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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
 
10-11-10: Agear
CDPs generally suck when driving amps directly due to a lack of current (not merely a function of output voltage as some have suggested above in this thread). Current, from my limited understanding, is needed to reproduce in particular lower frequency information. Agear

CDP's (not tube output ones) have lower output impedances and therefore and higher driving current ability into power amps than 99.9% of tube preamps.

Cheers George
pubul57 OP
3,712 posts
 
George, that is what I thought but being an E.E. ingnoramus I did not feel comfortable making that claim, or the my EMM Labs CDP seems to have a pretty well built power supply. I think that whatever it is that some prefer with active linestages (even when impedance matching, current, and gain is not a problem), and they have every right to feel that way, it is not something actually in the recording, but a distortion that might "feel" truer to some, but cannot be truer to the source in fact.

The argument of passive versus active may be as unwinnable (and it does not have to be "won") as the old SS/tubes argument, what I feel pretty comfortable saying however, is that in a well matched source, cable, amp environment, the LSA is the best passive volume control I have had in my system after trying all the major alternatives. In a different system setup than what I have, I might prefer a unity gain with buffer, or an active tube linestage.
clio09
3,360 posts
 
Well said George and especially Paul.

Hopefully the LSA will make an appearance this Friday or Saturday at RMAF. I would love to set it up in a few different systems while I'm there.
pubul57 OP
3,712 posts
 
I wish I were going to RMAF this year, that steak house was great and the Audiogon party at the Mexican restaurant was a hoot - have fun!
grannyring's avatar
grannyring
6,519 posts
 
No, it is the recording my preamp has more fidelity to, not distortion etc... I have heard Van Morrison live on many an occasion and the weight and heft of his voice is missing on the LSA compared to the active.

Sorry, but them there are the simple facts in my system.
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