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
This can be done Nguyen, as it is how I run it, bi-amped, both amps are 100kohm input impedance, Lightspeed sees half, 50kohm, same difference.
The thing to look at is the combined input impedance of your main amp and the subwoofer amp.
If your main amp is say 100kohm and your subwoofer amp is 100kohm then the Lightspeed will see 50kohm again this is fine.
But if your main amp is 100kohm again and your subwoofer amp is 20kohm then the Lightspeed sees 16.6kohm not so good.

Cheers George
I have had my LSA for two weeks now and I have to say this is one of my best hifi purchases in all respects.

Definite sonic value. It is just as transparent as my previous more expensive active pre but with less noise so my active is currently for sale.

This device has changed my attitude toward equipment purchases and shows that a little experimentation can yield pleasant surprises.

The LSA is the stripped down race car or race sail boat of stereo equipment.

A great novel product and worth an audition in any system.
Hi Photonman,

I have been using my LSA for a year now and thoroughly enjoy it. My experience is like many others on this thread and it is a permanent fixture in my system. In the future you might want to consider a battery power supply. Just when you thought it couldnt get any better.....voila!
Hi Seshkir,

Really, a battery supply? How does that work as I thought the power was only for the LED things? Does the light intensity or whatever change characteristics with the battery?

What is your battery rig consist of? Is it DIY project?

Thanks
As for use with battery, I recommend the use of 12vdc Lithium Li_ion rechargeables, these will give a couple of week use before needing a recharge. One important question you have to ask the seller is that the plug is 2.1mm and very important that the centre of the plug is + positive.
http://www.ebay.com/sch/i.html?_odkw=12v+li-ion+rechargeable&_osacat=0&_from=R40&_trksid=p2045573.m570.l1311.R1.TR2.TRC0.A0&_nkw=12v+li-ion+rechargeable+battery+pack&_sacat=0

Cheers George