speaker cables

[Scottmoose]

Hmm. FWIW (not much) the sharpness noted at the top end could be due to the relatively high capacitance of the Cat5 / 6 / whatever. High capacitance wire can cause oscilation in some amps, which results in almost identical traits to those you describe Steve -a sharpening / roughening of the top end in particular. Only a guess though. I don't pretend to be up on amplifiers.