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
My interest in passives started when I read on Arthur Salvatore's website "if your source is up to the task of driving your amp(s), then no active linestage, no matter how good it is, will ever equal the sonics of your direct connection (or an equivalent passive)". This coming from a tube-centric audiophile made me ponder this for a long time. He goes on to describe the circumstances under which an active linestage would be needed. I read this and left this continuing with my various tube linestages, not sure if it was warmth I was looking for, but certainly dimensionality which I always found lacking in SS preamps.

Then I bought a couple of amps from Roger Modjeski, the Music Reference RM9SE and RM10s. Knowing he could design anything he wanted to, I noticed that he made the move from active tube linestages to passive and asked him why, this guy obvioulsy loves the sound of tubes, not only making gear with tubes, but also the best tube tester on the market, and he said just what Salvatore said, no active line stage would be better than a high-quality pot based passive with his amps (100kohm input, and high sensitivity). Asked about buffers, tranformers, blah, blah, and he said I can make you whatever you want ("I'll put a tube or two in it if it makes you happy"), but he repeated, nothing will be beat a passive preamp with no buffer IF mathed correctly between source, cables, and amp.

As to Fiddler's comment on warmth and dimensionality, I have to say we all want dimensionality (as long as it doesn't come at the expense of timbral accuaracy)and in this aspect I do not feel any loss of this important aspect compared with my Joule and Atma-sphere preamps. The area of warmth is a little more difficult to put my finger on, perhaps more subjective, and prone to the influence of preference. I will say that he idea of "adding" warmth is not something I am comfortable with, but that is just me, with the LS I feel I am getting as much warmth or lack of it as is in the source. The apparent warmth will vary with the recordings, and that is a very good sign to me, that is when the sonic attributes of a piece of gear change, or is dictated, by the recording - it tells me the gear is not putting an overlay over a recording that can be heard regardless of what one might find in the recording itself.

What I find with the LS is that the issue of soundstaging, dimesionality, apparent bass and highs, etc. is dependent on the recording, and for my approach to building as system, this is the way it should be, but that does not mean it is eveyone's cup of tea regarding the sound they are looking for.

But, these are all words, which don't mean a thing compared to trying one of these things in your system, knowing, and accepting, its ergonomic (one input/output) and electrical (gain and impedance matching) limitations, and judging for yourself.
I would like to build one, but include an output buffer (tube or FET) for driving long cables or low impedance loads. Of course a little gain wouldn't hurt either - especially for low sensitive amplifiers or if using a low MC cart (etc, etc).

I know this destroys the purpose of a 'passive' preamplifier - but I've never heard a passive that I've liked long term.
I have a passive in my system now based on a 50k tkd attenuator. I don't hear any obvious problems whereas when I had Endler type attenuators in the same system and interconnects there were obvious frequency anomalies. So how can one predict whether the Lightspeed will be an appropriate match?
For those of you who have been around the boards a long time, this looks very much to me like a much hyped passive preamp of old called the Morrison ELAD. I remember the buzz - the ELAD was the closest to "straight wire with gain" that you could get. I bought one. Well built but sonically did nothing for me. Fast but cold. No emotional connection. However it was good lesson. I learned that I prefer the warmer sound an active preamp over uber transparency.

I have not heard the lightspeed so I don't want to be critical. I hope its owners are happy. I will say that the price point makes it attractive to try out. $500 these days in audio is not much of a gamble. Just seems like we may have been down this road before.
I agree with Dividedebytube (interesting username)

Can this be used as part of a glorious active tube preamp? This would be the attenuater part? My very strong hunch is this unit will end up falling short of my current active tube preamp for the same reasons given by Fiddler.