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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
10,312 posts
 
Banquo363 The 1.2kohm for the phono is very high and should not be an "ideal" match with the Lightspeed, but it will not be harmful to anything either.
I have quite a few customer with dac's and phono stages with output impedances this high with tube output, and they say they couldn't care if it's not a 100% match as they are over the moon with the sound that they are getting with them into the Lightspeed Attenuator.

Cheers George
batalok
31 posts
 
Grannyring, my cables are diy. It consists of silver-gold (from Mundorf, Germany) with wbt-plugs, 1/2 m. Formerly it was 1,5 m. And the ss poweramps? I wish I knew, a "wizard" has done it, not me.
batalok
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banquo363
371 posts
 
Am I right in believing that non-ideal impedance match between phono stage and LSA results in a attenuation of the high end? Perhaps it hasn't bothered me because of my old ears?
clio09
3,360 posts
 
In most cases high end roll off is the symptom. As we age, typically our high frequency hearing regresses anyway. You're not that old though, not that I could tell anyway. Maybe you just find the sound pleasing, for whatever reason, as I did when I used the LSA with an amp with 21k ohm input impedance. Sometimes we take these ratios and such to an Nth degree when in reality maybe it doesn't make as much difference as we think.
almarg's avatar
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almarg
9,670 posts
 
09-28-11: Banquo363
Am I right in believing that non-ideal impedance match between phono stage and LSA results in a attenuation of the high end? Perhaps it hasn't bothered me because of my old ears?
Not necessarily. It depends on how the two impedances vary as a function of frequency. If neither varies significantly over the frequency range, there would be no adverse effects, just a slight gain reduction.

I couldn't find any indications of the output impedance vs. frequency characteristics of your Allnic H-1200, but more often than not the most significant output impedance variation of a tube-type line-level component will be an impedance rise at deep bass frequencies, due to the output coupling capacitor that is commonly used. That would cause deep bass frequencies to be attenuated, assuming the input impedance of the destination component is reasonably flat as a function of frequency.

What will attenuate high frequencies is a combination of high output impedance (at high frequencies) plus high cable capacitance (or, in theory, high input capacitance of the destination component, but that generally doesn't occur in practice, and I assume does not occur with the LSA).

Regards,
-- Al
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