in this circumstance, and they have input matching or gain controls also.

enjoy

Hi Koestner, I would second what Minorl said. I am running a Marchand active crossover and bi-amping with a valve amp on top and a SS Class A/B amp on the bottom. The advantage of doing this is that the valve amp does not "see" any bass frequencies, so its apparent power is higher.

The downside of using an active crossover is that the slope of the crossover will sum with the internal passive crossover of your speaker, resulting in a steeper slope and possibly introducing phase issues. Ultimately the best solution is to go fully active - bypass your speaker's internal crossover and connect the amp directly to the drivers with an external active crossover in place.

You can do this upgrade in stages (which is what I did). Start off by bi-amping, then add the active crossover later.

Oops, seem like I forgot input impedance has to be the same also. Well that makes it a lot harder to do. Maybe I will get an integrated tube amp and adjust the volume until it sounds right on both top and bottom.

Will I really be wasting the power the upper amp makes in bass notes if the speaker's crossover blocks them, doesn't the speakers crossover create a much higher impedance at bass frequencies thereby not alowing the upper amp to waste that energy?