Certtainly nothing special about the sound. I briefly owned a Power 2 and it was on of the worst sounding amps, SS or tube, I have ever owned. Was glad to see it go.
It is well-known that SF gear used very good parts quality and build was excellent. However, I personally had some issues with their Line 1 preamp and on one occasion, with a Power 2 amplifier.
Overall though, there is much to like about SF gear, I would own it again in an instant although more recent gear sound more transparent and resolving in my opinion. I recently compared an Ayon Orion integrated to a Line 2 - Power 2 SF combo - The SF had it on power, but everything else sounded much more refined on the Orion.
For tube amps, its all about the following:
Placement of coupling caps so it doesnt become a microphone for the high currents supplying the filaments.
Careful attention to grounding and floating certain parts.
and a good startup circuit that warms up the the filament before operating B+ is fully applied.
SF power 1 and power 2 are wonderfully designed amps.
Just that voicing misses the mark with ultralinear.
Thanks for the feedback.
I will be reposting in Tech Forum.
Yesterday I spent about 4 hrs with 3 different amps, including the SF1, doing various outlet configurations.
Again SF1 was most "resistant" to any inpact from being plugged into different outlets or different conditioners, but I was also able to eliminate the problem with other amps (which I have been experiencing up to this point) by plugging it into a different outlet and also pluggin my pre-amp into yet another outlet...