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
Devilboy, Photonman seems to have found so nice low capacitance ones,

Quote "I am using a 3 ft set of Bryston IC's (Canare and Neutrik) which are 21 pf/ft into the LSA and a 2 ft set of Blue Jean IC's which are 13 pf/ft out of the LSA to amp."

These are very low, I myself have not used Mogami so I can't comment on them, but if they are below <100pf per ft they should be fine, any cable manufacturer worth his salt should know this spec, and they should be made to advertise it in their specs on the packaging.

Cheers George
I have the Blue Jean LC-1 which is 12.2 pf/ft.

$31 for pair of 3 footers or $29 for 2 footers.

The Brystons I already had otherwise I would have used all Blue Jeans.
Oops, sorry George. It appears I got you confused with Clio09. Thanks to all for responding.
George - to implement a pair of subwoofers, what do you think to use a Y-splitter at the RCA outputs - one set to speakers, one set to subwoofers?
This can be done Nguyen, as it is how I run it, bi-amped, both amps are 100kohm input impedance, Lightspeed sees half, 50kohm, same difference.
The thing to look at is the combined input impedance of your main amp and the subwoofer amp.
If your main amp is say 100kohm and your subwoofer amp is 100kohm then the Lightspeed will see 50kohm again this is fine.
But if your main amp is 100kohm again and your subwoofer amp is 20kohm then the Lightspeed sees 16.6kohm not so good.

Cheers George