Anwar 4-24-2016The measurements section of Stereophile’s review of the Ref 5 SE states as follows:
The AR REF 5SE needs a high impedance power amp, 100k or higher.
At high and middle frequencies the Ref 5’s output impedance was slightly higher than specified, at 628 rather than 600 ohms balanced and 322 rather than 300 ohms unbalanced. However, at 20Hz the impedance rose to 1447 ohms balanced and 637 ohms unbalanced, which, with an extremely low load impedance of 600 ohms, rolls off the low bass by 3dB at 15Hz (fig.1, cyan and magenta traces). Into the more realistically high 100k ohm load, however, the Ref 5’s low-frequency response is flat to below 10Hz (fig.1, blue and red traces).This does not by any means suggest that a load impedance of 100K or more is necessary. Nor does this:
Anwar 4-24-2016Obviously, there are a great many differences in design between ARC power amps and an MC452 besides their input impedances.
I have tried my Ref 5SE with various amps, including direct connection to my MC452 which is 22k. From my own experience, it sounds the best with AR power amps and their input impedance is indeed very high.
The measured maximum output impedances of 637 ohms unbalanced and 1447 ohms balanced (which means approximately 723.5 ohms for each of the two signals in the balanced signal pair) seem suitable for driving a 20K load, based on the 10x rule of thumb guideline (as applied to the highest output impedance at any audible frequency). But even if that were to be a bit marginal in some systems, 47K or thereabouts would certainly seem very comfortable.
Driving a lower impedance load will not damage the Ref5 SE, it will only lower its sound quality."Driving a lower impedance" than what?
Regards,
-- Al