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Ref 3 Impedence Mismatch HELP please

I've recently discovered I have an impedence mismatch between my Xilica XD 4080 digital crossover and the ARC REF 3. The input impedence on the Xilica is 10K. Which is too low for the REF 3. This causes issues with the sound in the high frequencies and lows. It seems like a Burson Audio XLR Audio Buffer would be the solution but apparently they are not importing them into the country any more.
I was wondering if there is another product or manufacturer that might have a product as a solution or if there is any way to raise the input impedence of the Xilica Crossover by adding caps or resistors as in internal mod.

Any ideas? I know I can always replace the preamp with a solid state unit which I'm contemplating.

As an after thought, wouldn't it be great if the audio manufacturers could at least codify the specs for all audio equipment so that these problems could be prevented? All manufacturs would have to at least hit a target input and output impedence so that all equipment could work together electrically. It seems a no brainer for the industry to develop.
sgr
herman
2,277 posts
 
.

the output impedance of the ARC goes higher as the frequency goes lower.

Good point, any idea how much that would be? I have no idea what size caps they use.

There is no good way to fix this- either

Bigger caps? I realize that most would be reluctant to do surgery on such an expensive pre but if not then why not just up the value?

.
almarg's avatar
almarg
9,670 posts
 
Any idea how much that would be?
http://www.stereophile.com/content/audio-research-reference-3-line-preamplifier-measurements:
The output impedance was also to spec., at 635 ohms balanced and 326 ohms unbalanced in the treble and midrange, but rose to 1437 ohms and 625 ohms, respectively, at 20Hz.
The OP's processor has only balanced inputs. A rise in preamp output impedance from 635 ohms in the mids and treble to 1437 ohms at 20Hz is non-ideal in relation to a 10K load (assuming that spec is accurate), but on the other hand doesn't seem likely to cause more than a very slight bottom octave rolloff.

Not sure why there would be issues with the highs, as the OP reported, unless the interconnect cables are particularly long and do not have low capacitance per unit length. In that situation, perceptible upper treble rolloff could result from the interaction of cable capacitance and preamp output impedance.

Best regards,
-- Al
bifwynne
2,206 posts
 
Sgr, pull my old OPs that considered a very similar problem, in some ways even worse than what you have. I used to own a Ref 3 and now a Ref 5. A fellow by the name of Tom Tutay built a custom impedance buffer for me.

Admittedly, it is principally for the Ref 3/5's Main #2 output that powers my sub, not my main outputs. I would call Tom and see if he can custom build something for you. My only concern is that inserting an artifact into your main signal path may cause a different set of problems. But do give Tom a call. He is top drawer. His number is listed on my OPs.
atmasphere's avatar
atmasphere
12,088 posts
 
Herman, Bifwynne's suggestion is a good one- Tom is a good guy and knows his stuff.

If you install larger coupling caps, the caps themselves will color the sound to a greater degree.

The bottom line here though will be that if you use this preamp with this crossover, you are likely to wind up with some sort of coloration or artifact- this is a tricky problem to get around.
vladimir
346 posts
 
A buffer changes the entire picture. If you want a ARC Reference preamp doing its thing, get an amplifier with an input impedance of 50kOhms or higher.
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