Jeff Rowlands Amp and Dac vs. VAC amp and DAC

Rinpoche,
The "taps" are what you connect the speaker cables to on the rear of the amplifier. They are clearly labeled as 2 ohms,4 ohms, 8 ohms etc.  The taps are in plain view. You'll have to listen to the different amplifier tap settings and just choose the one that sounds best to you. I'm glad you are enjoying this experience. 
Charles, 

You are correct. there are no speakers impedance adjustments in the Rowland M625 S2... Its output taps are expected to work for all common speaker varieties.

If you connect Aeris to M625 S2 directly, use the Aeris remote for setting volume at your preferred level. If there is a linestage between Aeris and M625, Set Aeris gain to unity/unattenuated... Solid right volume LED lit up, and then use the linestage to set listening level.

Bear in mind that results have a lot to do with the degree of break in of the devices you are testing.

Regards, G.

For now the 625 S2 would be connected directly to the Aeris. Same with the VAC. However, and I do hesitate to throw some other amps into the discussion, but what do you feel about Dan A'gostino The Classic Amp? Is that a crazy alternative? Too much for the little Sabrinas? 

Rinpoche 5-24-2016 5:18pm EDT
The tap discussion is way above my head but I am writing it down and when I go to the shop to hear the VAC 200 iq system I will ask about it. If the VAC 200 iq is one of the winners, and I get to bring it home to try with the Wilson’s -- I will report back on the combo for sure. But, if I hear you both correctly, the 8 tap is possibly the one to try first? Then the 4?

Absolutely not, in my opinion. And my apologies for wording my previous post more technically than I should have.

I don’t doubt that the 8 ohm tap may very well be the best tap to use with the Sabrina when it is driven by a Macintosh MC-275 tube amp or by most Audio Research tube amps, as was stated by an exceptionally credible and knowledgeable source (Peter McGrath). However my basic point was that the MC-275 (and other McIntosh tube amps), as well as most ARC tube amps, are COMPLETELY different animals than both VAC amps and the majority of other high quality tube amps, especially in regard to major differences in their output impedances. Which in turn are especially relevant to tap selection. Differences in amplifier output impedance mean differences in the tonal effects that result from the interaction of amplifier output impedance with the variations of speaker impedance over the frequency range.

Given all that has been said, I agree with the others that all taps on the 200iq should be tried, but my guess is that the 1 to 2 ohm tap has the best chance of being optimal, the 2 to 4 ohm tap has the next best chance of being optimal, and the 4 to 8 ohm tap has the least chance of being optimal. Among those three taps on the 200iq, by the way, the 1 to 2 ohm tap will come closest to the behavior of a solid state amp (such as the Rowland) insofar as the tonal effects of the interaction of its output impedance with the impedance characteristics of the speaker are concerned. Although of course there will still be differences between the Rowland and the VAC, resulting from both impedance interactions and the intrinsic sonic characters of the two amps.

On the two higher impedance taps of the VAC, look particularly for signs of excessive brightness, and/or for weakness in certain parts of the lower bass region, and/or for poorly defined bass.

Best of luck, and best regards,
-- Al