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
clio09
3,355 posts
 
There is something to be said for those that have a conviction and stick by it. I have a lot of respect for what George did with the LSA because he has determined what he feels a preamp should accomplish, and while I agree that his way is no more right or wrong than anyone else, he has developed a product based on his conviction regardless of the fact he could have probably made more money developing active linestages had he chosen to go down that path.

Its like Ralph Karsten's approach and his conviction about using output transformers in amp circuits. He is in the minority among his peers (even though his research and papers do a great job explaining why his approach may be the better one), but he keeps plugging away at it when IMO it probably would have been easier for him to just design a circuit with output transformers and call it a day.

Lightspeed ahead...
grannyring's avatar
grannyring
6,471 posts
 
Tube test complete - no ringing or any bad noises at all. Listened to Van and enjoyed it lots!

I have rolled quite a few 6sn7's in my active preamp over the past two years and have never had a microphonic tube issue as an fyi.

Knghifi, funny stuff.
teajay
1,691 posts
 
Hi Clio09, I too have great respect for Ralph Karsten's designs and his passion for what makes the most sense to him sonicly and design wise.

However, I have no awareness historically that he ever "pushed" his design/product on an Audiogon thread like it seems to me that George is doing now on this one. Please I'm not referring to the information to help members understand his design or optimize its performance, but it seems to me that he really believes that his piece is the "BEST" there can be in linestage.

Your other remark that George, "proably could have made more money developing an active linestage", but chose not to because of his conviction to this design is not only pure conjuncture on your part, but kinda silly that he rather make less money then more from a business sense.His use of the LED design instead of transformers or resistors is quite interesting, but does not put him, in my opinion, in the patheon of designers like Ralph Karsten, Nelson Pass, or Masataka Tsuda.

So, I still believe that the way this piece is being "marketed" on this thread or how George comes across in his "conviction" that his linestage is the "BEST" regarding his design is quite different then anything Ralph Karsten has ever done on any Audiogon forum.
pubul57 OP
3,712 posts
 
I think Terry is a very gifted listener and reviewer with exposure to some of the finest equipment in the world and have nothing but respect for his observations and conclusions about his views on equipment, but though we have owned similar equipment at different times, I think we lean towards a different kind of sound and we might not come to the same conclusions - though I have no doubt I would love his system. He might be right that part of my enthusiasm is in part what the LSA does for the $$$, though I would have no problem buying a more expensive line stage if I wanted to, but ultimately I think it is simply that the LSA works really well in my system and after quite of bit of A/B I felt it offered just as much musical pleasure as my tube linestage, which up to that point was my favorite after several years of listening to various preamps, a line stage with Terry also heard but wasn't exactly his cup of tea.

Still, I do the "best" concept really makes no sense, it makes no sense universally, independent of system context, not does it make sense to any particular listener. But it sure does make sense to try an LSA to see it how it works for you and then decide for yourself.

Ralph Karsten and Nelson Pass? You are right, they are at the very top of world class design talent, as is Roger Modjeski in my view, who also is in the passive line stage camp feeling no active line stage would better for use with his RM10 MKII and RM9 SE amps. Now, while Roger sells a $135 Pot-in-a-Box with a very high quality Noble pot, I think George has simply built a better mousetrap by avoiding a physical connection to change resistor values.

I think there is more debate about active versus passage than between the SS/tube divide in that even within the very same listener one might find ambivalence of conviction over which approach is best over time. I've made that journey several times, the allure of tubes is always there, but at least for me, the Music Reference amps have never sounded better than through the LSA.
clio09
3,355 posts
 
Please I'm not referring to the information to help members understand his design or optimize its performance, but it seems to me that he really believes that his piece is the "BEST" there can be in linestage.
So, I still believe that the way this piece is being "marketed" on this thread or how George comes across in his "conviction" that his linestage is the "BEST" regarding his design is quite different then anything Ralph Karsten has ever done on any Audiogon forum.
Why shouldn't he believe its the best? That's one of the things I like about George (a bit cocky for a designer, kind of reminds me of me in fact). You don't think Ralph feels the same way about his OTL designs? He might be more politically correct (in some peoples views) about how he goes about it, but he often refers to his white papers here to back up his work. Some people consider that a marketing ploy, but I don't blame him one bit for displaying his research and expertise. There's also a little thing going on over AA where he posted a review of one of his amps. Some people have been critical of that, but I take no exception to it.

I don't see where George is forcing his product on anyone here. Does he come on a little strong sometimes with his convictions, sure, but I don't care. As a consumer I get to make choices. This thread has been going on for a while. If something were truly wrong I'd have to think the moderators would put an end to it.
Your other remark that George, "proably could have made more money developing an active linestage", but chose not to because of his conviction to this design is not only pure conjuncture on your part, but kinda silly that he rather make less money then more from a business sense.
Yep, it's conjuncture. However, I get the feeling from reading stuff and dealing with George directly that he being retired had a successful enough run in his career that at this point he'd rather be surfing than working any harder than he chooses to. It's a hobby and something fun for him to do. I can appreciate someone who can make these types of lifestyle decisions when others are slaves to their work.
His use of the LED design instead of transformers or resistors is quite interesting, but does not put him, in my opinion, in the patheon of designers like Ralph Karsten, Nelson Pass, or Masataka Tsuda.
I think Nelson Pass paid George one of the highest compliments when he went public on the DIYAudio thread with his own variation of George's LDR design. Enough said.

I know two of the three designers you mentioned personally and respect them enough that I use their equipment. I consider Masataka Tsuda a friend and one of the most gracious men I have ever met in my life. I'll be working with him again at the upcoming CES/THE SHOW in Las Vegas. So with that in mind I will say that design principles and preferences aside, as well as differences in personality, I think George and Masa are more similar than they are different. Both use some very unique concepts in their designs that should be heard by more people.
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