Do all Passive preamps exhibit this trait

Contrary to Clio's advice, if you want to get the most out of a passive your best bet is to match the amp and source for input and output. IOW, the source output should be just barely able to drive the amp to full output.

This will mean that the passive is turned up all the way for full volume. The advantage of this is that passive controls traditionally limit dynamic contrasts and bass impact as you turn the volume down, due to the interaction between the cable, the input of the amp, and the control itself. So to minimize this you will want to set things up so that you are operating the passive at or near full volume.

A properly designed active line stage will be able to control the interconnect cable to a great degree, in fact that is one of the functions of the line section. If done right, the cable will cease to have any serious consequence regardless of its length or construction, but too many active line sections are designed without this in mind, hence a passive can give them a good run for the money. But if the active line stage is designed and built right, no passive made will challenge it.

Ralph,

That was not my experience using the S&B transformers. My setting was about 12 o'clock and it was fine in my system. My amp was .8V sensitivity with high gain and 67k input impedance.

I do agree in principle with what you are saying and the data in the S&B link I provided bears this out. However, it appears that the data also supports that the changes in impedance due to the volume control setting are not that big a deal and I would have to agree based on my experience.

Hi Clio09, with TVCs its a different game and in that context I agree with you. My comments apply only to passive volume controls that are transformerless.

A properly designed TVC can, IMO, do better than the best PVCs; in fact I think that unless you have the very best in an active line stage, that a good TVC is going to be one of the better if not best alternatives.

Lack of dynamics hasn't been my experience with any of the passives I've owned:

Promitheus TVC
Sonic Euphoria (autoformers)
Bent TVC (S&B trannies)

In all of these cases, dynamics seemed explosive, not lethargic. The presentation also seemed airier and more detailed than actives in the same price range. I've heard the new Bent passive with Dave Slagle's autoformers and would say the same thing.

I don't doubt the calculations show:

passive controls traditionally limit dynamic contrasts and bass impact as you turn the volume down, due to the interaction between the cable, the input of the amp, and the control itself

but in practice, these shortcomings were minimal or inaudible in my system. This was especially true of the Sonic Euphoria and Bent with autoformers. Low level listening with these passives was a pleasure. They had a fullness at low volumes that seemed more natural and proportional than an active.

However, a back-to-back comparison of the Bent TVC and an Audible Mod3a indicated something was missing in the midbass area. A friend and I both agreed that the Mod3a was noticeably warmer in a good way. After a year of intense interest in passives, I've returned to an active, but I still believe a good autoformer-based passive will outperform most actives in the sub 1000 category.

Ralph, glad we're on the same page with TVCs, although I trust your passive volume control option for the M-60s is well designed.

Mingles, my K&K TVC (S&Bs) outperformed my Cary SLP-98 ($3995) and Joule Electra LA-100 MkIII ($3750). I'd venture to say the Bent units in particular, either the S&B or Slagle models will outperform many preamps, both sub and over $1000.

Now Dave Slagle has come out with a manual DIY version using boards developed by John Chapman for a ridiculously low price. Just add a case and some RCAs and you're done. Even if you had someone build it for you it would still be a bargain.

See here:

http://www.audiogon.com/cgi-bin/cls.pl?preatran&1230319450&/Intact-Audio-Slagleformer-Modu