Hi Charles,
Yes, it is puzzling how a component could be spec’d so inaccurately, especially one that is so highly regarded and was designed and originally spec’d while the company’s very highly regarded former designer was still there. Those original specs, BTW, included the same 400 ohm output impedance number that is still published, as you correctly indicated.
One point I would add for the OP is that if he does go with the SLP-05 the high output impedance at all frequencies will tend to magnify certain interconnect cable effects. So it would be preferable to avoid particularly long lengths of interconnect cabling between it and the power amp, especially if the particular cables do not have low capacitance per unit length. The interaction of the high output impedance at high frequencies with high cable capacitance would tend to introduce at least a slight amount of rolloff and/or undesirable phase shifts in the upper treble region. And that would apply regardless of whether balanced or unbalanced interconnections are used, since the two output impedances were described by JA as being similar. Something like 15 feet of cable having 35 pf/foot capacitance (525 pf total capacitance) should be ok though, at least as far as that effect is concerned.
Best regards,
-- Al
