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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
georgehifi's avatar
georgehifi
4,966 posts
 
Hwv1 hi.
Thank you very much for your praise and very in depth review. And I'm not surprised it better your TVC preamp, as Shakeydeal also has said, as transformer (TVC/AVC) preamps have a problem as I've outlined to Milpai above.

Yes with any passive preamp or active tube preamp with their high'ish output impedance, when you try to simultaneously drive your main poweramp and a subwoofer amp/s, you create a heavier load for the preamp to see. And it's really only suited for solid state active preamps with their low output impedance to drive.

This problem is the same for any passive or tube preamp, and the way around it is to use a high input impedance buffer in front of the sub amp as you've done, as most sub amp have stupid low input impedance.

Cheers George
milpai's avatar
milpai
1,341 posts
 
George,
Can you point out, what to listen for in a music passage, so that some instrument/voice/etc starts to ring like a bell? I will listen to more carefully and see if my TVC does that.
georgehifi's avatar
georgehifi
4,966 posts
 

Like a metal dome tweeter without a Zobel network on it, they ring very similar and sound "hot".

And the proper word to call it is it's resonance frequency, "ring like a bell" is just slang.

That is why when the TVC is loaded down by a 1kohm load (in my posted Stereophile graph) it damps the resonant frequency out and creates a roll off instead, but then you also have an impedance mismatch.

Cheers George

lacee
811 posts
 
I can understand why someone would think that a passive pre amps and a LSA are lacking something compared to a tube active pre-amp.

It's the noise that is seldom ever noticed until it's gone and if you've made the mistake to feel that the pre sounds fuller than an LSA then I think it's the added noise you like.

When I speak of "noise" I mean the stuff that encrusts the music like a spiders web.

You hear the music, it sounds good.
Clean up the noise and the music sounds anemic, threadbare, fatiguing, sterile, pick any term you like.

But it's just the absence of the noise that was filling in the cracks that made the sound "smoother,fatter, sweeter" or pick any term you like for pleasant distortions we all live with and accept.

When you start to rid your system of the "noise"by cleaning up the power from your panel to your gear,and doing the tweaky things that just can't make any difference, you begin to hear your system in a new clear and cleaner light.

You can then more fully appreciate how a clean sounding passive pre (or better yet an LSA) is doing such a great job of not adding any more noise to the system.

I've just done some more tweaks involving Nordost QV2 and several Stillpoint ERS cloths throughout my system.

I can add that the system has never sounded better, and that the LSA is adding nothing to detract from the sound.

Did the sound become more threadbare by eliminating more of the "noise"
No.

What I notice is more detail and space between the instruments and vocals.

The space that was filled with noise isn't .
It just space where there should be space and music where there should be music.
The two are not entwined together in the spider's web.

More than ever I feel that noise is being accepted as part of the sound of some systems that are described as warm, musical and smooth.

And when absent some folks miss it.

They blame the new school of audio design as having lost it's way , lacking soul and of ramping up the treble for the sake of all the old audio farts etc.

The LSA is noise free in my system.

And that's all that I want from any component.
A component that neither adds nor subtracts from the music.

I wish there were more components like the LSA.
georgehifi's avatar
georgehifi
4,966 posts
 


Very well put Lacee.

Just two words sum it up "BLACKER BACKGROUND"
This not only improves dynamic range as it lowers the perceived noise floor, but gives you space between notes, as well as transparency to the sound.

Cheers George
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