Its always between 9.30 and 9.35pm, ive had friends around and not mentioned it to them, and when it happens and the sound changes they have all asked whats happened. so i think i can rule out perception, room temp is also constant within a few degrees. Ive been busy this week but will be taking the isoket out of the system on saturday and giving it another go, and report back on whats happened.
thanks for all the comments and suggestions.
CD:- Bel Canto CD2 Player & VBL1 PSU
DAC:- Bel Canto DAC 2.5
Amplification:- Herron Audio M1A Monoblocks
Loudspeakers:- Audio Physic Sitara
Cables:- Coherent Cables - 4D Analogue, 4D Digital, 4D speaker cables.
Other Items:- Isotek GII Mini Sub mains conditioner, Power Cables :- Missing Link Cryo Reference & PS Audio AC-5, Optimum Equipment Stand