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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
 
Like I have always said Tony, it will work and sound ok with no damaging side effects.
But the source should be at least 3 x or more lower output impedance than the the load. I imagine then it could have sounded even better.
Now can you imagine what Teajay heard when he listened to the Lightspeed into a 15k load and drew his conclusions?

Cheers George
pubul57 OP
3,712 posts
 
George, I'm not sure that Teajay's "LSA test" was with his own system, it might have be a group of audiophiles getting together, comparing notes - obviously testing the LSA with Pass gear would be far from optimal, like testing a 3 watt SET with a pair of Maggies - no way to fairly assess either the amp or speakers in that situation.

Anthony, it will be interested to hear what Tsuda has to say, something does not seem right.
clio09
3,360 posts
 
Just ran into this thread. Seems another LDR attenuator has been making the rounds as a DIY kit. There is a balanced version available as well. Not sure technology wise what the differences are with the LSA, but thought some of you here might be curious to read about it anyway:

http://www.diyaudio.com/forums/vendors-bazaar/176847-warpspeed-optocoupler-volume-control.html
grannyring's avatar
grannyring
6,519 posts
 
I just received the October issue of Stereophile. Please read Sam's Space as I swear I could have written that piece! He does a nice job explaining why some like actives in his well written and balanced article on preamps. Nice job Sam!

I could not possibly agree more or have said it more simply than Sam. He is not saying one is better, but just gives another perspective to consider. Yes, ALL devices (active & passive preamps) have a sound and they all impact a total system's sound. Pick the one that suites your fancy and sounds most like music to you. Great piece IMHO.
pubul57 OP
3,712 posts
 
I agree with Sam, when you need gain or have an impedance mismatch and long cables you need an active line stage, and I imagine when you need an active it is pretty obvious when comparing it to a passive. I agree that ultimately one must choose what fits their fancy, especially since it is "reproduction" we are talking about. When you need an active, a passive will not do. What we cannot do without is a great preamp, in whatever form is most suitable to our source/amp/cabling.
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