In regards to using the separate 12V secondary windings to give each channel it's own heater supply, how concerned should I be about this warning on the Triad datasheet:
Primary and secondary windings are designed to be connected in series or parallel. Windings are not intended to be used independently.
Is this warning meant for the primaries only?
Primary and secondary windings are designed to be connected in series or parallel. Windings are not intended to be used independently.
Is this warning meant for the primaries only?
It says "Primary and secondary" in what you quoted... My guess is that if the current drawn is the same on both windings, they can be used independently. I can't see a reason not to parallel them though. Or, if you want, you could connect them series and use "full wave" rectification instead of a bridge.
I'm pretty sure the warning is just to ensure that the secondaries aren't left floating with regards to eachother, as they would in some cases develop a pretty large voltage between them. If both are referenced to ground, or some other common voltage you should be fine. When I use Antek toroids I routinely use one heater winding per channel, and then tie both windings to a common ground or heater lift reference. it ends up symmetrical and easy to route, as well as troubleshoot later on.
So the Triad VPT24-1040 takes care of my 12VDC heaters for the phono stage. Nice.
Could I do something similar for my AC-heated line stage (separate heater supplies per channel)? I'm currently running AC heaters off a 6.3V CT secondary winding of the main PT, and I want to stay with AC. Can I use something like the Triad VPT12-2080 and use the dual 6V secondaries for the two channels, creating an artificial center tap via resistors for ground reference for each secondary winding? This would also serve the purpose of ensuring all heater supplies are separated from the main PT which provides B+.
Could I do something similar for my AC-heated line stage (separate heater supplies per channel)? I'm currently running AC heaters off a 6.3V CT secondary winding of the main PT, and I want to stay with AC. Can I use something like the Triad VPT12-2080 and use the dual 6V secondaries for the two channels, creating an artificial center tap via resistors for ground reference for each secondary winding? This would also serve the purpose of ensuring all heater supplies are separated from the main PT which provides B+.
Sure, that would work fine. I do the same thing off of my single transformers, and I pretty much use AC heaters exclusively in my builds. I like to put the heater wiring to the highest-current demand sockets first, and then daisy chain additional twisted pairs to any additional sockets from there, usually ending at the input tube socket. Here I run a pair of 100R resistors as an artificial center tap, and then ground the junction, or run a wire to a heater lift from there. Dead quiet if tightly twisted and routed correctly away from other sensitive bits. Do this with one wireset per channel from the transformer. Easy peasy 
I've only had to resort to DC a couple times these last few years, and I suspect even then that it was due to noisy power coming from the mains. I only run DC if it shows absolutely necessary, or if it's just plain easier (single tube builds with on-hand or junkbox transformers, etc) when I can help it.
I've only had to resort to DC a couple times these last few years, and I suspect even then that it was due to noisy power coming from the mains. I only run DC if it shows absolutely necessary, or if it's just plain easier (single tube builds with on-hand or junkbox transformers, etc) when I can help it.
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