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
For those interested I posted the light loading question over on Audio Circle under the Music Reference section:

Music Reference RM-10 Light Loading
11-02-10: Pubul57
>But there is no output impedance optimization based on dial position 10-12-2 o'clock - is that right? Some attentuators seem to have optimal positions in that sense.<

Anywhere between minimum and 3-o'clock is good if i/o impedances are met. If it's after three o'clock for normal level listening in a system then (cdp/amp)has a gain shortage, or ridiculously inefficient speakers (80db or so).
I have a friend that has JBL4350's and Array 1400's and his 80watt Transcendent OTL monoblocks just have enough power driving the 4350's full range but the bass is seriously lacking, but they do sound good on just the upper bass, mids and tops. As for the 1400 Array's they can't even drive the mids and tops on those let alone the bass as well.
Cheers George
I've bought George's Lightspeed and am (im)patiently awaiting him to build it and ship it half-way around the world to the frozen Canadian tundra. Build George, build . . . It'll be connected to an Art Audio PX25 SET amp driving 97dB efficient speakers - hope it sounds as good as others claim.
Kevin, what preamp will the LS be replacing or compared to? The Art Audio doesn't have volume control, does it?
Mine was delivered today. Transit time was 15 days to USA. George shipped within 2 weeks as promised after placing my order. It's nice to deal with someone with a HONEST and accurate estimate. No BS why estimates are constantly revised ... blab blab blab

I bought it out of curiousity and also been looking for a non tube preamp for the summer that is good enough that I will enjoy. Initial impression is VERY VERY positive.