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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
 
Good to hear Dpac996.
In your quest to sample a buffer after it, even though I believe the best buffer is no buffer so long as the impedance boxes are ticked for passive use.
If you want to try an simple good stable at unity gain opamp buffer, the most transparent/dynamic one I have come across in my experiments with I/V stages and buffer stages for cdp's is the AD825, the OPA627 is a tad cleaner but it doesn't have the dynamics of the AD825 and dynamics = rhythm and pace.
Cheers George
dpac996's avatar
dpac996
433 posts
 
I have figured out that the buffered output is a better match in my system. I am amazed, however, at my system performance with this new twist on a buffered volume control. The Lightspeed attenuator coupled with Theta's (Mike Moffat design) implementation of the BUF-03 results in an outstanding linestage. There is an ease and naturalness of presentation that makes listening a real pleasure.
pubul57 OP
3,712 posts
 
You would think the real market for George's attenuator would be in licensing to other manufacturers for use in other preamps and integrateds. Virgin works well for me, but a combo with buffering when needed seems like the next iteration.
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pubul57 OP
3,712 posts
 
I think it is patented, in fact I think George has already nixed one such attempt of using his design commercially without permission - but George could speak to that.
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