Don't think my preamp likes feeding signal to two seperate places.

Fundsgon,

with the SMS-1, I just st wedge another set of speaker cables  at  the amp terminals? You sure there are no ill effects from doing that?

I see. Yep, an impedance doulber or quadrupler would do it for you. :)

Regarding the SMS-1, the one concern I would have about connecting it to the DS450 outputs relates to the fact that the DS450 is a differentially balanced amp. So presumably its negative output terminals as well as its positive output terminals have full amplitude signals on them. The concern would be that depending on the internal grounding configuration of the SMS-1 and the design of the external 12VDC power supply it apparently uses, that a low impedance path might be created from the amp’s negative output terminals to the circuit ground of the SMS-1, then through some unknown but possibly low impedance to the AC safety ground of the SMS-1’s power supply, then via the AC wiring to the amp’s AC safety ground, then probably through a low value resistor within the amp to it’s circuit ground. In effect possibly putting a near short circuit on the amp’s negative output terminals, and applying a much higher voltage across that resistor than it was designed to handle.

If the SMS-1’s power supply had a two-prong AC plug (i.e., a plug that doesn’t have a safety ground connection) I would be confident that wouldn’t be an issue, but photos I found online appear to indicate that it has a three-prong power plug, which leaves me uncertain.

So if you decide to go that way it I’d suggest asking Velodyne what the impedance is between the SMS-1’s negative speaker-level input terminals and the AC safety ground pin of its power supply. If it is high, or if those points are electrically isolated from each other, there won’t be a problem.

Regards,
-- Al

So many considerations just to add a subwoofer without comprimising my signal for the main amp!!! Sheesh!

 almarg, thanks for your insights.  Another idea- what if I used balanced to SE converters and used the other currently unused  balanced output on the preamp. Would that put me where I need to be to not have the low pass phenomenon, or would this be a continuing problem. Not keen with the math formulas. I appreciate your help. 

P.S. to my previous post: Now that I think of it, even if the SMS-1 wouldn’t create the problematic circuit path I described above, a similar path might be created via the SMS-1’s connections to the Adcom amp, and then via the Adcom amp’s safety ground connection (assuming it has a three prong power plug). Sheesh indeed :-)

what if I used balanced to SE converters and used the other currently unused balanced output on the preamp.

That should work ok provided that the chosen converter has a relatively high input impedance, so that the parallel combination of that impedance and the input impedance of the DS450 is not too low for the preamp to handle comfortably. (Keep in mind that the preamp’s two XLR output connectors for each channel are undoubtedly wired directly together, and driven by the same output stage).

It’s never been clear to me if ARC’s 20K minimum load recommendation applies to the balanced outputs or the unbalanced outputs or both. But to be safe in this case I think it would be preferable to look for a converter having an input impedance of 47K or more.

Good luck. Regards,
-- Al