If the rest of your system is passive preamp friendly (impedance, sensitivity, low capacity speakercable), you can get very good results.
My Bent NOH (transformer based) outperformed my Sonic Frontiers Line 3......
A passive is not for everyone or every system. However, I will enthusiastically second the Bent NOH. It is the very best linestage I've heard with my McCormack DNA-225 and I've had a few. Most recently, it embarrassed a Pass Labs X1, which is about three times the price.
The NOH is ultra transparent. Some may find a passive lacking somewhat in dynamics. I experienced this with a Placette and a previouslt and earlier Bent 102. However, the NOH delivers it ALL. Good luck.
I agree with 4yanx. The Placette was thin, lacking dynamics, and uninvolving in my system. My current preamp is a custom job using the same trannies as in the NOH. It is excellent and has bested many more expensive preamps in every respect, including dynamics and bass response. I also agree with his disclaimer about passive devices, even a TVC, not being the best match in every system. But when it all comes together, it is magic.
reading the review by audiotweaks on the bent audio site www.bentaudio.com will give you an idea of the requirements for passive volume control,the resistor formats series,shunt and ladder, and the transformer alternative.www.audiosynthesis.co.uk description of the passion 8,also lays out the ideal requirements for a resistor type.I have both a synthesis and a bent noh both sound wonderfull but my system at present suits the noh which is available with either copper or silver tx102,s a chat with john chapman about your system would help to choose the correct type of transformer for you.If you do choose a resistor type at least look at audiosynthesis they are the uk distributers for vishay bulk foil reistors,neutrik connectors+they also manufacture high quality silver cables and all of their products feature these components.Also their fit and finish is of the highest standard.
Here's another vote for the NOH. With the right amps in my system it has outperformed a SimAudio P5, an Audion Premier and a Canary 801. It has clarity, dynamics, low-level listenability - there's just less getting in the way of the music.
I don't know if it will run with the REALLY big dogs - the CJs, ARCs, VTLs, CATs and Lamms of the world, but I can't see anyone being disappointed if the rest of their system is sympathetic - especially when the price difference stays in your pocket.
System matching/synergy is key as usual. Need enough juice coming out of your source and decent gain and input impedence in your power amp. The Bent NOH is transparent, detailed, extended, with just an ever so slight hint of sweetness that makes you forget about the gear and let you enjoy the sound.
Have any of you Bent users heard the Sonic Euphoria PLC? I'm curious about this unit because the Bent is no longer available, and because they have a 30-day trial period.
Also, roughly what conditions would contraindicate a passive?
I had the Sonic Euphoria and liked it a lot ... butthe First Sound Passive Preamp (Reference II) was a tad better resolving complicated passages.
Hope this helps
Thanks. Apparently the output transformers in my modfied CDP would not be a good fit with the Sonic Euphoria, which has an input impedance listed as 500-1000 ohms. Perhaps all passives need to be ruled out.
Anything with real transformers, as opposed to autoformers, should work. The TX102 trannies in the Bent have an input impedance of 10K to 250M ohms. They should have very little problem with any real-world source impedance. This is in marked contrast to resistor or autoformer passives, as is the very low output impedance, which is in the single-digit range over much of its travel.
I have found no constraints to the use of my Bent other than power amp gain. A pair of amps with low input sensitivity (~2v+) didn't have the dynamics when driven by the Bent that they did with active preamps. Amps with more normal sensitivity (1.5v or less) sound better with the transformers than with any of the actives I've tried so far.
I'd say to keep looking for a passive with transformers, either the S&B or Sowter.
I would like to know what amps and CD/source components you who say the NOH was so good were using? My experiences with passive preamps (McCormmack TLC,Pass Aleph L/P, and others) has been dissapointing from a dynamics stand point...at least with the combo's I've ever been associated with.
I'd conceed that maybe there's some impedence matching issues, but not sure.
Any recommendations? I've tried passives with everthing from a few Tube amps, to Classe's, to Threholds and Pass Labs, to Coda's, McCormmacks, Meridian's, and more. I've yet to get dynamics like I do from a good active 2 channel pre in my tries over the years. And, for the same token, I've never heard dynamic results (although clear and detailed) from others passive combo's. Maybe someone could steer me to some source/amp combos to try.
Sure....I'd try the passive route again if I knew I could get my dynamics I so crave.
Thanks. I'll look for a used Bent then.
I am an owner of the Django and bent passive. They were superior to my Hovland HP100, until I got the Space tech lab 113. Better in every department bot least focus and bass.
Has anyone heard the First Sound Passive Preamp and compared with any of the TVCs on the market since the last post here. Quite a while, due to many threads on passives, but this seemed as good a place to ask as any other.
I have heard it. It is nothing special sound wise in terms of comparisons to other resistive passives. Better build and quality of parts though IMO versus other resistive and even most magnetic passives. Especially if you can find one with the Shallco attenuators. I guess at the used prices they have been selling for lately one could do a lot worse.
At the time I did comparisons with the First Sound I was still convinced my TVC was better. It would be interesting to compare one to my autoformer and LSA.
You mean the TVC that became my TVC?
Yes as a matter of fact that TVC.
