Lightspeed Attenuator - Best Preamp Ever?


The question is a bit rhetorical. No preamp is the best ever, and much depends on system context. I am starting this thread beacuase there is a lot of info on this preamp in a Music First Audio Passive...thread, an Slagle AVC Modules...thread and wanted to be sure that information on this amazing product did not get lost in those threads.

I suspect that many folks may give this preamp a try at $450, direct from Australia, so I thought it would be good for current owners and future owners to have a place to describe their experience with this preamp.

It is a passive preamp that uses light LEDs, rather than mechanical contacts, to alter resistance and thereby attenuation of the source signal. It has been extremely hot in the DIY community, since the maker of this preamp provided gernerously provided information on how to make one. The trick is that while there are few parts, getting it done right, the matching of the parts is time consuming and tricky, and to boot, most of use would solder our fingers together if we tried. At $450, don't bother. It is cased in a small chassis that is fully shielded alloy, it gets it's RF sink earth via the interconnects. Vibration doesn't come into it as there is nothing to get vibrated as it's passive, even the active led's are immune as they are gas element, no filaments. The feet I attach are soft silicon/sorbethane compound anyway just in case.

This is not audio jewelry with bling, but solidly made and there is little room (if any) for audionervosa or tweaking.

So is this the best preamp ever? It might be if you have a single source (though you could use a switch box), your source is 2v or higher, your IC from pre-amp to amp is less than 2m to keep capaitance low, your amp is 5kohm input or higher (most any tube amp), and your amp is relatively sensitive (1v input sensitivity or lower v would be just right). In other words, within a passive friendly system (you do have to give this some thought), this is the finest passive preamp I have ever heard, and I have has many ranging form resistor-based to TVCs and AVCs.

In my system, with my equipment, I think it is the best I have heard passive or active, but I lean towards prefering preamp neutrality and transparency, without loosing musicality, dynamics, or the handling of low bass and highs.

If you own one, what are your impressions versus anything you have heard?

Is it the best ever? I suspect for some it may be, and to say that for a $450 product makes it stupidgood.
pubul57
This thread has taken an amusing turn. Teajay, while you stated the obvious about George and this thread, he and his LSA flag wavers should be free to express their opinions. I have been a flag waver for different products out of enthusiasm over the years, and despite poor execution at times, the flag waving still has merits even if it is ugly. In the midst of this rather tribal discourse, useful information about the realm of passives has come out. I have always tried to keep an open mind in audio so as not to get stuck. If dynamic pre-amps are a dinosaur and sonically redundant, so be it. I am not wed to my equipment.

Audiophiles, despite throwing around a lot of pseudo-scientific jargon and technobabble, are often very undisciplined when it comes to testing equipment. Has anyone done a blinded comparison of passive units? Can anyone tell the differences between a LSA and a Truth passive behind a curtain? Would the lay public be able to say "wow, that one sounds SO much better..." I am doubtful.

I blinded my wife and had her listen to the Dude and LSA, and the differences were stark. I will readily admit that my system may not be LSA friendly. The impedance of the Samsons (68K) is ballpark based on George's parameters, but they are SS. My speakers are also not super sensitive and employ Scanspeak drivers. If I could intuit my way into the ideal LSA rig, it would be sensitive speakers (like Clio's), tube amplification, and warmer cabling (like Pub's)????

George, I tried to ask a few more technical questions earlier in this thread and and you failed to really address them and simply referred me to the DIY site which I did peruse. So, boil this technology down for us in a few sentences or less. In terms of material science, does Cadmium have a sound? Is that part of the reason why it is perceived as superior to carbon or metal? What specific measurements or measurable parameters separate the LSA from other passives or active pre-amps?

Marqmike, you made some interesting points about music and perception. I played music as a kid and come from a musical family. I have a reasonable framework for what things "should sound like." The thing that live music has that I crave for in my system is dynamics transients and an energized ambience. Any pre-amp that inhibits that, passive or active, is out in my books.

Finally, I have to comment on George's reference to testosterone. Testosterone and Audiogon or testosterone and diy don't really go together. They are like oil and water. Spending this amount of energy and time snipping back and forth about a volume control is not in the domain of manly men. I think if we all got hormone replacement therapy (and were treated for obsessive, compulsive disorders), Audiogon would start to wither....
"Would the lay public be able to say "wow, that one sounds SO much better..." I am doubtful." When it comes to preamps, amps with sufficient power to drive the speaker, and cables of any ilk, I would say you are 100% right. The difference between speakers however (and room placement) would be pretty obvious even to the most leaden, "untrained" of ears.
Disciplined testing? I don't know. Just kept switching between preamps with the same 2-3 "test" tracks for a week, over and over, brought audio buddies over to minimize the possibility I might be hallucinating, and I (we) enjoyed the LSA every bit as much as much as my relatively expensive tube linestage and so I decided to save the $7000 and not worry about tube replacement (I have enough of them to worry about). Not science exactly, but enough to make a decision. Hard since the linestage is probably the #1 recommendation by the speaker manufacturer for his speakers and the one he uses at shows, and I certainly loved it - but still....I also have no phono, and no switching requirements.
I would like to test the LSA against the $16,000 Music First Audio Reference Passive. Not sure that is going to happen though. Wonder if it includes an IWC for keeping time.
Paul, I agree with all of that. Speakers and room are easy breezy. I also readily admit the the blinded A/B thing is hardly scientific in my hands as I have no dedicated switching device, etc. Most posturing on my part. lol. It was very "scientific" of you to included friends in your decision. That is good enough for me. I include my wife in all audio decision-making to protect me from me and my strong abilities at self-deception. That being said, it would be an interesting exercise to see if you could discern specific personalities of the passives discussed thus far.

I am not familiar with the music first piece. Does it make espresso as well?