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
@ clio09, Thankyou, you are a gentleman!,You also proved to be a great asset here for me, I will take a look at the threads you posted here,again, Thankyou so much!
@ clio09, I have not told you, my amp only has balanced and Krell cast inputs,no rca single ended inputs!, can George make a lightspeed with balanced connections?,The praise here on this product is worth while to buy and try!, To use it I have to have balanced connections, I see this thread started in 2010, and George might now 2013 have available balanced???,,Whats your advise?,, cheers!
If no balanced LSA is possible, you can easily get a cable made with XLR/RCA terminations but you will not be balanced anymore but so what :)
The LSA is not available in balanced configuration. George has stated several times that in his testing a balanced design was not reliable. As Photonman advised just get an RCA to XLR cable, but keep it short, 1.5m at the most and ensure the cable has low capacitance.

FWIW I have a Warpspeed optocoupler passive preamp that uses LDR technology. It is balanced but is a more complex design than the LSA. In comparison I found both to provide satisfying results, but overall felt the LSA was smoother and cleaner.
I have tried very very hard to make a Lightspeed MkII balanced and reliable to stay in calibration even with electronic genius's trying to help out, but without some extra electronics (like sampling impedance values sort of feedback) it does have a negative effect on the sound quality, so it is not possible, and it would of put the price through the roof.
My old MkI Lightspeed design is possible to make balanced though, but it does not sound as good as the MkII. So your damed if you do and damed if you don't.

Cheers George