Well put questions. My intuition as an EE is that the improvements you noted revolve around the fact that you are using a very early preamp and amp (even if they have been modified/upgraded). I suspect your findings would be different with newer electronics.
I would think that although energy stored in the inductance of the transformer may be a factor, it is more likely that the transformer's most significant effects are due to filtering of high frequency hash that may be on the ac line (the filtering being provided by its limited bandwidth), and also to the ground isolation that it provides.
I suspect that your preamp and amp have less than ideal isolation between their chassis (which are probably used for signal ground) and ac neutral, due to component degradation that has occurred over time. That would have sonic effects that are hard to predict in both character and magnitude, but would almost certainly be negative. Likewise for the effects of incoming hash/noise/rfi on the ac line. The transformer very conceivably would help in both areas, but would have different and probably lesser effects with modern gear, due to the modern gear probably having components which are in better condition, as well as perhaps better overall power supply design, and components such as capacitors which are better quality to begin with.
I'm not experienced with plc's, but I've seen a lot of comments here from experienced people that with modern, quality, gear they usually do more harm than good. Not sure why that would be so. Most of them, I'd imagine, provide inductive and capacitive filtering of high frequency garbage, as well as isolation.
There are one or two very expensive models that actually convert the incoming ac to dc, then use the dc to power an ac oscillator and amplifier, thereby providing a really pure ac source. I have not seen any assessments of those units.
Regards,
-- Al
I would think that although energy stored in the inductance of the transformer may be a factor, it is more likely that the transformer's most significant effects are due to filtering of high frequency hash that may be on the ac line (the filtering being provided by its limited bandwidth), and also to the ground isolation that it provides.
I suspect that your preamp and amp have less than ideal isolation between their chassis (which are probably used for signal ground) and ac neutral, due to component degradation that has occurred over time. That would have sonic effects that are hard to predict in both character and magnitude, but would almost certainly be negative. Likewise for the effects of incoming hash/noise/rfi on the ac line. The transformer very conceivably would help in both areas, but would have different and probably lesser effects with modern gear, due to the modern gear probably having components which are in better condition, as well as perhaps better overall power supply design, and components such as capacitors which are better quality to begin with.
I'm not experienced with plc's, but I've seen a lot of comments here from experienced people that with modern, quality, gear they usually do more harm than good. Not sure why that would be so. Most of them, I'd imagine, provide inductive and capacitive filtering of high frequency garbage, as well as isolation.
There are one or two very expensive models that actually convert the incoming ac to dc, then use the dc to power an ac oscillator and amplifier, thereby providing a really pure ac source. I have not seen any assessments of those units.
Regards,
-- Al