Transformer based passives vs passive stepladder

I don't know if what I am about to say will answer your question or help you, but I am in the same boat you are right now. I am looking at and trying out a lot of passive devices. I have looked at the following so far:

Luminous
Goldpoint
Welborne Labs
EVS
Endler

Most of the above are resistor based with the last two being nude attenuators that you plug into your amp inputs. So it is good for a single source, or you can plug your preamp into them to attenuate the gain on it (which is what I am doing now, although my DAC sounded very nice through both attenuators). I have not yet tried the Goldpoint or Luminous and based on what I am hearing now from the nude attenuators I may not. While the passive attenuators I have tried to date are very transparent, they are very much dependent on the type of attenuator and resistor being used. System matching with the right resistor is important, which is less the case with a transformer based passive. The EVS uses a 10k Vishay and the Endler a 4k Yageo. Both, while transparent, impart a signature by virtue of the choice of resistor being utilized. The EVS are smoother, while the Endler are bit brighter (perhaps forward is a better choice). Each are very good attenuators. From what I have researched about Goldpoint, the ladder type attenuators are best, but that is more practical in a box versus nude version.

The Welborne Labs unit is interesting in that it is a remote controlled stepped attenuator. I thought about getting it, but as you will see below I was convinced of another option.

I have also looked at:

Space Tech Lab
K&K
Electra-Print

These are transformer based designs. I tested the Electra-Print and it did not work in my system. This unit operates like a step-up and comes in different ratios. For whatever reason they sent me a unit with a 1:8 ratio versus what should have been a 1:1 ratio. It was just too hot on the volume control with my DAC. I suppose I could have gotten them to send me a 1:1 version, but after more research and response to my discussion thread (on the Goldpoint), I decided to buy the K&K, which is a custom built model. I already use their ste-up for my phono stage, so I'm familiar with Kevin Carter's work. Also, the design of this passive uses the same S&B transformers as the Bent (which I like and which I hear may be re-introduced shortly). The model I am getting will have dual volume and selector switches (Seiden from Japan). However, Space Tech Labs could get a shot if the K&K does not work out. I was very impressed with Albert.

From what I have heard so far I like the passive approach, especially since I have a high sensitivity and high gain amp. I don't need all the extra gain from a preamp. What is left to figure out is if the sound is comparable to an active linestage. I'm thinking it can be, but like you I don't exactly know yet. I'll post my thoughts when I get the K&K.

The problem you have is that all passive devices will have an artifact unless they are directly at the input of the amplifier. The reason is that the interconnect cable, even if very short, plays a major role in the results that you get. Resistive passives cannot control the interconnect cable and so loose dynamics and bass impact at lower volume settings.

The problems that transformer units have are bandwidth and hysterisis loss. Hysterisis loss is a phenomena of transformers wherein it takes a little bit of energy to change the polarity of the magnetic field as the signal does the transition from one polarity to the other (this energy comes from the signal itself). The result is low level distortion and low level signal loss.

In either case of transformer or resistive control, if the sound quality changes depending on the setting than then you have a problem regardless of setting!

Unfortunately many active preamplifier line sections have enough of their own artifacts that passive devices are often preferred, but ulitimatly a properly designed line section will easily beat the best of the passives.

Atamasphere's points are well taken and basically boil down to the fact that many source components are not capable of properly driving the cables, passive control, and the input to the amp while at the same time resulting in enough overall system gain. However, if they can drive the load and you don't need the gain, why would you want to introduce more active stages into the signal path if you don't have to? The point most people miss in this discussion is that an active line stage also contains some form of passive volume control. Usually a potentiometer but can also be a stepped attenuator or transformer though the latter is rare.

The bottom line is that it is much, much easier to get an active stage to integrate into your system. They generally have a higher input impedance and lower output impedance than a passive unit which makes life easier. Each passive will have a different input and output impedance which will interact with the output and input impedances of your source and amp and dramatically affect the sound making finding a good match more difficult. If your other components are up to the task given the caveats above and you are able to sort through the myriad of choices I think a passive is the clear choice.

Atamasphere is correct that most people will get better results from and active, but that is becuase their system aren't properly integrated without one and they have too much gain. My position is simply this, a properly designed SYSTEM will have the fewest number of active components needed to get the required gain. Adding more simply to buffer the volume control will always result in degredation.

The output of my phono stage is designed have enough drive for a passive. The gain of it and my amp are more than enough to drive my speakers to very high volumes if desired. My setup permits the luxury of relatively short interconnects. It would be silly to introduce another gain stage.

I am currently auditioning both and agree that the resistive controls sound better at higher settings, but if you have so much gain that you must operate at the lower settings then you need to change something anyway as the overall gain of the active stages is too much for your speakers. At lower volumes I prefer the transformer units but since I don't listen much at those levels I am now leaning toward resistive.

Hi Atmasphere (Ralph?),

Don't active tube preamps face similar hysterisis issues with their own output transformers?

I have a DIY S&B transformer volume control and am very, very, happy with the performance in my fairly resolving system. I'm not wworn to any particular component design, but have found it very hard to match the TVC's quiet, transparency, tonal body & weight, and dynamics - especially at low volumes.

That said, my experience with preamps is nowhere near yours and I take your advice with great confidence. The only problem will be finding a preamp that significantly outperforms the TVC at a comparable <$700 price up to $2k.

BTW, congrats on weathering the storm with your company and keeping it where it should be - in your hands. I used to frequent your user forum a few years back and was always impressed by the satisfaction and dedication of your customers. You and your employees have forged a priceless bond with with them.