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.
Apparently something like this was once used in the Melos preamp years ago, and in the current DarTzeel (something like it).

I finished my last post by saying try it, since it is almost impossible to avoid cliams of overhype when talking about a preamp most have not heard, and lord knows there have been many flavor of the month, buzz pieces that are long forgotten shortly thereafter. So all I can do is recommend you try it if it might fit your system.

I only offer the context of my views, as a previous owner of many passives that left me feeling like those here that have expressed dissapointment with there efforts at using a passive. First of all I have owned almost every passive of the past five years of all the basic desing approaches and always preferred my active tube line stages. As an interesting point two of the folks that like the Lightspeed have also owned Joule preamps which are on the warm, musical, meaty, organic, etc side of the preamp spectrum, so we know that sound, and in that context, the LS does not dissapoint - it is not cold, sterile, lifeless, flat, missing PRAT, etc. Now, I don't know how to address the warmth issue, since two of my favourite preamps are the CAT SL1s and Atma-sphere and they are not known to be "warmth-lover" preamps, so it may be I don't find warmth as seductive as others, though I do love my Joule LA150 Signature Edition which is warmer than the other two.

Yet one cannot predict how each of us might react to this thing, which is why I say you have to try it and decide for yourself, if it was $5,000 I would want alot more evidence and listening sessions, but for $500 it is within reach of most of us in the forum to decide for ourselves without coming to conclusions drawn from sources other than our own ears.

Best preamp ever? I do think that is a silly question, or at least silly to believe such a thing exists, it does not and cannot. But, the Lightspeed is very, very good, and sound like this from a $5-10,000 preamps (the price of my last five tube preamps) would be great, at this price it seems like a must audition, at minimum, for those on a budget with something like a Music Reference RM10 (1k-2k - used/new) and 89/90db or higher sensitivity, flat impedance speakers for a first rate system at an "affordable" price. For those with plenty of $$$ to spend, at this price it is simply worth trying for yourself and draw your own conclusions.

Even if it does sound as great as I (and others that have heard it/ owned it) am saying, it still will not be the preamp for everyone, since it is VERY limited as a source selector, and does require a source, short (2m) ICs, and amps that can work with a passive - not all can. Just as I would not make claims about 4 watt SET amps sound like from listening to them on a pair of B&W 802s or Thiel 3.6s - I exaggerate to make a point.

If you live near Baltimore, come over for a listening session and compare it with my Joule and Atma-sphere setups and tell me what you think, easy enough to compare.


So this was the 'passive' preamp you started using. If not for this thread, folks will dismiss the LS as a poor mans preamp and miss a great opportunity to discover its musical attributes.

Thanks Pubul57 for exposing it to all of us.
George, why is it that I can hear music still playing with the volume all the way counterclockwise?
The Morrison Elad is just a normal active preamp using normal pot and a 50 cent Analog Devices AD797 opamp with no gain.
It has nothing what so ever in similarity to the Lightspeed Attenuator and it has nothing what so ever to do with LDR's or LED's.

Cheers George
Faziod Hi you will hear very low level of music at minimum level as this is the characteristic of ldr's in this design is they can never go to complete darkness or infinite brightness as these are the controlling factors for resistance. Think of it as there is no such thing as infinite brightness or infinite darkness.
Cheers George