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
You know Anthony, it just might be that the LSA is what it is and the way it must be:) Some of the DIY community seems to be hell bent on "improving" the LSA - it's just possible it can't be done - without trade off - thought it would be nice to get rid of the ICs. One less thing, but as you suggest an added element of complexity.
The only other possibility is to put it inside the actual amp at the input. It would require enough chassis space, but it can be done. This is Ralph's approach with the passive attenuator upgrade for the M-60 amps and up in his line. Unfortunately not enough room in the S-30 or Iwould have opted for it.
To reconfigure it and have it so it plugs directly into the poweramps rca's, would be a nightmare to do. As there is no standard distance between left and right rca's on a stereo poweramps and then there's monoblocks to contend with.
You would have to make two independent Lightspeeds each with their own power supply, they would need to be about the size of a cigarette packet each, this would be hanging of the amps rca's, and because it's on the back of the said poweramps, they would need to be remote volume, so double the size of those cigarette packets and you have your nightmare.
KISS KISS KISS KISS KISS

Cheers George
George, I appreciate that you want to keep it simple but you already have that product. If something was created pretty much like you and I have described, it would be better, but it would not be as simple. But that's OK- there would still be a market.
Like I said two lager than cigarette size boxes hanging off each rca on the back of the amp/s, and a third power supply unit, you need a remote volume control as they would be behind the amps, then there's the problem of the remote receiver in both units not picking up the remote controls signals because they're being block by the amp itself.
Then there's the price, definatly tipple or more, I doubt anyone would buy it after you've tooled up for all this, like I said a nightmare, but for DIY'ers worth a shot to get rid of one set of interconnects.
Cheers George