Transformer based passives vs passive stepladder

Although I have a very well reviewed preamplifiers, I have become intrigued with passive approach to gain control. What caught my attention the most is the uber expensive Audio Consulting Silver Rock transformer passives. But then, I also see other companies making passive stepladder or simple passive volume attenuation( anywhere from $199-1000.)

Some of the transformer based attenuators seem to be Audio Euphoria, as well as the DIY or completely built Tjango, and the now discontinued Bent Audio unit.

What gives? Is all that has been said true about transformer based attenuation? Has anyone heard the Silver Rock?

Paul K
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:

Welborne Labs

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

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.
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.
Atmasphere - so are you saying that EVS and Endler, by virtue of the fact they are passive attenuators at the input of the amplifier, are immune from artifact associated with other passives as a result of eliminating the IC?

Bear in mind I love my active linestage which is a Joule Electra LA-100 MkIII. I'm just trying to rid myself of the issue where there is too much gain in the system. With my analog set-up the Joule, my amp, and phonostage provide ample gain and I have a lot of flexibility on the volume control. The digital set-up is a bit different. The passive approach here seems to be necessary to get what I need.

I do have one other option. Perhaps sending the unit back to Joule and having them reduce the gain on the CD output could be a solution. This would eliminate the need for a passive attenuator at the amp input.
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.
The problem is that you have to control the volume somehow. In active line stages and in the case where the passive is at the input of the amp, there is no interconnect cable that has to be controlled. It does seem that the interconnect cable (in tandem with the input impedance of the amp) is playing a huge role.

Problems come in if you want a different input and to a lesser degree if you have monoblocks. Passives make this inconvenient. A proper line state OTOH *should* allow you some distance from the amplifiers plus provide switching capability.

Back in the old days there were standards for input levels and the like, but that seems to have gone out the window with Digital Winter- almost as if digital would be the only thing you would listen to, so many CD players and DACs have high voltage outputs as they are intended to drive the amp directly. Its a hubris of sorts (it may be Digital Winter but I find new LPs all the time) and you wind up with too much gain if a line stage gets interjected. I understand that money is always an issue but it remains true that you get what you pay for. I wish more digital gear had jumper switches like the Wadia stuff that would allow you to select different output levels- it would make this stuff easier!
Thanks for the clarification Atmasphere.

In the case of my S&B TVC, I run true balanced output from the transformers and balanced interconnects to Jensen JT-11P4-1 input transformers which do the conversion back to single-ended for my amps.

Except in the case of my fully differential DIY Audiotropic PP 7591A amp which takes balanced inputs directly into the 1st stage.

Cable length/impedence and noise don't really seem to be a big factor here as long as my sources are capable of driving my amps.
So, Clio, you also find too much gain in some sources, such as CD using the Electra? I find that pseudo passives such as the active First Sound Paramount I use have the same issue. Usually is fine, with LP or Phono preamp through (low gain) but when it comes to CDP or other sources, sometimes it can get loud too fast. I wonder if this is the implementation of a preamp with OA2 tubes paired with 6922 or something else. The fact is that I have come to the realization that I have plenty of gain and that it can distort the original way things were recorded. I also have a pair of EVS nude Ultimate Attenuators and it does the job of attenuating the gain as transparently as possible, but how Atmasphere has already stated, sometimes, pursuying the last bit of purity sometimes has more drawbacks than benefits....

Nevertheless, I still dream of have one less stage, if possible in the signal chain.

Has anyone heard the SILVER ROCKS somewhere?

Paul K
Paul K - Funny, the Joule uses OA2 tubes as well, along with a pair of 6EM7 in the power supply. The signal path has a 5751 and 6350 for the mu follower. It is a pretty low gain preamp, but my amp is 30db and .8V sensitivity. I also have no issue with the phono preamp. Perhaps the EVS is the best solution for me at the moment, but I'm pretty curious at what my custom K&K will do.

The Silver Rock passives look nice, but they're out of my price range.
Based on my experience I'm inclined to believe Atmasphere regarding the role interconnects play in a passive configuration, as well as the inevitable artifacts generated by most active line stages. I have a Bent Noh with S&B TX-102 trannies, and while it is a very smooth and uncoloured device, I've never gotten it to work really well with any of the amps I've had. By "really well" I mean combining that smoothness and even-handed midrange frequency response with a sense of dynamic life, air, microdetail and enough bass extension. In contrast, the mid-priced tube line stages I have (Canary and Audion) give the music back its life and dynamics, but at the expense of some frequency colourations - and the level of detail is very dependent on the tubes in use.

Up to that point its a fairly even tradeoff of tastes - you pays your money and you takes your choice. However, a really good line stage like the Tom Evans Vibe/Pulse shows up both the passive and the tube units very convincngly, providing the best of each camp with lots of detail, transparency and musicality, while inflicting very few colorations on the sound. I have no doubt higher end tube units than mine would show a similar level of performance.

Passives for me are renewed evidence of the TANSTAAFL principle - "There Ain't No Such Thing As A Free Lunch".

Do you know which version of the S&B Transformers your Bent has in it? The mkI & mkIII versions are supposed to be noticably superior to the mkII.

I really haven't noticed any of the problems you mention going from my phono pre or dac to my Art Audio PX-25 or Welborne DRD 300B amps.

But, I am very, very, interested in Atma-Sphere's fully differential MA-3 preamp with built-in phono stage.
I do believe mine has the Mk II trannies. I think whether there are problems or not is heavily system dependent, but I get the impression that synergy problems are more widespread than gets reported. In my local high-end ecosystem everyone who has tried separate passives of either type has ultimately gone away from them due to problems with dynamics, bass/treble rolloffs and lack of detail. Off the top of my head that would be about six people.

The one fellow who is happily using one has an integrated with a passive volume control. This hints at the role of downstream interconnects in the picture. I have a stepped attenuator on my Audion PX25, but that amp sounds much better with an active line stage driving it. This points to the role the source component's capability plays, since the probable culprit is the source's output impedance.

That adds up to too many variables for this old urban cowboy. I'm much more inclined to put a very good active in the system and stop worrying about it.
I have happily owned a Silver Rock for the last 4 years, and it is, by far, the best sounding volume control I gave used. I bested a very nice custom made stepped attenuator- tube output preamp, along with, over the years, Levinson, VTL, Placette, Spectral preamps; the most expensive of which was $15K. One of the few things in my system I have never felt the need to change, or at least improve upon.