2. amps-preamps
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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
fiddler
581 posts
 
Teajay,

Why are you so worked up over how George says what he says. He has every right to voice his opinion whether you think it is arrogant or not. And simply because you don't like his "absolutes", who are you to question his right to post however he wants. Your haranguing of George sounds a lot like an attempt at censorship and censorship is not at all what makes your "home base" thrive.

My OPINION is that you come across just as arrogant as George does at times. If you aren't interested in the Lightspeed, why bother continuing to come into the thread to stir the pot? Just like George, you are free to post however you like, but where's you dog in the fight?
clio09
3,355 posts
 
Finally the truth...
pubul57 OP
3,712 posts
 
Teajay, I know you have owned a very fine TVC passive, as well as the Placette Active (buffer - no gain) - so you certainly were and might still be open to unity gain in a preamp conceptually. Do you (and Grannyring, et. al.) think that the magic provided from your active linestages is a result of gain, or buffering?

Just to show my bias here, I suspect if the active is working better for you it is not about gain, that if your source output is twice or more what your amp's input sensitivity is that gain is simply a non-factor in the quality of sound - as Nelson Pass quoted above suggests - it is just a waste (to paraphrase). I don't know if you agree with this so far. But it does seem that any improvement would come from the buffering effect to match impedances better and control ICs (as Ralph Karsten would suggest if I understand hime correctly, and perhaps A. Salvatore might argue the same) - and then there is the issue of tube beuffering versus solid state.

So gain? Buffering? What is the active doing that makes it work better in your system? I will say that in the case of both George, and Roger Modjeski (RAM Labs/Music Reference)they both felt that adding a buffer would only be a step backwords as they both felt I did not need it (though Roger would build it for me if I insisted) and that no buffer always sounds better than any buffer if you don't need buffering.

Now Roger does not come on these sites to comment, but his argument for passive is pretty much identical to George's, though George also argues his passive mousetrap is better since there are no points of contact between wiper and resistor (always a good thing?). Roger's only comment was about the challenge of maintaining channel to channel balance across frequency which he thought would be difficult - but I think he thought the LDR idea was interesting....
clio09
3,355 posts
 
According to Ralph a line stage has 4 functions:

1) control volume
2) select input
3) add any needed gain
4) control the interconnect cable at its output

The last of these is the critical, as well as, the least understood one in his opinion. Ralph feels a *quality* active linestage will control cable artifacts better than any passive (and IIRC he has indicated in this thread the LSA is the best passive he has heard). From Ralph's design philosophy (true balanced differential, 600 ohm standard) I can see his point and even accept it. He's done the research, it's been substantiated, and it's evident when you hear his components working together. Pretty much why I'm willing to get a buffered version of the MP-3 to match up with my S-30.

However, high-end audio is more about single-ended than balanced (as well as more about mixing components from different manufacturers than matching them) and in a single-ended environment given some of the parameters discussed here and elsewhere regarding impedance matching and cable characteristics, I believe a *quality* passive linestage can competitively match up with a *quality* active linestage. Additionally, in my case the cost differential being such that money saved using a passive has allowed me to improve other areas of my system substantially.

Now as for designers who have spoken on the topic of passives, here is another opinion from Jeffrey Jackson of Experience Music:

http://www.jeffreywjackson.com/preamplifiers.htm
teajay
1,691 posts
 
Dear Fiddler,

You really pulled out of your ass the idea that I even impiled any type of censorship or that George does not have the right to post his opinion on any thread including this one. Just another way of deflecting what I was really addressing his arrogant and condescending attitude towards anyone who does not agree with his viewpoint and using this thread to market his product. I guess I'm arrogant to share my opinion. Please give me one factual bit of information that would support either my attempt at censorship or being disrespectful towards anyone on this thread. If you and Clo09 want to start a Teajay Fan club I'll send both of you an autographed picture for free. Just let me know. Being the arrogant bastard that I am I know you guys would surely want my picture hanging on your wall.
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