2. amps-preamps
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Mixing XLR and RCA outputs when biamping?

I’m about to introduce two new (to me) amps into my 2-channel system, and wondered about how to hook them up.

 

The amps are refurbished Adcom GFA555s1, and I plan to bi-wire them vertically.  My preamp (NAD C658) has both XLR and RCA outputs,  and it appears they output simultaneously.    However, the amps are RCA input only (no XLR input).          It would seem I have a couple of options:

 

1. use the RCA output of the preamp, and split each signal to feed both channels of each amp.    
 

2. Use both XLR and RCA outputs, with the two left channels going to the left speaker amp.

 

Would the voltage/sound level be the same for situation 2?    I was thinking running the left XLR into the low freq on the left speaker, and the right XLR not the low freq of the right speaker.

 

this is probably a dumb idea and I should split the RCA signal.

 

 

 

 

chessie
erik_squires
16,442 posts
 

Yep,  a Y splitter is simple.

The issue with passive bi-amping (without a crossover) is that both amp channels still provide the same voltage swing, but with twice the power supply you used to have.

With a miniDSP you can do a couple of more advanced things:

  • Reduce the load on the mid/treble amplifier
  • Reduce the load on the woofer amp
  • Fine tune the bass to your room with DSP
  • Improve efficiency by removing level adjusting resistors since you can use miniDSP to set the relative mid/treble to woofer levels.

I think the Y splitter is the best place to start, and maybe look into getting into active a little bit at a time.  For instance, you could use the miniDSP strictly as an EQ and Y splitter first.  When you get more comfortable you can consider bypassing the woofer crossover. :)

 

barts's avatar
barts
736 posts
 

Using a Y will necessitate that you bi-wire (which for most systems is a waste of time and money in my opinion).

Considering that the amps are just refurbished I personally think your best bet is to bridge both of them.  Gives you plenty of headroom and your using the speakers as intended.  To any naysayers...if the amps are virtually as new or better and were designed to be bridged in the first place just go for it.

I ran ARC bridged amps for many years with no issues. 

Regards,

barts

  

chessie OP
25 posts
 

Thanks Barts.    Not sure why Y splitter necessitates bi-wire?   Can you explain?

Bi-wire to me is taking one output channel off of the amp and splitting it into two wires for the speaker inputs.   I agree, this doesn't make much sense as to why it would be beneficial.

What we are talking about is Y-splitting the output from the pre-amp so it can feed both channels of the amp with the same signal.   At that point you have of the two channels to feed each speaker (vertical bi-amping, not bi-wiring).    

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