Why does my system now have shrill top end.

Kosst, I assume that I was not included among those to whom your last comment was addressed, even though it mentioned cables.  But to further clarify my comment about the OCOS cable (and Peter, thanks for the second): As you may be aware there are a few speaker cables which have ultra-high capacitance, such as Goertz and the old Polk Cobra cables. When used without a Zobel network, and especially when used with solid state amplifiers, those have been known to cause ringing and/or oscillations, and in some cases oscillations which have even resulted in severe damage to the amplifier.

After doing some research I have not been able to find an indication of the capacitance per unit length of OCOS, but it is an unconventional coaxial design having an extremely low "characteristic impedance" of about 8 ohms. That suggests a strong possibility that its capacitance is very high.

On the other hand, I would expect that the not especially extended 100 kHz bandwidth of the amp, and the relatively modest amount of feedback I believe it uses, lessen its susceptibility to that kind of effect. But it should be easy enough to rule this possibility in or out, perhaps even by using Home Depot or Radio Shack wire for purposes of the experiment, if the OP doesn’t have any other cables of suitable length on hand.

Your suggestions about the amp are of course also good ones, IMO.

Regards,
-- Al

Moderators please remove all the insulting posts, perhaps kosst_amojan himself, from this site. He continuously insults and brings down the enjoyment and civility of this once fine audiogon community. This cannot continue without many of the long time and civil members opting out of these forums.