The best passive preamp

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.

Yes as a matter of fact that TVC.

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.

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.

The purpose of the transformer is to step up the voltage, not to attenuate. The 10k potentiometer or series stepped switch does the attenuating.

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.

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.

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.

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.