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
Hi Georgelofi,  I talked to Joe there at audio advisor,  he said that the Vincent pho 700 does 8 volts max out put,  your unit is passive?, I may put  this on my modified krell 700cx to play with from time to time,  it's 100kohms, however,  it takes 3.35 volts to push,  as you know, I've been pushing that amp with 2 volts running directly from the digital player,  cheers 
Yes, that 700cx Krell has low sensitivity as stated by Krell at 3.58 Vrms to give it full output just before clipping Most amps are usuall 1-2v. Your lucky the phono stage has so much output 8v (which I think is peak/peak anyway) not rms.

Well even with 2v from your CDP's and you still get enough volume, all this speaks that you have no use for and active preamp/s with their even more gain and colourations.

Cheers George  
Post removed 
Thanks for bumping Glory, no not dead just resting.

I’ve been on an extended holiday from any production runs, as they can be very taxing/monotonous to produce, just quad matching all the led/ldr’s can do ones head in, as to keep this kind of pricing I run basically a one man show.

Got a few orders and half way through finishing off the next batch to go out.

You should maybe get some more happy owners posting their thoughts if they are members of Audiogon and frequent these pages after they’ve had a good listen, but then most of the next batch is going to Europe and Asia, I don’t know how wide spread Audiogon forums go outside of the US. They seem to have their own go to forums in these areas.

Cheers George