Crossover - hard to find for biamping

Wait

You shouldn't need a crossover if you are using the existing built in crossovers just volume controls.  It might get tricky if the amps have a different gain profile as you adjust for one global  volume level and then if you increase or decrease the volume the bass amp and the mid tweeter amp are no longer in sync.  It may not be much of an issue as you can always just increase one of the amps volume level to compensate.

If you're thinking of leaving the frequency dividing to the internal passive x-overs and using the active x-over just for level control you may not need one. If you choose tube and SS amps with the same gain (e.g. 26db) they should power the drivers to matching levels (even if they have different power ratings). Perhaps other, more technically minded members can verify my thinking. Then you would simply have to "Y" the L and R outputs of the preamp into the two sets of amps. Generally, the less electronics the signal has to pass through, the better.

I doubt you will get much value out of this configuration.  Active biamping can be very rewarding with an active crossover and bipassing the passive ones in the speakers. Leaving them in, well all you are doing is combining amps. 

jji666

If the speakers have separate binding posts for low/mid-hi and any jumpers are removed then the amps will not combine. The low amp will drive the woofer via the internal low pass network and the high amp will drive mid/hi via high pass-separate paths. Assuming they are good speakers then a lot of thought and design went into tailoring those internal x-overs for the drivers. Additionally it would be a bit of a project to get inside cabinet and re-solder wiring to by-pass x-overs. The SS low amp will have good low frequency extension and control of woofers and the tube amps will give their tube magic to mid/tweets.