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
I still say it's not a preamp! Any direct comparisons to other real preamps are somewhat misleading. Kudos to the designer/manufacturer for calling it what it is.
Lightspeed Attenuator, Best device for controlling volume in an audio system ever? including "real" preamps?
In regards to comments on the Morisson Elad.

I too read the hype a few years ago and searched long and hard to find one. I then had a custom power supply built to suit our 240 Voltage here in Australia.

I had it in the system for several weeks, constantly A-B'ing against the LS. The best overall description I can give the Elad was it just sounded "duller" in all areas. This was irrespective of cabling lengths or impedance matches/mismatches.

However, I sold it to an aquaintance who still uses it to this day and actually prefers it over my LS, in his system !

As stated elsewhere, the LS is not for all and can be a harsh taskmaster indeed. It will make you "lift your game" and requires your whole system to be in order, to show it's best.

Easily worth the effort - IMHO
In the Lightspeed design taking the switch out of the equation further simplifies an already simple design. The Pot in the Box is also a very simple design, but the Noble pots, as good as Roger feels they are, will impart a sonic signature. Transformers and autoformers are wound with lots of wire. I've been watching the transformer winding process and will be learning to do it myself. All that wire has to have some effect on the sound rendering the TVC or AVC less transparent and neutral (silver or copper windings would also have some effect). I can think of two reasons why TVCs and AVCs are popular. One they are more forgiving of impedance mismatches and two, in the case of transformers, they offer some isolation.

I'm considering building a PITB for the fun of it and to compare against the Lightspeed. Also, many people like the Luminous Axiom passive devices. I'd be curious as to any opinions on these from owners. Come to think of it I've got a pair of EVS attenuators lying around I should throw in the system for the fun of it.
Clio09
but the Noble pots, as good as Roger feels they are, will impart a sonic signature.Clio09

This is what I found, all have a sonic signature because of their very soft wiper contact, this has to be a very soft as not to wear out the resistive track it runs on when you raise the volume up and down. This soft contact behaves like a rectifier (diode) trying to convert some of the AC music signal into DC especially the faster transients and higher frequencies. This is why all pots sound different even switched resistor pots, all are a little different in this wiper pressure/material/ & and mechanics, none are perfect as a soldered resistor would be, which is what basically the Lightpseed Attenuator is.
TVC are better here as they do not have wipers, but their problems lay in the 500mts or so of very thin wire the signal has to pass through, this itself is a mine field of current limiting, capacitance & inductance all of which is harmful to the original source (CD DAC or Phono) signal.
The best sound you will get is to put your (CD DAC or Phono) directly into your power amps with a VERY quite CD track first, this is the most perfect "true to the source" sound you will get, and only the Lightspeed Attenuator is closest pre or passive to mimicking that sound.

Cheers George