Passive preamps - differences between technologies

Passive preamps are simple but the quality of components can vary tremendously. Quality transformer based volume control (a passive preamp is basically volume control) are excellent and coveted.

a resistive ladder style can be excellent with good components.

Both are going to require a high quality multiple step selector switch.  

Avoid the sliding contact resistors as cheap and noisy.

I like passive vs active because it has the least impact on the signal (some of us call it coloration and some members here don't like that, we will agree to disagree).

Jerry

Maybe I didn't convey it correctly. I'm not saying a TVC adds warmth.

A TVC certainly can add warmth, due to ringing caused by the transformer not being properly loaded. That loading changes with each tap but the designer can't predict the load of the amplifier being used so it will only be exact at one input impedance only.

PVCs have the problem where when you turn the volume down from full up, the bass impact is often reduced. If you listen closely, you'll find that the impact it likely affected across the entire audio spectrum. The reason this happens is because the PVC is a resistance in series with the input and so the source can't control the interconnect cable (reduce its artifact) as well as it would otherwise.

You'll also find that you have to audition the interconnect cables to find one that sounds acceptable. If you've auditioned cables before and heard a difference then you know what I'm talking about.

You can see that in both cases, a buffer is handy to prevent these issues occurring. Its possible to make something too simple and PVCs and TVCs are a good example.

I've used a range of Stepped Att', with the DACT Brand being the most expensive.

A few lesser types than DACT, when used in my system put a lot of their traits into the end sonic, I recollect not much being an attraction. 

I also use the Slagle AVC and know the Promethius TVC very well.

Both are in my view, as a Standalone an improvement over a Stepped Att'.

The AVC and TVC do add a hint of Richness, but that is probably the result of the windings. The overall presentation is where the design wins favour. 

I have heard a Khozmo used as an upgrade VC and this was quite a substantial betterment. 

On the same design Pre' as the one that had the Khozmo, I have heard it with the Prom' TVC as the VC. In comparisons the Khozmo was the one with the most attraction.

I have had Bespoke Stepped Att's made for my own pre' that is close in design to the pre's being referred to, as a result of the Khozmo. 

It looks like systems are able to be quite influential on how the VC types are perceived. 

There is also the digital VC designs, such as the 'Muses' that have been very much liked in user reports. 

Audio Research is very synergistic with other Audio Research. The REF3 or LS28se are really great preamps.

I can highly recommend the Ypsilon PST 100 Mk2.  It is a passive pre-amplifier that uses transformers to attenuate the sound:  very detaIled, nuanced, with minimal coloration.  It also has an active mode, which affects the SQ.  If you read articles about the Ypsilon, it will give you an idea of how the transformers are used to transmit the signal.