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
You would think the real market for George's attenuator would be in licensing to other manufacturers for use in other preamps and integrateds. Virgin works well for me, but a combo with buffering when needed seems like the next iteration.
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I think it is patented, in fact I think George has already nixed one such attempt of using his design commercially without permission - but George could speak to that.
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What I did was to stop someone else from trying to patent it a couple of years back, what they wanted was for audiophiles to think it was their idea, but my first one was made back in 1974, using t/t and phono stages as the source, but they were not very reliable with the ldr's back then, lots of channel drift, and no led's I had to use low voltage bulbs. This was when I should have put a patent on it. As for now just the TM of the name Lightspeed Attenuator will suffice. And the small ego boost that the IP was mine all those 37 years ago (yikes!!!!). I believe as the manufacturing technology gets better they will be able to supply the Silonex led/ldr packages as perfect matched quad sets for stereo use and you will see the demise of the potentiometer with it's lightweight internal touch contact of a metal wiper on a carbon track , as they are the weakest link in the audio chain.
Cheers George