2 REL Strata Subs and Mono amps

Thanks, Hifigeek. Jdolgin, descriptions I found of the VM220 indicate pretty clearly that it is fully balanced. However, as Hifigeek's comments make clear, the fact that it is a tube amplifier having an output transformer introduces still more variables and unknowns into the already "confusing mess" which you aptly described.

I've seen some older ARC schematics, such as this one for the fully balanced VT130, showing circuit ground as being connected to the 4 ohm output tap of the amp, rather than the common (black) terminal, and with circuit ground and chassis ground being connected to each other through a 10 ohm resistor.

*If* Hifigeek determines that the design of the VM220 is similar in those respects, I think that you could connect the black wire to the 4 ohm output terminal of the amp, and the red and yellow wires to the 8 ohm terminal.

Alternatively, assuming that is how the design is implemented, you could connect the black wire to the 4 ohm output terminal, and the red and yellow wires to the common (negative) terminal. Doing that would introduce a 180 degree phase reversal between the sound produced by the sub and by the main speakers, which you would correct for with the sub's phase reversal switch, assuming it provides one. Doing it that way would result in the sub receiving a somewhat (about 8 db) greater signal level than if you were to connect between the 4 and 8 ohm terminals.

But we'll see what Hifigeek determines.

Regards,
-- Al

Amazing....how complex the solution can be for a seemingly simple question.
Oh well, I guess in the hiigh end game NOTHING is ever simple.
Thanks everyone.
jdolgin

Zormi, I normally don't suggest components unless the poster asks or presents alternatives himself. In your case, I would suggest giving a good listening to the Confidence C1 IIs at about half the Diablo's price. In my humble opinion they are among the best standmounts ever, for several reasons: deep and controlled bass enough even for medium-sized rooms, a soundstage that includes height reproduction, something rare among non-tower speakers (even Vandersteen 5s and 7s, as well as highly rated standmounts such as Raidhos don't do it), and all around sound as good as anything at two or three times the price. The C1 IIs definitely don't need a crossover, just augment their already impressive bass with your RELs at about 30Hz or a bit below.

By the way, I checked the Gibraltar manual online and on page 12 it explains the way to connect to differential amplifiers such as your Krells, basically to connect the black Speakon wire to a chassis screw as was explained by others here. That's also how Nelson Pass suggest doing it with his balanced amplifiers, and he provides another set of ground posts just for that.

12-30-12: Vladimir
I checked the Gibraltar manual online and on page 12 it explains the way to connect to differential amplifiers such as your Krells, basically to connect the black Speakon wire to a chassis screw as was explained by others here.

Thanks, Vladimir. However, as I indicated in my first post dated today, based on my research it appears that these particular Krell amps are not differential or balanced or bridged. I suggested confirming that with Krell, though.

Regards,
-- Al

Wow Vladimir..

Nice idea with C1 MkII, already under consideration. I know them well, since I use to own original edition Confidence C1... In fact, I owned both Utopia Micro Be and Confidence C1 until the end of 2008, simultaneously. Two different worlds, each one impressive on his own way... I now prefer a bit the Utopia Diablo because a slight edge over Dyn C1 in mid/high clarity and detail rendition. Bass aside, this is where C1 excells, but RELs defeat that area as a serious issue. Price wise, I have a great dealer from Belgrade, Serbia, which is able to bring me a pair of Diablos including dedicated stands for the same money as pair of C1 MkII without stands at another dealer. But, price doesn't matter too much... differences between the two simply not prominent enough to have any serious impact on decision.