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

Showing 4 responses by john47

Most modded LSA: don't know.
Probably need to follow DIY.com to get a sense of yes or no.

Maybe the power supply is the big one!
Sorry part of my earlier post was premature.

"I’m using the original supplied wall wart psu, so your discussions re power supply are v interesting. Seemingly its sm according to George's suggested AM radio test, which gets noisy brought close to it."

I believe I misinterpreted noise: George's info says he supplies a linear 12vdc supply - thats what I've got. Please ignore my "Seemingly its sm," line.
Thanks for your comments George: no I didn't have a wall wart, I would have bought the package, so can about guarantee mine is a 'George' psu.

Banquo
"John47: did replacing the rca's make an appreciable difference?"
I would like to say yes, but being semi ancient and not keeping notes I don't remember. It was some time ago, but can say that my system sound has gone incrementally forward (over time). If there was no difference, or worse, assuredly I would have a big mental red alert.
Of note - I've used Nextgen Ag throughout, to match my silver ICs, and that I discovered (by removing) gold plating adds warmth, ie colouration I don't want. Expensive, but a oncer. Best RCA? I cann't say, but I read heaps before I bought.
Further: WBT Nextgen are not a direct replacement in the LSA, the mounting holes need enlarging, not straight forward.
Sorry if above seems like a non answer, but I don't recall, even subliminally, thinking I should restore the original RCAs.
Hi guys: haven’t viewed this thread for a couple of yrs at least (since I bought a LSA, after the gracious, generous help of Pubul57, Clio09, and George).

Maybe you are interested: I upgraded my LSA by wiring the power supply direct to the board (removing the psu connector). It was beneficial, but relatively so long ago I can’t be specific about what difference I heard.

Oh, I also replaced the RCAs with WBT NextGens to (supposedly) impedance match my WBT NexGen/ICs, and added a separate earth lug to the LSA chassis, that is wired (separately), directly to the green mains Earth wire behind a dedicated mains outlet (so the LSA is like a star earth in my system. I tried in vain to get George to add an Earth lug when I purchased).

(It gets worse! I also rewired my LSA with the same silver litz of my ICs.
But other than the psu wired direct to the board, it’s all far too laborious – I’m not even sure I should mention it!)

I’m using the original supplied wall wart psu, so your discussions re power supply are v interesting. Seemingly its sm, according to George's suggested AM radio test which gets noisy when brought close to it.

Thanks guys for the interesting posts.