2. tech-talk
  3. 1216356988

Passive Biamping?

Biamping virgin, never tried it before. Speakers are bi/tri-wire capable, no outboard crossover needed or wanted.

Have four channels of power amplification (pair of monoblocks plus stereo amp, all from same maker and of similar power, if perhaps not exact identical gain), of fully-balanced/bridged design, utilizing balanced input transformers with XLR and RCA inputs.

Preamp is fully-balanced, but has (like many such beasts that provide RCA inputs in addition to balanced XLR inputs) one pair of XLR main outputs and one pair of RCA main outputs.

If the preamp had two pairs of XLR outputs, this would seem easy. Likewise if the amps had daisy-chain line outputs. But alas, like most, they don't. Yet I would like to A) keep the signal fully-balanced all around, and B) not incur the 6dB gain difference that would result from taking both the balanced and single-ended feeds from the preamp. (I've inquired with the preamp maker; unfortunately the RCA outputs cannot be converted to a second set of balanced.)

The preamp (like the amps) is solid-state, and doesn't lack for sufficient output drive/low output impedance, but the input-tranny configuration of the power amps does mean they have a somewhat lowish input impedance at 10K-Ohms, should that imply anything for splitting the feed.

So what is the best path to biamping success here? (No, replacing the preamp is not a good option.) It seems to me this general situation -- biwire speakers and four channels of suitable power amplification all on hand, but preamp lacking two pairs of identical main outputs -- couldn't be all that uncommon, but I've never seen XLR Y-interconnects for sale, if that's what's needed...
zaikesman

Showing 1 response by dotsystem

dotsystem
81 posts
 
You may need attentuators on one of the amps. Far less than a 1 db imbalance can be enough to skew the tonal response. You could use a single amp with jumpers on the speakers as a reference point for the "normal" tonal balance. On some speakers, the gauge of the jumpers relative to the main speaker cable may also effect the tonal balance.

If there is an amp level mismatch, you also might experiment with the mixed preamp outputs. Connect the XLRs to the amp with less gain.

With attentuators, you can dial it in. Depending on the crossover frequency, attentuators on the bass amp might not effect the perceived signal purity too much. On the treble amp, YMMV.

Even when the tonal balance is correct, a big disparity in dynamic range or slew rate between the amps may make for a disjointed sound. Again, using a single amp with jumpers will provide a point of reference.
More to discover