[topround]

Ok crazy question, but what are the correct set of parameters that would make a setup like tubes on top and solid state on the bottom, work, correctly.
I imagine the input impedances should match between the two amps but what about gain, and damping factors and any other issues I should be aware of. I have bi amped in the past in this fashion, but not by design, just with what I had at my disposal at the time.
If I were to plan a system like this what should I look for in matching amps?

Thanks all
Mike

[toobluvr]

Ok crazy question, but what are the correct set of parameters that would make a setup like tubes on top and solid state on the bottom, work, correctly.
I imagine the input impedances should match between the two amps but what about gain, and damping factors and any other issues I should be aware of. I have bi amped in the past in this fashion, but not by design, just with what I had at my disposal at the time.
If I were to plan a system like this what should I look for in matching amps?

Thanks all
Mike

At a minimum, amp input sensitivities should be the same.  If not, gain imbalances will occur.
That is, the amp that is more sensitive (ie: has a lower input sensitivity) will be louder at a given preamp volume control setting, and your sound, lows vs highs, will be out of balance.

If amp sensitivities are different, it is not insurmountable.  If passive biamping, the more sensitive amp (ie the louder one)  must have a built in volume control on its inputs so it can be turned down relative to the other one.

If actively biamping, the external crossover should have built in volume controls to handle amp gain differences.

Input impedances on each amp do not need to be identical.  Each amp must adhere to the general ratio rule so that frequency response anomalies will not occur.  I think to be safe, the ratio of amp input impedance to preamp output impedance s/b 50x or greater.  Not 100% sure on this exact ratio....those more technical than I can chime in here.

After this, I think your ears will tell you if your choice of amps is "right" or not.

[flintstone]

Another problem you can run into (at least I have) is the crossover freq"s involved....If you try to blend a SS amp with a tube amp, smack dab in the middle of vocal ranges...the transfer is not always, as smooth....as it would be using the same amps, or...at least amps that are "like" in sound.

IMO, the lower the crossover point....the better.


Dave

[oris98]

I have discussed biamping issue with one of the well know audio cable manufactorer before and his opion is that biamp may causing incorrect phase matching the speakers are driven by different amps and speaker cables.  If the signal going from the upper amp is slower (I am talking million seconds) reaching the tweeter then the signal going from the lower amp or the other way around (either due to the response from the amp of speed or the cable, this is particularly true for tube amps), their will be a phase mismatch situation between the HF and LF as both the woofer and tweeter are not being pushed or pull in the same time and becomes the diaphrams are not being moved at once...  The sonic degradation may varys from situation to situation.  His suggestion is biamping with the same amp and with same speaker cables to prevent this problem.