Well, when you find something better than the Lightspeed, let me know:)
We're working on it. I still need to get you out one of our MLA's to listen to. If I get off my butt and build the balanced one I've been planning I'll let you try it out. Not sure I would say the MLA is better than the LSA, but it is definitely different. The LSA is just downright unique in it's simplicity and sounds so good.
Is there balance control with the MLA, or just tight mathcing between channels. I think we might be both of the mind that channel balancing is an important "preamp" function, but most passives don't seem geared up for that.
The MLA can come with a balance control or it is available with dual attenuators which is another method you can use to control balance.
Interesting to hear Roger's changing view of resistors versus transformers, I
wonder what is causing that, but alas, another thread....actually, probably
relevant to the thread. TVC / Resistor and balance control are key choices for
the best passive. I think Roger used to be concerned with bandwidth
limitations with transformers versus resistors, but maybe transformer, or
autoformers, are getting better, who knows. Similar "debate" a Salvatore's site
in the passive line stage section. And then there is technical breakthrough of
Anthony can you explain the MLA a bit. It uses a transformer to act as a buffer of sorts, but resistors to attenuate volume? Am I getting that right?
The purpose of the transformer is to step up the voltage, not to attenuate. The 10k potentiometer or series stepped switch does the attenuating.
I've heard a few passives, but all had a reduced sense of dynamic swing...I much prefer an active preamp.
What does stepping up the voltage mean? What is the benefit? That has nothing to do with gain, right?
Actually it does have something to do with voltage gain. Depending on the ratio selected, assuming your source was 2V output, voltage gain could be stepped up to 4, 8, or 16V. Then you would attenuate the signal from there.
The circuit design loads the signal source op-amp letting it operate at its maximum ability. It is a completely passive design (no active circuitry, no power supply, or power cord), but unlike other passive pre-amplifiers, the MLA delivers a higher voltage at its output than it receives from the input. One benefit over other passive designs is the output impedance remains fixed which means that the frequency response does not change as the volume is changed.
The whole concept works due to the nature of how the hand built nickel core transformers are wound and operate. These are essentially op-amp loading transformers that cause op-amps to deliver current into an essentially pure impedance primary. The secondary then produces the equivalent voltage into hard termination which is now usable for the next stage of amplification.
So, like an active preamp it offers its own version of gain, but at much greater transparency and lower distortion levels. It does not use buffers. Call it an in-active preamp if you would. It is best used with digital sources under 600 ohms, but I have a high impedance (10K) input as well for use with tube and other sources requiring it. I also have used it with my phono stage, but it uses AD-797 op-amps for the output so it matches up better than other phono stages might. I'm working on a balanced version that will sit between my Otari Mx-5050 BII and Atma-Sphere S-30.
What are the issues that the Electra-Print Magnetic Line Amplifier is trying to address that the Lightspeed Attenuator does not - under what circumstances would that design approach be preferable to the LSA and other "simple" resistor-based attenuators, as well as AVC and TVCs?
It's not trying to address any issues per se. You and I are in the minority regarding our preference for a passive design over an active one. Stringreen made a comment in this thread that is shared by many audiophiles and designers. Especially when it comes to which design is better at reproducing dynamic swings. I happen to think the LSA, in all its simplicity beats active designs (actually the perception of them) at its own game. I think the MLA does too. It's a simple design with all passive parts that mimics an active circuit, dynamic swings and all (for those who believe an active circuit is the best at this). Two transformers, an attenuator (pot or resistor design, two if you feel dual mono is the way to go), and perhaps a selector switch if you want more than 1 input.
Perhaps the only benefit the MLA might have over other passive designs is the fixed output impedance and frequency response. Regardless of where the volume control is positioned those two specs are constant. You and I both know that is not true with other passive designs unless they are buffered, and then technically they aren't passive anymore. So the MLA might be easier to match in ones system.
I've been listening to the MLA, Truth, Silicon Arts Design, Slagle AVC, and LSA in my system for a while now. All of them are very good. Sure some do things better than others or work better with specific amps I own. In comparisons I'll hear some differences, but nothing that would lead me to think one is significantly better than the other. They're all a little different, but each is enjoyable.
Thank you spending all that time with all those topologies, and sharing your experiences over the years. I will give the MLA a listen, I'm sure is uses some very fine transformers, given the provenance:) Ultimately, I think the Lightspeed just fits my some system context to a T, so it might be hard to beat its inherent simplicity in terms of parts (but not so easy in excecution, as you know). I do think the dynamic swing issue is based on simply using a passive in a system that for various reasons simply needs an active to perform its best, and maybe the MLA bridges that gap to in terms of a greater degree of "universality".
The circuit for the MLA was originally designed to be incorporated into an integrated amplifier design, like the 45SE we had at THE SHOW in January. Not everyone has a need for a 1.7 watt flea amp though, so there are several out there being used as stand alone line stages and they work pretty well in that capacity too.
The transformers are tiny and you wouldn't think they would be capable of the task, but they are wound by one of the best there is at this art form.
Do you anticipate Joe will try an AVC/TVC as an alternative to using resistors?
You mean Jack? No, he is happy with his design and an AVC or TVC wouldn't work with it as the attenuator. It has to be a 10k pot, series, or ladder attenuator. When I built my AVC using the Slagle autoformers he was curious about them (for reasons I can't mention), but not enough to make him consider changing his design. Jack could easily whip up a few autoformers though if he had reason too. Plenty of resources to do it.