Jeff Rowlands Amp and Dac vs. VAC amp and DAC

Thanks for that input, RHL. I would point out, though, that the MC-275 in particular, and also most and perhaps nearly all ARC power amps in particular, have considerably lower output impedances (corresponding to higher damping factors) than most other high quality tube amps. And although those numbers are not specified for the various VAC models, I would feel very confident that difference would apply in their case.

And in fact the MC-275 is arguably almost in solid state territory in that respect, with a specified damping factor of "greater than 22" for the latest version, corresponding to an output impedance on the 8 ohm tap of less than 8/22 = 0.36 ohms.

Although the ARC GSi75 integrated which Pokey reported to work beautifully with the Sabrina is something of an exception in that regard, among ARC amps, having a specified damping factor of "approximately 4," which corresponds to a higher output impedance than is typical for their products. But assuming the 4 ohm tap was being used when he listened to it, I suspect the corresponding output impedance was probably still lower than on the 4 or 8 ohm taps of most or all VAC products.

On the other hand, though, there can sometimes be a tradeoff between which tap is most suitable for a particular speaker, and which tap results in the output stage of a particular amplifier seeing a load that it is happiest with (e.g., which results in the least amplifier-generated distortion, or amplifier-generated distortion that is least offensive in terms of its spectral distribution). So, yes, for that reason among others it would be advisable for Rinpoche to try all of the available taps.

Regards,
-- Al

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?

Also, from what I understand, the JR amp doesn't need anything like this, right? It just needs to be adjusted via the Aeris according to the manual.

I am happy to hear there are fans of the JR 625S2/Aeris combination. And VAC lovers as well. At least I know I am in the right zone. Thanks

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?