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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

Showing 6 responses by darkmoebius

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.
darkmoebius
900 posts
 
09-09-10: Clio09
I have used the Lightspeed with both MC and MM cartridges. No issues whatsoever. With MC I use 68db gain on my phono stage and the Lightspeed is at about 2 o'clock or so on the dial. With MM I use 42db gain and the Lightspeed is at 11 o'clock or so on the dial.
What was the output of your low MC's? (maybe I screwed something up, I'm a vinyl newbie)

The 0.25mV 103D into my phono pre+active stepup's 64dB gain yielded 0.4V, that just didn't cut it into either of my amps, especially the 1.5V monoblocks.

I suppose other important factors would be size of room, sensitivity of speakers, listening distance from speakers, musical complexity, and desired listening volume.
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.
darkmoebius
900 posts
 
They have a term for what this has become....... "Circle-jerk"
darkmoebius
900 posts
 
09-09-10: Georgelofi
Strange? I have lots of Lightspeed Attenuator customers that use vinyl with low output moving coil cartriges, all they have is a good phono-stage like the Tom Evans and then Lightspeed Attenuator directly into their poweramps, and they are at 12o'clock on the Lightspeed for good loud level, with plenty headroom left in reserve, they say it the best they have ever heard their vinyl sound.
It just so happened that my active stepup(+22dB) amp and phono preamp(+42dB) were just a little short when it came to overall gain using my Denon 103-D(0.25mV) and Grado "The Statement" (0.5mV). It was possible to use the Grado with my PX-25, but but not with my 300B monoblock amps(1.5v) and other amps.

Obviously, there are other phono preamps with more gain, but I really liked the performance of mine(+TVC) with higher output carts, at the price I paid for them.
darkmoebius
900 posts
 
09-09-10: Clio09
Dynavector 20XL low output version rated 0.25mV. However, mine was going into amps whose sensitivity was rated 1V and 0.7V respectively.
The extra +4dB gain that you have over my phono leads to ~37% more output. That could be the difference between barely acceptable and good performance. But, now you've got me thinking that I may have jumped to a flawed conclusion and I should have played around with more IC's. Sadly, I sold the Graham Slee Era phono & EXP stepup, it's possible I didn't need to.

The upside of this may be that I have no reason not to try the Lightspeed in the near future. Especially at it's price.

maybe I'm mistaking you for someone else...I've been to that pictured location in San Pedro listed on your system page (I think you've moved since then) and bought one of your two Scheu turntables at the time. Having two of those tables, me thinks you're probably not a vinyl newbie, but hey, when it comes to vinyl set-up we all make mistakes.
Ha! Good memory, that's me. I moved out of that house 3 years ago, and have slowly been selling off the system for "the next big thing"(which still hasn't happened). I still have the Cain & Cain speakers and the Scheu w/ 80mm platter, though. I'm in a much, much, smaller apt right now, but want to get a vinyl and really good headphone system going in the next few months to hold me over until I move again.

I guess I should be saying "Full Lightspeed ahead!"
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