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
Wow! That has to be the lowest capacitance if any cable - no? But like George says, I feel safe with the 12pf/ft:)
I was rading a review of some VH Audio Power Cords" by Jim Merod for Of Sound and Music. I beleive he is a recording engineer - if that matters. in the context of that review he said something very appropos to the LSA experience, I why I love it:

"No superior power cord should "enhance" music by adding dynamic slam or transient bloom or etched imaging. Sometimes one may be tempted, hearing such artifacts, to believe that such "more" is good or better...or amazing. Such artifacts are exaggerations that distort or attenuate the relaxed vivacity of well-recorded sound. All audio equipment should be sold with a generic disclaimer: Do Not Be Fooled By Sonic Cartoons!"

I think the LSA is a "preamp" Jim Merod could love.
That has to be the lowest capacitance if any cable - no?
The extremely low capacitance results from the flat construction with wide spacing of the conductors. 300 ohm antenna twinlead has similarly low capacitance.

The lack of shielding could be a problem in some setups, though. Also, the relatively high resistance and inductance of the return conductors (compared to what a shield would provide) might also contribute to ground loop issues in some systems.

Best regards,
-- Al
I have a wallwart I purchased from Circuit-Test. It is 12VDC, 400mA, and is a linear power supply. Absent a battery PS which may sound better, is that all I need in an AC adapter?