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
The LSA will sound much more like the Placette than either will sound like a tube preamp. You should stick what you enjoy most. Are you using the Placette with an SS or tube amp? I could not, would not[?] use a passive with an SS amp for a variety of reasons, but that's me.
Yes, I have a solid state Luxman amp.
The combination of my tube preamp and the Luxman is extraordinary. So I think you are right. thanks.
You might enjoy your Placetter, and passives in general, much more with a tube amp - or what you are doing with the excellent Luxman amps - use a tube preamp that matches well with the lower impedances of SS amps. I love the sound of tubes, and I need them somewhere, but not in my pre if I have them in the amp. Always interesting discussions on where the tubes make the more important and significant difference = preamps or amps - I suspect the sonic stamp is stronger when the tubes are in an amp -- but that is a debate.
With the Luxman amp you might want to try the Dodd Audio tube buffer. It gets quite a bit of praise from those who have tried it. In fact, there are some really nice solid state buffers out there as well, namely the Pass B1 and the Horn Shoppe Truth (which uses a photo optocoupler). Buffers are similar to passives in that they generally will not add gain to the signal path, but they also eliminate impedance mismatches.
Thanks again Pubul. I actually have 2 amps, an Edge NL12.1 and the Luxman (both solid state), and the tube preamps I tried with these really makes a superb sound, w/o the heat & tube maintenance issues of powered tube amps.
Of course, this works better with speakers that aren't ruthlessly revealing or tipped up (but I don't favor these speakers anyway).

But really, the tube preamp makes all the difference with these amps, especially with some good NOS tubes, with life, palpability, gorgeous texture and tonality and lack of fatigue with detail simultaneously. The solid state and passive preamps were just flatter and not as engaging.