Autoformer versus Transformer Passives?

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.

Your (previously my) K&K used S&B MkI transformers, not MkIII. The difference was the MkI version tended to sound a little warmer.

Hi Anthony. I stand corrected. Have you heard any of the Slagle transformers stuff?

Working on getting the new Slagleman's. These are sold by Intact Audio. Sort of a "nude" version of a non-remote TAP-X. I'd like to compare them to my Lightspeed and hopefully can remember enough about the S&B MkI's to make a reasonable comparison. I'll let you know the results when I get them and have had enough time to listen.

I have spoken with Dave several times and made a few autoformer preamps for friends, using his and Pieter's autoformers.
Transformer passives have more bass distortion as compared to autoformers. This is easy to confirm: look up the low frequency response graphs at S&B and Sowther sites, also, Jensen line input transformer data sheets, including % of harmonic distortion at low frequencies. A magnetic core will saturate and distort with a combination of very low frequencies AND high input signal levels.
OTOH, a transformer's galvanic isolation is great to get rid of ground hum issues, it also attenuates very high-frequency digital noise such as the normally unfiltered SACD outputs or out-of-band DAC artifacts.
IME, autoformers have great bass, outstanding headroom and can be made to roll-off smoothly at ultrasonic frequencies.
In summary, IMO, if your system has ground-induced hum, or an SACD player or your CD player outputs digital HF nasties, use a transformer volume control.
IMHO, if your sources are clean of HF noise and there is no ground-induced hum, an autoformer is a superior solution across the board: bass, dynamics, low level detail, frequency response, distortion AND musicality.
My 1c worth (adjusted for recession)