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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
darkmoebius
900 posts
 
09-05-10: Clio09
Yes, the sound stage and imaging manipulation that active components and even some cables add to the equation is very evident after listening to a passive preamp in the system. I would agree that the LSA does not have the spatial capabilities of some other active preamps, but I'm fine with that as it does reproduce the music in a truer form.
This is not meant to be to be an attack on the Lightspeed or any other optocoupler, but more a statement about overall component dedication.

Almost all devotees of a particular type of component swear theirs presents a "truer" form of reproduction. I can remember the long, long, threads dedicated to Placette's passive(resistive) units and how they were the ultimate of transparency and everything else was simply distorted. Then came the Transformer Volume Control(TVC) adherents, of which I am one, swearing theirs bested all others and were the truest form of reproduction, soon to be challenged by the Autoformer crowd for that title.

And all of these camps heaping scorn on solid state, tube, and hybrid active preamplification for being "colored", "distorted", etc, etc.

As we all know, it is almost impossible to know which component is "true" and others are additive, or subtractive(except for truly bad components), unless one was present for the actual recording session. As to knowing what is the "true" amount of soundstage width or depth on a myriad of recordings, I think that would be an impossible task.

In reality, any preamplification is probably "truest" if it helps bring the listener a deep emotional connection to their music within the context of that listener's musical preferences and system/room acoustics. Nothing else should matter, in the end.
I'm not sure who it was that said this, it was a reviewer I think, but the point was that the sound stage should not extend beyond the speakers. I think I might agree with this thinking. Depth and height, as well as space between the performers are another matter though.
I would think this would be an oddly distorted "view" of a recorded performance. Most live, and even studio, venues are wider than the average 8 ft that speakers are apart. Recreating a symphony into an 8 foot space would itself seem to be a artifice equal to one that extends beyond the speakers. Neither is being "realistic", but closer to scaled down versions of reality. Much like the difference between watching movies on a 40" or 65" screen.

Having said that, Lightspeed attenuators have fascinated me ever since the first threads started appearing on DIY Audio years ago. I would love to hear one in the near future, but my next system will be (hopefully) all balanced/differential with sources and preamp across the room next to my listening position and the amps/speakers on the other end. This could end up being quite a long distance.
pubul57 OP
3,712 posts
 
I enjoyed reading that, well said, and certainly the issue of what gear will connect the listener to the music is as varied as there are people. As far as soundstaging is concerned, what I do notice with the LSA is that the apparent soundstage seems to change quite a bit from recording to recording, which I suspect is a good sign that the LSA is making and effort to "get out of the way" between source and amp. I also notice, as Clio9 suggested, that instruments do not seem to be oversized or stretched as often occurred with Patricia Barber's piano with some other very fine preamps I have owned. I don't know if you took 10 audiophiles and had them compare the LSA to, let's say, the ARC Ref5, how many would choose one over the other in blind listening, and both can certainly make for an excellent sounding system. But the fact that you could make the comparison tells you just how good the LSA (and other passives - I too have followed a similar path, Placette, K&K, Bent AVC, etc)are in the right system. Will prefer them to fine active preamps? Only listening will tell and I'm sure there will be those that walk out of the room with that Ref5 in tow.
georgehifi's avatar
georgehifi
10,312 posts
 
Darkmoebius
As we all know, it is almost impossible to know which component is "true" and others are additive, or subtractive(except for truly bad components), unless one was present for the actual recording session. As to knowing what is the "true" amount of soundstage width or depth on a myriad of recordings, I think that would be an impossible task.
In reality, any preamplification is probably "truest" if it helps bring the listener a deep emotional connection to their music within the context of that listener's musical preferences and system/room acoustics. Nothing else should matter, in the end. Darkmoebius



Thought I'd chime in on this one being the manufacturer of the "Lightspeed Attenuator".
Hi Darkmoebius, welcome to the discussion, you used the magic word "truest" twice in the above reply. Having not yet heard one for yourself, can I make a suggestion to get the "truest" idea of what pre/amp passive or active is "truthful" to the original recording.
Plug your CD player or dac directly into your poweramp "this will be a perfect impedance match" As you have no volume control, first off play something that is low in level to gauge how loud it will be, doing this you are playing the "truest" form of cd/dac playback you can possibly get. Then slip the Lightspeed or any other pre active or passive back in adjust for the same level, and you will see and hear which one is "truest" to the source.
Cheers George
pubul57 OP
3,712 posts
 
Sounds like the Bolero Test by Arthur Salvatore, which also concludes that if ANY active linestage sounds better than a passive there is an impedance mismatch and the system NEEDS a an active stage. In his view, there is no better connection between a source and amp than the direct connection, and then a passive preamp. Hard to think that all those beautiful tubes in an active tube preamp does not bring beauty and flesh, etc - but it does not seem that any of that is actually in the recording (as the direct connection makes perfectly clear).
darkmoebius
900 posts
 
09-06-10: Georgelofi
Plug your CD player or dac directly into your poweramp "this will be a perfect impedance match" As you have no volume control, first off play something that is low in level to gauge how loud it will be, doing this you are playing the "truest" form of cd/dac playback you can possibly get. Then slip the Lightspeed or any other pre active or passive back in adjust for the same level, and you will see and hear which one is "truest" to the source.
Great point, George!

I actually did this years back with a borrowed Museatex Bidat when comparing my TVC to some active pre's I was considering. The Bidat(300ohms/3.5V RMS max) went directly to an Art Audio PX-25(180k/700mV/6wpc) SET amp driving Cain & Cain IM-Bens(~95dB/8ohm). Obviously, I preferred the passive route.

But, it did pose a problem playing vinyl w/ low output cartridges. I needed the extra gain of an active preamp or a phono pre with a lot more gain.
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