Bi-amping vs. bridging

Gah, I meant to say:

The increase in the minimum impedance requirement when bridged is related to the maximum safe thermal dissipation of the amplifier, in watts.

This is the same reason why most power amps won't support 2 Ohms. The power dissipation needed would cause a thermal meltdown. Hopefully your amp will shut off before this happens! 

Best,

E

I appreciate the input from everyone. It sounds like I will stick to the bi-amping, especially with the 4 ohm ML's.  I have plenty of amp channels available, it should just be a matter of getting the right signals from the pre to the amp(s) from what I can gather.  What would the cons be for splitting the front L/R outputs at the preamp to provide the signal into the amp?  Is this also an impedance consideration?

What would the cons be for splitting the front L/R outputs at the preamp to provide the signal into the amp? Is this also an impedance consideration?

I suspect that won’t be a problem in this particular case, although I can’t say that with certainty because the output impedance of the AV-7005 is not specified.

As I mentioned earlier, driving two amplifier channels from the same preamp or prepro output stage will result in the preamp or prepro seeing a load impedance equal to the input impedance of the amp divided by two. Your Rotel RKB-650 amp has a specified input impedance of 20K, so two amp channels in parallel would present a load impedance of 10K. That would be a problem for many tube-based preamps, and for at least a few solid state components, but I suspect it would be ok in this case.

Also, to minimize the cable capacitance that would be seen by the prepro it would be preferable to split the signal using short y-adapter cables connected to the amp inputs, in conjunction with a single RCA cable for each channel, rather than splitting it at the outputs of the prepro and running two RCA cables for each channel. Although given the short lengths of the interconnects that appear to be required in your setup it probably won’t make much if any difference either way.

Regards,
-- Al

I really appreciate you help, Al.  I think I am going to experiment with using the Front High outputs to use as the source signal for the tweeters.  This assumes the signal will be the same as the Front's.  It would then eliminate the potential impedance/loss issues of splitting the signal from just the Front.  I'll probably give that go tonight and post the results here for reference.

Follow up:  I tried the Front High pre-outs as the source for the tweeters on the mains, and I was disappointed.  They sounded very muted and did not present musically as I had hoped.  Now, that being said, I was using the pre in stereo mode, so I presume there was some 'non-processing' going on if you will.  When I went to the All Channels selection, they did seem to wake up and became, at least to my non-audiophile ears, much brighter and clearer.  Again, I suspect it is a processing matter, so for the time being, I have returned to splitting the front mains into 4 channels for amplification sine I prefer to listen to my music in stereo mode.