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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
grannyring's avatar
grannyring
6,471 posts
 
Knghifi, I made the exact same point on this thread a while back. I follow what you are saying and it strikes me as the correct way to look at this. This is a very interesting discussion and the main reason I keep looking at this thread.

I tried the Lightspeed and found my active preamp to be more "accurate" to the recording. I am very intrigued with this debate and hope it continues.

I am certain my preamp is not adding distortion or fuzz or any additional "stuff" unless my hearing is not as good as I think :-)

Things like stage depth, dimensionality, micro details, tone etc... make a stereo system sound more like music and more like a wonderful recording. Not sure distortion of any kind would ever help these things? The active delivered this better in my set up.

I bet a passive does this better in some systems. The reason - because the music that emerges from a stereo system is the sum of ALL the parts.
pubul57 OP
3,712 posts
 
I am sure I would like the VAC too:)
pubul57 OP
3,712 posts
 
Reminds me of my conversation with Ken Stevens when I picked of my CAT preamp and amp. Got into a conversation about capacitors and he said when looking for some, the manufacturer asked what flavor of sound he was looking for, he replied "I want the flavor of water". He decided to makes his own capacitors from scratch to pursue the least "damage" to the signal, he felt good recordings should sound good and bad recordings should sound bad - just one of many approaches to line stage design. The LSA seems to be guided by the same principle. What's best? Who knows. But it is nice to have so many choices.
grannyring's avatar
grannyring
6,471 posts
 
Perhaps a good way to look at this topic is as follows;

Let's assume this for starters. Let's compare three systems.
All 3 systems fit the ideal specs needed for a passive like the Lightspeed. We all agree on what sounds the most real and pleases us in terms of sound. Ya, just assume.

System #1
_________

A+B+C = music

System #2
__________

A+B+C+D = music

System #3
_________

A+B+C+D+E+F = music

Ok, since it's the total system that creates the finished sound I think it is accurate to state system 1,2 or 3 may end up sounding more like the recording was meant to.

The more simple system #1 may or may not be the most accurate system. The fact that it is more simple or has fewer parts along the way does not, by definition, mean it delivers a more accurate and pure sound. It may or may not.

System #3 has more parts along the path to the final music. It may have a power conditioner, separate tube buffer, separate autoformer, a subwoofer and on and on the options go. It may or may not be the most accurate system of all.

My point is one component (preamp) cannot, by itself, always give a more accurate TOTAL SYSTEM SOUND. Even under ideal conditions one cannot assume a passive can do this. Same can be said for an active preamp. The signal passes through too much and the speakers alone in a given system can be the point at which one type of preamp is preferred over another (delivers more accurate sound).

It is the sum of the parts. One combination of wire, resistors, caps, transformers (system) will always sound different then another. The combinations are endless with differing outcomes. Some more accurate then others. Fewer parts along the path does not always equal the most accurate. In all cases it will depend on what parts are combined in the total system.
pubul57 OP
3,712 posts
 
This is not regarding the LSA since it is really about as "simple" as can be in terms of parts, etc. The irony about "simple" designs, with fewer parts, etc, is that it really requires some design chops to execute a great, simple circuit and I suspect it requires a master like Nelson Pass to design some great First Watt and XA.5 amps with such apparent simplicity in lack of complexity. For masters of their craft, you often see a less is more approach to design. But ultimately, my preference for simplicity may just be a personal peeve that has increased as I have gotten older. But yes, there are many ways to skin a cat to produce a world class system. What makes the hobby so much fun.
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