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
I've been using the LSA with a Spectron Musician for the past couple of months and I'm very very pleased with the results.
Teajay asked me that? That's odd - missed it. I use to think this site was mostly enthusiasts that liked blabbering to each other, but perhaps there are more commercial interests lurking in the woods that I care to think - nothing wrong with that if there is full disclosure.

As far as SS, I never tried it, and unless it was a 100kohm impedance load, I proabaly would not bother, something like the First Watt Alpeh J might do well, but for the most part, I see this as a tube amp device, though I imagine it has been used with SS and like Drubin some of them have found it perfectly suitable.

Disclosure: I paid full price for my LSA.
Don't mean to suggest with an amp with less than 100kohm input impedance, rather that would be my personal pridelection - I'm sure Goerge would point out that 47kohm and up should work fine. Of course you would not have any tubes in the chain and I would only use a SS amp with a tube preamp - something always seems to be missing when there are no tubes involved - I don't like it nearly as much.
If Teajay asked that of Paul I certainly missed it too. Not sure why it's even logical to ask of either of us. In any case I have no business relationship with George.

I'm not attempting to design and sell tube amps, I am actually doing it, preamps too, and step-up transformers for MC cartridges. How that factors in here I'm really not sure. However, per Audiogon rules I disclose my business affiliations when required.
I have had my LS now for over 2 years and can thoroughly recommend it for its clear, transparent sound. I use both integrates and pre- amps and since buying the LS, my favourite pre being the Melody 1688 has sat in its box due to non use. I sometimes tend to have short listening sessions and warming up a tube pre is inconvenient.

The LS having only one set of inputs hasnt been a hassle as I use a multiple input phono stage but when I do need to change source say to CD its a little hassle unpluging and repluging new interconnects. For the price differential compared to a full blown multi source pre that sounds as good, its not a hassle at all.

George, if you made a dual/multi source LS then the world would be your oyster! cheers Michael