A possibility I would consider, especially with regard to the hot treble, is that digital noise at RF frequencies might somehow be coupling from the DAC, or from whatever is providing the digital signal to the DAC, into the circuitry of your preamp, and causing effects at audible frequencies as a result of intermodulation or other conceivable effects.
The ultra-wide bandwidth of your preamp is what brings that kind of possibility to mind. Although a similar possibility also exists with respect to the amp.
Possible coupling paths include interconnect cables, AC power wiring, and radiation through the air.
So I would focus on the preamp as well as on the amp. And before deciding how to proceed it might be worthwhile for experimental purposes to try whatever non-Spectral preamp you can readily get your hands on (that would be compatible with the 10K input impedance of your amp), that would presumably have a much less extended bandwidth and not respond to RF noise that the Spectral may be responding to.
Good luck. Regards,
-- Al
The ultra-wide bandwidth of your preamp is what brings that kind of possibility to mind. Although a similar possibility also exists with respect to the amp.
Possible coupling paths include interconnect cables, AC power wiring, and radiation through the air.
So I would focus on the preamp as well as on the amp. And before deciding how to proceed it might be worthwhile for experimental purposes to try whatever non-Spectral preamp you can readily get your hands on (that would be compatible with the 10K input impedance of your amp), that would presumably have a much less extended bandwidth and not respond to RF noise that the Spectral may be responding to.
Good luck. Regards,
-- Al