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
Thanks Pubul57 and Clio09. My amp has input impedence of 47 KOhms and input sensitivity of 1.27 Volts rms, my source has a output impedence of 120 ohms and output voltage of 2 Volts. It is close to what you and George S. recommend so it should work. If not it might be time for some newer items, mine is over 20yrs old. It sounds like this could be a great reviewers tool? Thanks for the input.
Hi Anthony. I meant the battery and connector you provided links to. Would it be a plug&play purchased as is? In terms of the negative/positive pin issue?
The battery is plug and play. The link to the connectors show several. The one I indicated is the one you want. It is center pin positive. Most are default that way, but you need to be certain as reversing the polarity on yours with a center pin negative connector will damage it. The information for the one I referenced says it is "inside positive" which means center pin positive. Buy this one with the battery and all is plug and play.
I've contacted RH at "tas", and raved about the Lightspeed. I have had both SoundLab electrostatics, and Magnepan 20.1's, and I am after purity, with no added colorations. I have owned several amps of different circuit designs and preamps, tube and transistor, active and passive. The Lightspeed in the audio chain is non-existent, everything that's on the recording is there, nothing more, nothing less ... perfect. I mentioned to Mr. Harley that when I read Jonathan Valin saying he misses the "bloom" and "spaciousness" of tubes, with ANY piece of equipment, I cringe. If I want to hear phase manipulation or harmonic distortion, etc., increasing the stage depth and image width, it ought to be on the recording, not being created by my components. I see this elsewhere in criticisms of passives, and amplification in general. If someone wants to alter what the recordists have compromised, then, an equalizer is in order. The real music is At The Venue, anyway. It's pretty disturbing, as well, to think what monitoring speakers or headphones recording engineers may be relying upon to record in analogue OR digital. As an insane lover of this hobby, and an ex-musician in love with music, I know that the sound I'm getting also relies on the careful system matching of associated equipment (which is equalization of a sort, in itself, but those pieces have inherent sounds of their own, unlike this attenuator) ... interconnects, amp circuitry, speaker transducers, "wall-power" purity, transport or turntable mechanisms, server quality, ad-infinitum. The Lightspeed may have it's own system-matching limitations, but it's absolute transparency is exactly what I want any component to emulate. No sound of it's own. If I can't be at the performance, I'd like the source recording to be good enough to allow me to enjoy the music. I hope the Lightspeed gets into homes where it is understood and appreciated. This thing is a treat, absolutely incredible, and the price makes it affordable for just about anyone.