Jeff Rowlands Amp and Dac vs. VAC amp and DAC

ARC, Mac and Airtight will all work with Sabrinas and they will all sound completely different. The Mac--warm, rounded, rich but slightly veiled in comparison to ARC which will be more transparent, open and expansive, but not strident. I have owned both with Wilsons and these are my conclusions. Airtight is an excellent company whose amps I have enjoyed listening to but never with Wilsons. Good luck.

Based on what Al has written it seems that the ARC  tube amplifiers may utilize a larger degree of negative feedback  (NFB) than the VAC amplifiers.  I say this due to the lower output impedance  (higher damping factor ) of the ARCs. Depending on the particular speakers this can be advantageous.  It truly is dependent on the speaker design and intent of the builder. The Sabrinas could require amplifiers with more NFB with the resultant lower output impedance. Again,  nothing substitutes for actual listening experiences. 
Charles, 

I concur with GPGR4Blu... "ARC which will be more transparent, open and expansive, but not strident."

In my experience at RMAF for several years, ARC amps have been consistently my favorite amps, together with Rowland and Solution. They all meet my sound/musical concept.

Unfortunately, high power tubed amps like ARC require upkeep to maintain top notch performance -- tubes sag over time. I personally prefer to have "launch & forget" devices in my home.

G.

Charles1dad 5-25-2016
Based on what Al has written it seems that the ARC tube amplifiers may utilize a larger degree of negative feedback (NFB) than the VAC amplifiers. I say this due to the lower output impedance (higher damping factor ) of the ARCs. Depending on the particular speakers this can be advantageous. It truly is dependent on the speaker design and intent of the builder. The Sabrinas could require amplifiers with more NFB with the resultant lower output impedance. Again, nothing substitutes for actual listening experiences.

Yes, that’s all true and well said, Charles. The VAC 200iq is specified as using 6 db of feedback, while the ARC Ref 150SE, for example, is specified as using 14 db, a considerable difference. I’ve never seen the corresponding number for the MC-275, but its unusually high damping factor (for a tube amp), its somewhat low gain (feedback reduces gain, everything else being equal), and numbers I’ve seen for other classic MC tube amps, suggest to me that it could be in the vicinity of 20 db or so.

My older VAC Renaissance 70/70 MkIII amplifier, btw, has a six-position switch that allows the user to select the amount of feedback. The settings range from zero to 7.5 db. I use the zero feedback position, which works well with my particular speakers (which have a particularly flat impedance curve and no dips to low values at any frequency).

As you indicated, judicious use of feedback in a design can be either advantageous or disadvantageous depending on the characteristics of the speaker that is being driven. And also on how well the design of the particular amp avoids the sonic downsides that feedback can potentially introduce.

Best regards,
-- Al

So far, it sounds like JR is still winning for combining great sound and ease of use. And perhaps the VAC 200iq is next given its new self-biasing feature, though I have still to hear it. The exciting listening adventure continues!!