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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
clio09
3,360 posts
 
The DAC has enough output voltage, and if the output impedance is less the 200 ohms you should be fine. My understanding is that it uses a tube output stage so I'm guessing that the output impedance is higher the 200 ohms, but you'll have to verify that.

As far as the TRL OTL's I've spoken to Paul about them but we didn't talk about specs. I suspect the input impedance should be high enough, that being greater than 47k ohms. I find the sensitivity of the amp to be less of a factor. I run the LSA with my S-30 and even though the amps sensitivity is nearly 3V, the LSA does just fine. Still, you should check on that spec.

Being that the LSA has just a single input you should consider the fact that if you have more than one source you're going to have to get used to swapping cables around. Doesn't bother me at all, but I suspect I'm in the vast minority on that. Then again, your TV/BR may not have the proper specs to match up with the LSA anyway. I'll let George address that one.
georgehifi's avatar
georgehifi
10,312 posts
 
Excuse my ignorance, what is meant by TV/BR? TV? but what is BR?
Any source is compatible, so long as it has over 1v out and is lower than 200ohms output impedance.
I have customers with tuners, Dat-tape, reel to reel, cassette and phono stages all used very successfully with the Lightspeed. There should be no reason a TV should not work either, and the earphone outlet could be used also as they are generally low output impedance to drive headphones.
Cheers George
clio09
3,360 posts
 
BR = Blue Ray.
georgehifi's avatar
georgehifi
10,312 posts
 
Ha!!! Blu-ray, you guys love abbreviating things, like LSA for my Lightspeed Attenuator, every time I see LSA mentioned on the web I hope it my product being talked about but 50% of the time it's the LSA speakers. Down here in Australia we do the opposite, and lengthen things, for instance for "wife" it becomes the "trouble and strife"
Anyway back to the sources compatibility, anything is, compatible dvd, BR, ect: phono stages are very worth trying from reports of the LP playing customers I have as phono stages benefit greatly by having a Lightspeed controlling the volume, be careful though some old tube phono stages are too high in output impedance, but then two of the customers have a tube stage that's 2kohm (2000ohm) output impedance and they said to me it's the best they've ever heard their vinyl played, and have ditched their mega dollar preamps.
Cheers George
pubul57 OP
3,712 posts
 
George, roughly what is the tolerance for channel to channel matching, and do you feel that is stable for the useable life of the product?
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