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
>> Maybe true to the source should be more about the least coloration added to something that's been colored from the beginning.
...
If I can eliminate one source of coloration from the mix I figure I've taken a step in the right direction (for me anyway).
<< Clio09

You get it.
"If I can eliminate one source of coloration from the mix I figure I've taken a step in the right direction (for me anyway)."

I think that is why things like soundstaging seem to change more than usual from recording to recording with the LSA - it is putting less of a imprint that carries through for every recording. The question becomes does the recording have depth, width, and localization cues - when it does, the LSA sounds like that, when it doesn't the LSA shows that too. The more neutral the system, the greater variation of these types of attributes from recording to recording. I think this was Ken Stevens' (CAT)notion of a preamp having the color of water, for him you should never be able to tell what preamp is in the chain, there should not be a sonic sameness between recordings that the footprint of the preamps sonic signature. No right or wrong here, I think, just a chosen approach to building a system, one that appeals to my sense of things.
I'm having trouble following this debate between Knghifi and George, particularly with respect to the use of the concept of 'source'. Originally, when I read 'source' I thought it just referred to the music as found on the CD or the vinyl record. At other times, the reference appears to be to the source electronics (CD player or TT). On one occasion, George seems to be using ‘source’ to refer to both, “What comes after the source can only be corrupted by more electronics, it cannot fix a "bad" cdp dac or cd.”

Clio suggests yet another sense of ‘source’ when he writes,

Maybe true to the source should be more about the least coloration added to something that's been colored from the beginning. By that I mean we need to take into account what the recording engineer adds to the mix before it gets stamped as a disc or a piece of vinyl and can be played on our sources. Lets even go further, the instruments played by the musicians add color to a recording whether by composition (ex. wood) or effects (ex. tube guitar amps or feedback).

This is ‘source’ in a truer sense, in my opinion, because it takes us back to the original musical activity that was recorded. [One could ‘go back’ even further and speak of source in the sense of the musical composition, e.g. the musicians are only interpreting the source. And if you’re a certain kind of philosopher, the ultimate sense of source might be the music as it exists independently of even the ‘composer’, e.g. one could argue that Mahler only discovered the 9th symphony, he didn’t invent it] Nevertheless, I think we should leave these latter senses out of the discussion because no manner of electronics design is ever going to get us back to them.

The specific understanding of ‘source’ matters because it influences our stand on several different theses. We can all agree presumably that playback should be guided by the norm of neutrality (compare: all action should be guided by the good; all belief should be guided by the truth). And we can say that neutrality is achieved when a suitably situated perceiver (“ideal listener”) can hear the music as it exists on the vinyl or cd. In this sense, the music on the vinyl or cd is the source. Three theses immediately present themselves:

a. There is no such thing as neutrality (compare: there is no such thing as truth, only interpretation or, differently, preference)
b. Neutrality exists but cannot be achieved
c. Neutrality cannot be achieved because of the nature of electronics
d. Neutrality cannot be achieved because of the nature of perception

Knghifi seems to subscribe at least to (c) when he writes, “Every component has a sonic signature. It's not bad or good but just a sonic signature.” George denies (c), at least regarding the LSA, because he claims that it “adds nothing and subtracts nothing.” In addition, George denies (a), and Knghifi’s position on (a) is not clear to me. Could the correct combination of components get us back to the source/neutrality? If Knghifi believes this, then there is yet another disagreement between him and George because George believes that “What comes after the source can only be corrupted by more electronics, it cannot fix a "bad" cdp dac or cd. It can only add corruptions, colourations, distortions and euphonics.”

For my part, I believe that neutrality exists but that it probably cannot be achieved due to the nature of electronics. I believe the LSA achieves partial neutrality in the sense that the signal it receives it leaves more or less unaltered. However, I don’t know of any cartridge or stylus or TT that achieves what the LSA achieves with its own work. Knghifi’s reference to the total system sound is pertinent here because it helps articulate why neutrality is difficult if not impossible to achieve. This isn’t a knock against the LSA. Perhaps we should be speaking in terms of degrees of total neutrality. If so, and if the LSA does what George says it does, that is, leaves the signal as it is, then that explains why many of us like it so much: it gets us closer to where we should be.

Lastly, I want to return to an issue raised by the total system sound perspective. Knghifi has asserted, and others have intimated, that finding the correct combination is important. I’d like to ask, “Important for what reason?”

i. Because, irrespective of questions about neutrality, a certain preferred sound is acquired
ii. Because the correct combination helps us achieve neutrality

Point (i) seems to deny the importance of neutrality as a norm. I started above by saying that we can all agree that it is a norm, but the more I read people’s postings, the less I’m sure about this. This touches upon thesis (d). If you don’t believe in neutrality, is it because of the vagaries of perception? Or what?

Point (ii) suggests an intriguing possibility. Does anyone believe it? George gave us a reason to deny it, but I’m agnostic myself. Why couldn’t a known type of distortion be corrected by another? Don’t people use and buy cables based on this possibility?
Here's my 2c worth, after noticing this thread had recently come back to life.

Most good quality high end cdp's are close to each other in sound quality and don't colour the sound much at all. Except for some tube output ones - they can be all over the shop.

This leave us with the interconnect colourations. So, why throw a $14,000 bandaid at a pair of $100 interconects, wouldn't it be saner to change the interconects?