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
So we wait Clipsal for the system context for you B1/LSA "shootout". Also for Anthony's assessment of The Truth preamp, which seems to be a hybrid between some of the desing principles of the B1 and the LSA. Other passive comments (Goldpoint, BENT, Prmoethius, and other resistor, TVC, and AVC comments welcomed). In my system with Music Reference RM10 and 9, the LSA is the best passive I have heard, and I have tried most all but for the B1 in my system at home.
Anthony, I've read the threads about The Truth preamp and it does seem to employ a similar "volume control" as the LSA (photo cell versus optocoupler, not sure if that makes any audible difference)along with input and output buffers. When I spoke to Roger Modjeski about his passives, as you know he has a plain Pot-in-a-box and also makes a version with a tube buffer stage, I asked him if the tube buffer version would be better, he said only if you need a buffer, otherwise the the the version without a buffer would be better. So it will be interesting to see what you find when you try The Truth. I suspect that since my system is in no need of a buffer, the LSA would like be the better choice. It does not seem like you need a buffer either, so your observations apart from "theory" will be interesting to hear.
What I am most curious about is how well The Truth preamp will drive the S-30. The LSA does drive it well, but I'd like to hear if The Truth will improve upon dynamics. The bandwidth measurements are off the charts with the Truth and the output impedance is a constant 2 ohms. Apparently the input impedance is too high to measure.

No risk to try it so we'll see.
George, obviously you could have made a buffered version of the Lightspeed, what are the pros and cons to that approach. What are your thoughts on buffering? Go Spain!!