Autoformer versus Transformer Passives?

Well, technically (I think) the only advantage supplied by transformers is galvanic isolation from sources passing DC to the amplifiers. But, if DC is not an issue, then the single winding of the autoformer is simpler, more direct, and ultimately "purer" than the two windings of a transformer.

In theory...

I think the isolation is the one theoretical advantage. There does seem to be less "stuff" in the autoformer which would seem to be a plus. I wonder if this bares out in listening impressions. All I know is the TAP-X sounds great, but I never was able to compare it head to head with a TVC. When I bought the TAP-X I was given the option to get it with the S&B tranformer or the Slagle autoformer and chose the latter simply on the grounds that in the passive world less should be better as long as you are addressing impedance matching effectively.

I have an S&B TX-102 TVC and it is great when in a properly matched system. Worked beautifully between my upgraded Museatex Bitstream dac(4V output) and former Art Audio PX-25 & Welborne DRD 300B SET amps. But, couldn't use it between my phono preamp and amps.

I remember when Dave Slagle first started winding(or posting about winding) his own transformers for his DIY SET amps. He and Mickey from Magnequest transformers would have long, really interesting discussions about all the factors that go into transfos on Audio Asylum. Then, he started making autoformers and I have been really intrigued ever since.

I had an S&B MKIII based passive made by K&K, but it was too long agon and the system context was different. I got the Bent based on user comments here and Teajay's review of the TAP. There seems to be the view that the Slagle autoformer sounds better the S&B transformer, but I've not seen much comment on Audiogon. If a preamp is suppose to be neutral and simply let the source to the amp with attenuation, it does seem passive setups with sufficient gain to drive the amp would function that way. I would like to see a shootout with something like the BENT-TAP-x versus some of the 10K and up active tube preamps. It does seem that a passive that can control the interconnect capacitance should be the ideal, with the amps adding whatever color or flavor the listener prefers.