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 source and its various meanings as related to the LSA:

1. The live acoustic performance. The LSA, and no preamp, has anything to do with this. That event cannot truly be reproduced and perhaps the biggest drop off from the source in this sense occurs in the recording process itself and affected by colorations/distortions/mixing etc caused by the microphone chosen, the electronics, as well as the manufacturing process of the medium that we do bring home. This is the truest "source" - the "absolute" sound?, but preamps (and systems) do not touch it since it is mediated and never really comes home with us.

2. The recording and the information embedded in the medium - digital or analog. This is the limit of the musical information that can possibly make its way through our gear to our speakers to our ears. This contains all the musical information that is possible - including the ever popular audiophile attributes of soundstaging, dynamics, warmth, bandwidth and bloom. Any musical information you hear that is not inherently in the recording as embedded in media is a distortion and no part of the source as defined here. Pleasant though these distortion might or might not be, they are pixie dust that has been spread over the music and no part of the original performance mediated through the recording process - whatever they are, they are not part of the musical source. The LSA only touches this source to the extent that the 3rd-sense of source does not interfere.

3. Finally, the electrical signal coming from the TT or CD/DAC that has been processed from the recording embedded in a medium to an analog signal for use by a preamp or LSA. I think that this is the source that the LSA is true to. It is the only source that meets the LSA one-to-one. The LSA cannot improve upon either recordings or "players" and a bad recording, or a weak turntable/CD/DAC will reveal themselves through the LSA - in fact a poor recording or player might in fact sound better with a preamp less true to the "source" in this sense. The question if this is true of the LSA, that it is true to the source in this sense, is that what one wants, or should want, in a preamp/volume control - is there a right answer?

CAVEAT: The LSA, will not be true to the source if it has insufficient gain from the source or sensitivity in an amp, or if the output impedance of the source and the input impedance of the amp are not appropriate, or if long interconnects have so much overall capacitance as to alter the frequency spectrum of the signal sent to the amp.

Now, just because the LSA may (subject to debate)may be as true to the source as a line stage / volume control can be, that does not mean that everyone would prefer it to something less true - not sure the answer to that can be decided by measurement and engineering, only listening and drawing our own conclusions about what we like.
Deep is right, but I love it! Good stuff and we are getting closer to the truth. I think we all "get it" to be frank and we are just starting to communicate.
This is the part I like ...

"2. The recording and the information embedded in the medium - digital or analog. This is the limit of the musical information that can possibly make its way through our gear to our speakers to our ears. This contains all the musical information that is possible - including the ever popular audiophile attributes of soundstaging, dynamics, warmth, bandwidth and bloom. Any musical information you hear that is not inherently in the recording as embedded in media is a distortion and no part of the source as defined here. Pleasant though these distortion might or might not be, they are pixie dust that has been spread over the music and no part of the original performance mediated through the recording process - whatever they are, they are not part of the musical source. The LSA only touches this source to the extent that the 3rd-sense of source does not interfere"

This sums it up nicely thanks Pubul57. After that, as stated, its personal choice as to what one does with this information - Colour it, reproduce it as "accurately" as possible or any variation in between.

If accurate reproduction is the end goal and the LSA is in the chain, then everything else has to be (a) Up to that standard, or better and (b) Optomised to work together in terms of impedance and gain.
I quote, or at least paraphase, both the great Winston Churchill and Lewis Carroll about what this thread has turned into regarding its "deep" philosophical/epistemolical search to unlock the ultimate truth regarding this topic:

" Never before in the history of high end audio... have so many ... received so much jabberwocky ... from so few."

Reading this thread is becoming more fun then watching Monty Python's, Meaning Of Life. Thanks guys.
Twas brillig, and the slithy toves
Did gyre and gimble in the wabe:
All mimsy were the borogoves,
And the mome raths outgrabe

Now where is that martini?