The short answer, in my experience, is that the HT passthru will impart it's own sonic signature but it'll be more subtle than direct comparisons between the pre/proc and the preamp alone.
I did a similar comparison awhile ago. I had a B&K preamp processor and was considering buying a tubed preamp with HT passthru for 2 channel listening. The dealer let me demo it at home. My CD has dual outputs so I hooked one set to the CD input on the pre/proc and 1 to the CD input on the tubed preamp. I then switched back and forth between which units output was connected to my amp. I played a track through the pre/proc then switched cables and played the same track through the tubed preamp (making sure the volume was equal). The differences were rather dramatic.
But when I hooked up the pre/proc to the HT passthru and compared, the differences were much more subtle. The reason, I'm fairly certain, is that the signal isn't technically 'bypassed', it's rerouted within the preamp and passes through tubed stages or other circuitry that imparts the sonic signature of the unit to a somewhat lesser degree than it's other inputs (CD, Tape, etc.).
I personally like this since I like the sonic signature of the tubed preamp. But, if you use the HT passthru when comparing, it will lessen the differences between the units. Hope this helps..
I did a similar comparison awhile ago. I had a B&K preamp processor and was considering buying a tubed preamp with HT passthru for 2 channel listening. The dealer let me demo it at home. My CD has dual outputs so I hooked one set to the CD input on the pre/proc and 1 to the CD input on the tubed preamp. I then switched back and forth between which units output was connected to my amp. I played a track through the pre/proc then switched cables and played the same track through the tubed preamp (making sure the volume was equal). The differences were rather dramatic.
But when I hooked up the pre/proc to the HT passthru and compared, the differences were much more subtle. The reason, I'm fairly certain, is that the signal isn't technically 'bypassed', it's rerouted within the preamp and passes through tubed stages or other circuitry that imparts the sonic signature of the unit to a somewhat lesser degree than it's other inputs (CD, Tape, etc.).
I personally like this since I like the sonic signature of the tubed preamp. But, if you use the HT passthru when comparing, it will lessen the differences between the units. Hope this helps..