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
"That to me is an indication of the LSA's transparency and faithfulness to the source, and a lack of transparency in The Dude. By transparency I am referring to lack or presence of coloration"

Let me further explain as I think my statement needs more context. I feel it is a matter of taste and not accuracy at all. The LSA plays the instruments more up front and forward - and I mean all of them! The instruments play on the same plane at the front of the speaker. Some may like this. However, to others it is a lack of 3D perspective or depth.

The Dude plays music with greater depth and not all the instruments play on the same forward plane. Some are more set back and not as "up front" on the performance stage. The performance has more perspective and depth. If the recording offers only a forward perspective for all the players, then the Dude reveals that. If the recording is more layered, then the Dude gives that deeper layered presentation.

I found the LSA made my favorite recordings all share that same forwardness for all the instruments. In other words, every recording began to take on the same personality with all the music coming from a plane at the front of the speaker. The whole of the music seemed to be traded off or lost as the vocals and instruments all competed for attention at the front of the stage.

When I attend a symphony or other great sounding live music events I hear instruments positioned differently on the stage with many of them at differing volume and intensity levels. The Dude seems to reflect that reality more. This is exactly what I mean in my statements above. To my ears, in my system, the Dude is every bit as transparent as the LSA, but the Dude seems to possess more fidelity to the space and dimension of the musical experience.

Rather than compare the two which only I can really do based on actual experience, I do find one topic very interesting. Some feel that an active preamp is adding warmth or coloration to obtain a richer sound that is somehow not really in the recording or live musical event. The conclusion given by those is that this richer sound experience is not as accurate or true to the recorded source. This can certainly be true of some active tube units, but not all.

In my experience live music delivers the whole of the instrument. Listen to a grand piano, cello, violin etc… or entire symphony in a great sounding venue and you will hear the rumble, resonance and totality of that instrument. You will hear the orchestra swell in full and rich momentum with a solid deep foundation underlying the whole musical event. Is that added? Is that coloration? I don’t think so. That is what I hear with the Dude. This is what I find missing with the LSA in comparison to the Dude. For me this is critical to reproduce in my home music system. Again, for me alone this is important and it may not be to others. Is a passive missing this part of the music? Is it missing what was intended to be there? Is it actually playing what is recorded and the recording does not sound like the live event? I suppose the last point is possible, but my desire is to hear instruments as they actually sound in a natural setting.
I am not sure a passive is by some mathematical or physical fact the best way to achieve live sound in our homes. Let’s face it; all gear and wire in our systems are reproducing or passing along electrical signals no matter the set-up; Active or passive, tube or SS, horn or ESL, simple or complex and on and on it goes. I don’t think that a passive or active unit is ALWAYS the definitive best means to hearing the wholeness of a musical event – not missing depth, bass foundation, warmth, dynamics, crashing of a cymbal etc…. I cannot accept a sweeping statement that passive units are the best means to live music recreated in our homes. They may be in a particular system to one person’s ears, but that’s about as far as we can take it.
Ok, have it Agoners!
"found the LSA made my favorite recordings all share that same forwardness for all the instruments. In other words, every recording began to take on the same personality with all the music coming from a plane at the front of the speaker. The whole of the music seemed to be traded off or lost as the vocals and instruments all competed for attention at the front of the stage."

That is a very telling statement. I have audiophile friends who believe any pre-amp is a bad pre-amp and should not be in the chain. I fall into active camp. I would be interested to hear how staging and dimensionality is an artifact from a technical standpoint.

I too will be getting an opportunity to hear the LSA and compare it to my TRL Dude. That should be fun. More importantly, I will involve my non-audiophile, musician wife in a blinded listening test between the two and will report on her findings rather than mine.

Tony, you referenced owning a TRL pre-amp. That was Paul's prototype of a battery-powered, solid state pre right? Not a Dude. Out of curiosity, did you ever hear the LSA side to side with that entity? Are you speaking from sonic memory?
The LSA plays the instruments more up front and forward - and I mean all of them! The instruments play on the same plane at the front of the speaker. Some may like this. However, to others it is a lack of 3D perspective or depth.

Bill, was this true of every recording or was it recording dependent? I do find with the LSA in my system it exposes the recordings for what they are. Meaning some have a more 3-D sound stage than others. Some are also more immediate in their presentation than others. However, I can't recall one where all instruments are in a flat plane at the front of the speaker. What specific recordings were you listening to?

If the recording offers only a forward perspective for all the players, then the Dude reveals that. If the recording is more layered, then the Dude gives that deeper layered presentation.

Exactly how it should be with any preamp, active or passive.
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That was Paul's prototype of a battery-powered, solid state pre right? Not a Dude. Out of curiosity, did you ever hear the LSA side to side with that entity? Are you speaking from sonic memory?

It was the Pre-1.5 battery powered preamp and no, I never compared it with the LSA. My comment was a blanket comment on all the active preamps that I have heard since I have been exposed to what well designed passive preamps can do in ones system. To me they are all additive (some more so than others), not necessarily in a bad way, as I do enjoy listening to some active preamps. Again, it's my opinion and anyone can feel free to agree or disagree. Perhaps the Dude is different and maybe some day I'll get to hear it for myself and come to my own conclusion. After all I lent my LSA to Bill so he could do exactly that.