Thanks for the mention, @david_ten , and for your good catch on those specs.
I agree with the comment by gs5556, and in fact I was suspicious of that 70 watt number as soon as I saw it. Class A amplifiers typically do not provide dynamic headroom anywhere close to a near doubling of output power relative to their continuous power rating. In fact they commonly provide essentially no dynamic headroom.
So consistent with gs5556’s comment the 70 watt number is presumably the product (multiplication) of peak voltage and peak current, rather than the product of rms voltage and rms current which is how continuous power ratings (37 watts in this case) are specified.
But, hypothetically speaking, if the amp were in fact able to put out 70 watts defined in the same manner as continuous power ratings are defined, since for a given load impedance power is proportional to the square of voltage, if 1.5 Vrms produces 37 watts the input voltage required to produce those 70 watts would be 1.5 x (square root (70/37) = 2.06 Vrms. Still low enough to be generated by most DACs.
On the other hand, though, those sensitivity numbers presumably apply when the amp’s volume control is at max, and the OP may be looking for a DAC providing greater than usual output voltage to lower the settings of the volume control that he uses. Although he should keep in mind that as has been said in a number of past threads here higher volume control settings (even close to max) more often than not tend to be sonically preferable to lower settings, if it makes any difference at all.
Best regards,
-- Al
