Splitter -- One preamp to two amps. What to use?


I need your help! If people are bi-amping, How are they connecting from their preamp to their two amps and to their speakers?

I am currently running my NAD 1700 preamp with two separate outputs. One is a Lab unfiltered RCA out which goes to my Mid’s and Highs into one of my NAD 2600 amps. And I have a second RCA Normal, which is lower fidelity which runs thru another NAD 2600 into my woofers. I then run two sets of 10 gauge Blue Jean cable to each speaker. What I would like to do us upgrade my speaker wire ( AudioQuest Redwood or DR Acoustics Red Sky Bi wire ) which are bi-wire cables and bridge my amps to achieve 450 watts per channel.

Here is the problem. In order to do this I need to split the one output from the Lab RCA on my preamp to feed the two separate amps. I am currently using Audioquest Waters and hate to put something inline that is a lower quality than the Waters.

I can’t believe I am the only one with this problem. How are the smart audiophiles addressing this problem?
captaindidactic
I was just about to post the following when I saw MrDecibel’s post above. Great minds think alike :-)

In most cases a bridgeable amp will not sound as good in bridged mode as in stereo mode. A major reason for that is that in bridged mode the amp will "see" a load impedance equal to the speaker impedance divided by two. And in this case it appears that the NAD 2600 is specified to drive impedances of 4 ohms minimum (in stereo mode), so if the impedance of your speakers is less than 8 ohms, or if it has a nominal impedance of 8 ohms but dips down to significantly lower values in the bass or mid-bass regions (where lots of energy is often required), that issue is likely to be particularly significant.

Also, like many NAD amps your 2600 has considerable dynamic headroom, and is specified for stereo mode as being able to provide short (20 millisecond) bursts of at least 380 watts into 8 ohms and 450 watts into 4 ohms. So the power increase that bridged mode can potentially provide (if the impedance of your speakers is not too low) is unlikely to be needed anyway.

I suspect that a better approach would be to change from the present "horizontal" biamp configuration you are using to a "vertical" biamp configuration. In that configuration the amps would be used in stereo mode, but each amp would be dedicated to a single speaker. One channel of one amp would power the highs on one speaker, and the other channel of that amp would power the lows on the same speaker. When two identical amps are biamped a vertical configuration is generally considered to be preferable to a horizontal configuration. The reasons include reduced inter-channel crosstalk within the amp (since both channels process the same signal); the power supplies in the amps just need to support bass frequencies (which typically require a lot of energy) for one channel rather than for two; and a vertical configuration may make it possible to locate the amps close to the speakers, in which case both the sonic effects and the cost of the speaker cables may be reduced as a result of their shorter length.

What I would suggest is that you consider implementing a vertical biamp configuration by putting a short y-adapter cable at the inputs of each of the amps, and for each channel running a single interconnect from the higher quality output of the preamp to both channels of the corresponding amp, via the y-adapter. Looking at the impedance numbers for the amp and preamp in this particular case there will not be an impedance compatibility problem, if a single preamp output is used to drive two amp channels.

Good luck. Regards,

-- Al

You guys!  What perfect responses! Thank you! I guess now my only concern is the possible degradation of signal flow at the y-adapter. I'm running audioquest Waters interconnects and would hate to lose the quality at the Y. Suggestions? Female input into two male outputs takes wire. 

Michael
Captaindidactic, I’m running the same setup as Al and Mr Decibel mentioned, vertical bi-amp with a NAD 1600 feeding a pair of 2700 amplifiers. The 1600 and your 1700 can easily drive several amplifier input stages as they have significantly higher input impedance than the output impedance of the preamp/tuner. I make my own cables, but haven’t gotten around to building the required Y cables, so for now, I’m just using “good” cables with a pair of BNC tees and RCA adaptors as a temporary stopgap. My 1600 has a bit of distortion from the solid state switches that are used for source selection, so actually at this point, I’m using a 3225PE as a preamp only feeding the 2700 amps, which power my Energy Reference Connoisseur 30 speakers. This setup sounds fantastic. The power amps get pretty warm, so be careful to ensure they have good airflow through the heatsinks and there isn’t any accumulation of dust and debris. 
@Captaindidactic, I wouldn’t be too concerned about the choice of y-adapter. Just get whatever strikes your fancy that appears to be of good quality and is not much longer than necessary.

First, keep in mind that most cable parameters, and therefore presumably the degree of most cable effects, are proportional to length. Second, while there have been more than a few reports here to the effect that "splitters degrade the sound," my belief is that in most of those cases the reported findings result not from the splitter itself, but from some combination of several factors that would not apply in your situation. Namely impedance incompatibilities that can arise when a splitter is used; ground loop effects that can sometimes occur when an output is used to drive two separate components; and increased loading of outputs by cable capacitance, that can result when an output is split and is used to drive two lengthy cables.

Good luck. Regards,
-- Al