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
Hi James, I'm sure Alex mods the output stage and even the i/v stage of the Esoteric X01 when he does the mods, it is possible he has lowered the gain with his mod, also on inspection they are an opamp based i/v stage and opamp based ouput stage and it would be quite easy for Alex to give you more gain with these, just by jiggling around the feeback resistor value that are around each of the opamps.
James, I have a few of those Keith Jarret ECM CDs too. I get to about 2 o'clock on the dial using my Music Reference RM-10. Most of the "hot" CDs I have I get to about 11 o'clock.

Not an IC issue IMO. George might be on the right track regarding lowered gain on the source. Might want to ask Alex about that.
Hi everyone,

I stumbled across another lightspeed attenuator maker named Uriah Dailey whose product is called "Lighter Note Lightspeed Attenuator." 'Lighter Note' may be his company name - not sure. Here's a link:

http://www.buildanamp.com/main.sc

I don't know how it differs from George's Lightspeed version, but wanted to bring it to light (sorry for the pun) for those considering a lightspeed attenuator.
One type of passive I have not tried are the EVS and Endler types. While I get the idea behind why the LSA without contacts would be beneficial, it also seems that EVS/Endler approach might have some theoretical advantage, no worries about IC capacitance, no IC, two less IC RCA connections and I think EVS uses a single Vishay nude in the signal path. Any experience with these? Head-to-head with LSA?