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
To do this correctly your preamp should be plugged into an active crossover like The JL Audio unit which would then have separate outputs for the woofer and treble amplifiers. This gives you control over the cross over points, phase and amplifier gain. 
I forgot to mention that you can also bypass part or all of the passive crossover in your speakers which in many if not most cases will improve the sound and imaging. 
yogiboy  
I thought about the Y adapter, but I am wondering if that will degrade the sound by putting in an inferior jumper in the middle of the line. 

mijostyn
Sounds Intriguing, But how do you bypass all the crossovers in the speakers? My big Acoustic Research TSW 910's are 6 way speakers. Also, from a purist standpoint ( fewest things inline is better ) How does an active crossover change the sound? Or is it like everything else...Try it and see??
Maybe I missed something, but if you are bridging your amps then why do you need a splitter at all? If I read it right, now you have 4 channels of amplification by running each amp in stereo, one for HF one for LF. If you bridge your amps to mono then you will only have 2 channels, that you can then bi-wire if you so desire.
You also need to keep in mind that in most cases using both preamp’s outputs at the same time running two separate but identical amps, will present half of one of the amp’s input impedance to the preamp. Depending on the preamp output impedance and the amp input impedance, e.g., ratio of 1 to 10, etc., the results may impact the ultimate sound quality. 
cat_doorman
It was I who was missing something. I was thinking I needed two inputs into each amp, but you are right. I guess I only need one channel on each amp if I bridge. This would also solve the impedance problem. 

I guess the next question is How does bridging affect sound quality and is it better or worse than running two stereo amps? 

Thanks Guys!
Your best option, ime and imo, and this is because you have two exact stereo amplifiers, is to passively, vertically biamp the ARs. What this entails, is each amp drives one speaker. Each amp would have one channel feeding the bass, the other channel of the same amp feeding the midrange and treble. Repeat for the other channel. One rca channel from the preamp to each amplifier, with a y splitter going to each the left and right input of the amp. All 4 speaker wires should be the same ( same for the woofers, and same for the midrange and tweeters ). Y connectors would have a 1 female rca,  accepting from the preamp cable, to a pair of male rcas, going to each channel of each amp. Enjoy ! MrD.
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
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Thanks guys. Now to find the proper splitter! It will be fun to hear what happens!