What you are proposing is known as passive bi-amping. If your NAD pre does not have two sets of outputs, then you will need to utilize some form of "Y" splitter, or have interconnects built with a "Y" split. This will allow you to hook both power amps up to your pre-amp simultaneously. There are basically two different methods for passive bi-amping. One is Horizontal bi-amping the other is called Vertical bi-amping. Horizontal bi-amping is usually the preferred method. With Horizontal bi-amping one amplifier will power the high frequencies of both speakers while the other amp will power the woofers or bass section of the two loudspeakers. Vertical bi-amping is accomplished by having one amplifier driving the highs and lows of one speaker while the other amp drives the highs and lows of the other speaker, almost like mono-blocks but with the amp remaining in stereo mode, one channel of each amp will be hooked up to the highs and the other channel will be hooked up to the bass of each speaker. This is an effective way to add some headroom to your system. Some even feel that passive bi-amping has other sonic benefits, but my personal experience with it has yielded only higher output not better sound. That's okay higher output is the goal here,right? Try both methods and see which one you like best. If the Adcom amps are bridgeable this would be the course of action I would recommend as it will offer even more power than passive bi-amping, plus you will not need any "Y" adapters or cables.If your budget was ever to permit, I would highly recommend selling the Adcom power amp, purchasing a Linn power amp and later adding a second Linn power amp with some cards for active bi-amping. Active bi-amping, using electronic crossovers to re-direct the appropriate frequencies to the appropriate speakers and drivers, is a whole different kettle of fish from passive bi-amping and will provide a large increase in sound quality. Linn has been proponents of, and have offered active bi-amping options for most of their speakers for sometime now. I have heard Linn active set-ups compared directly to the identical passive set-up and there is no comparison. The active system wins on all counts. Much better defined and lower bass, wider and deeper soundstage, higher power handling and SPL, and the list goes on and on.
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Adding the 2nd Adcom amp and bi-amping (horisontally or verically - you will experiment with that) is the cheapest solution.
You are probably much better off by selling your Adcom and as suggested above buying Linn power amplifier (or similar).
By-ampling is only good when your amps cannot deliver required current into low frequency area . In such a case your treble/middle range will be undistorted. Human ear is much more sensitive in that area and not in bass area.
Otherwise one amp (single ended or fully balanced) is better.
I use two Pass ALEPH 30 for passive vertical biamp.
With this biamp. type you will have better channel separation and less distortion, but only increase the power in 3db.
If you need more power, go with a bigger power amplifier.
Remember that you have to add an extra Interconnect cable for biamp. and your speaker cable must be prepared for it.
Hope this help you.
You'll find this post by the noted designer Steve McCormack to be well worth reading.
Also, I believe that contrary to widespread belief the 3db power increase (i.e., twice the power) that is commonly cited for bi-amping vs. single amping will in many and probably most cases not be realized. In the common situation where power delivery of the single-amp arrangement is limited by voltage swing capability (i.e., by clipping, as opposed to being limited by the amp's output current capability), the power increase provided by bi-amping will be 0 or close to it.
For equal volume to be produced in the bi-amp'd configuration vs. the single-amp'd condition, the two bi-amp'd amps will both have to output the same voltage swing as a single amp would have to. So the volume level at which the clipping point will be reached will not be changed by bi-amping, other than to the extent that the available voltage swing capability of the particular amp design may vary as a function of current demand (although that may be significant in many cases).
What will be helped is that the amount of current each amp channel has to supply will be reduced, which may improve the sonic performance of the amp even if it would not enter current limited conditions in the single-amp configuration. Also, vertical biamping will provide the benefits Steve describes in the post I linked to, eliminating crosstalk across the common power supply and ground system that can occur to some degree with some amps in single-amp or horizontally bi-amped configurations, since in those configurations the two amp channels handle different signals.
With "passive" biamping each amp must swing the peak-to-peak voltage of the full range signal, so, as Almarg says, no significant power increase will be realized.
On the other hand, when you use an electronic crossover (real biamping) at a given total signal level, the peak-to-peak voltage swing of each amp is reduced. The high frequency signal does not ride on the Low, and vice versa.
Some increase in total power will be realized.
However, the greatest benefit of real biamping is the reduction of IM distortion. This was more important years ago when amps commonly exhibited more than 1 percent IM distortion.
Vertical bi-amping will most likely give you your biggest bang for the buck. You will need another 60 watt Adcom identical to the one you have now.
This method was used by Richard Vandersteen at the shows using two Classsic 30s to drive 2Cs with excellent results.
Vertical bi-amping should give you the more relaxed sound you are looking for.
Thanks everyone. I made a typo and wrote "bi-wire" when I meant bi-amp, but it would seem everyone caught it.
Broad range of responses here. One of my closest friends has a tri-amped complete Linn system with Aktiv speakers, and I agree, the results are stellar.
I got it in my head to get a second MA, which I'm about 2/3's finished with, so bigger upgrades should be possible in a few years.
Having said that I sort of enjoy looking for a sound I like by hunting around for good deals.
My little Adcom doesn't appear capable of chaining, as there are no outputs to connect interconnects to another amp. That means it cannot be use for bi-amping, right?
Likewise, while my NAD preamp's manual says it can work with multiple amps, it only has two sets of outputs for the amp, one which is labeled "high" and would seem is only for using with specific speaker types.
I would need both a different amp and preamp to make bi-amping possible, right? Looks like many feel the easiest solution is to just upgrade to a more powerful and higher end amp.
Again, the little Adcom sounds great at any normal volume, but if being driven hard seems to get a tad harsh. I'd like to eliminate that.
Thanks again- sorry I'm all over the place.
I had a pair of Sim Audio amplifiers which I bridged mono hooked up to a pair of Alon V MKII speakers. liked it well enough but wanted to try tubes. I bought a used pair of Cary V12r amplifiers and have been running them horizontally bi-amped. Am very happy with all aspects of the sound- never feel the need to switch to ultralinear, which I feel slightly degrades the overall sound. An improvement to my ear over the solid state Sim Audio. Don't know if the bi-amping contributed much to the result- too satisfied to screw with it- for now.
my recomendaton-if the other amp is cheap enough- buy it- play with it- see what it does for you. Your the only one who has to be happy with it.