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
The DIY diffuser write-up was helpful, but after looking at your system page I'm more interested in those wooden hemi cylindrical diffusers. They look great in the room.

Well at least the Sony has legible specs for the lay person. You are in good shape with the LSA so not to worry.
George - thank you for chiming in. Glad to hear that no sonic purity is being lost at 8-9 o'clock than further around the volume dial.

Clio09 - Hemi-cylindrical (polyfuser) diffusers are much easier and faster to make than Skylines of similar size. Email me if/when you wish to consider tackling them.

Happy listening all.
Can you guys tell me how the compatibilty would be in my setup?

Quad CDP2-99 / 2.4 V rms max output
ASL 1009 dt / 100k / 1v input sensitivity
1m & 1.5m TG audio hsr ic's and speaker cables
Sonus Faber Guarneri

Much thanks.
You would want to use the fixed outputs, not the variable outputs on the CDP, but you probably already knew that. Atkinson measured an output impedance that varied according to frequency, but was in the 120 ohm range so I'd say you're good to go considering the other information provided.