Shrill high frequencies

The solution was to plug the Isotek into an Audioquest Power line 2 with a Nordost QRT inserted.

Thanks to all for sharing your mighty brains and happy listening! 

Did you try the Isotek PC that came with the unit?  I too have a Sigmas and have noticed no brightness at all.  I use a Synchro with it, but a regular PC would be fine.

Try MIT or Transparent cables and IC's instead of the Cardas/Nordost Frey. That should do it.

Matt

I have the Isotek sigmas unit.  I did a power cable shoot out with my amp, and found that Shunyata cables did not like being plugged into the Isotek.  Especially the NR versions.  Although I did not have issues with high frequencies, in my case it was a tonality issue.  I plugged the amp directly into the wall.  Even with other PCs, I recommend trying plugging the amp into the wall.  

Maybe the Isotek needs more break-in time. 

BTW - I use a MD 108T + KEF LS50 and those 2 are definitely not bright. My Accuphase T-101 tuner is much brighter than the MD 108T

At your suggestion I changed the power cord from that provided to Shunyata Delta. No joy. Maybe break-in time will help. 

Magnum Dynalab MD 108 tuner, Modwright modified Sony HAP Z1ES, Audible Illusions Modulus 3A with all factory upgrades, either an Atma-Sphere S-30 mk 3.3 or Luxman MQ-88UC amp KEF LS 50 speakers 2 REL Stentor subs. ICs are all Cardas Clear, speaker cables Nordost Frey 2, power cords Shunyata. 

Amp is Luxman MQ-88UC, preamp Audible Illusions Modulus 3b factory upgraded, sources Modwright modified Sony HAP Z1ES,.Magnum Dynalab MB 108 tuner. All IC cables are Cardas Clear , Speaker cables Nordost Frey 2. Speakers are KEF LS 50 or Goldenear Triton 1, subs REL Stentors. 

+1 lalitk

Did you allow enough ‘break-in’ hours? Also, experiment with PC feeding the IsoTek. 

Tell us about the rest of your system.