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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
3,360 posts
 
What I understood from George's comments based on his experience was that bipolar designed circuits would not typically have a 100k input impedance and many examples of this design had less than the 47k ohm the LSA requires, in some cases significantly less.

Could it be possible to design a circuit using bipolar transistors that is an exception? Obviously the answer is yes assuming the Samson specs are accurate and I have no reason to believe they are not. I'm basically accepting the designers statements at face value since I don't have the amp myself to take a measurement and lack the necessary experience to refute the claim.

In somewhat of an analogy Roger Modjeski wrote an application for an EL-84 circuit that gets at least twice as much power than others have been able to achieve using the standard circuits published in books. So perhaps this is a new twist on a standard design that allows for a higher than normal input impedance. The only people who can actually tell us are the designer or an owner who has the ability take a proper measurement. Personally its hardly worth the trouble.
fiddler
581 posts
 
Quit your whining. Virtually every thread on Audiogon displays this type of "mine is the best because I own it or I built it" post. Why are you so surprised it happened here.

And the posters in this thread have certainly not been cheerleading the LSA any more than you do TRL products. Does this sound familiar, "TRL ST-225 is the best I have owned. No remote however. It absolutely opened up my music collection like no other high end piece of gear I have ever heard. An utter and complete step beyond anything I have heard regardless of price.

I cannot imagine a better sounding set-up. If so, I want it yesterday!"

And this is just one example.
georgehifi's avatar
georgehifi
10,312 posts
 
Who cried "foul"??? All that was questioned was the the load the Lightspeed Attenuator was seeing into the Samson amp to see if it was working at it's optimum, it is you have tured it into something else.

Cheers George
grannyring's avatar
grannyring
6,517 posts
 
Fiddler, I am not whining at all but making a reasonable point. Sorry you are upset. I am not talking about cheerleading at all and want to hear it when someone has found a great piece.

Seems I am being attacked for no real reason by you. That is to bad, as I simply tried to broaden the scope of discussion by pointing a real tendency to "blow off" comments by some based on the general "bad synergy" catch all. This has not been done by all, but by some. It happened to me and Knghifi when we reported our findings in an open and honest manner.

Both our amps were well over 47k and we used a digital source with plenty of output.

My comments have nothing to do with "mine is best" but points out that some have had good synergy and while liking the Lspeed preferred their current preamp.

You can quote my gear praises all day if you like, but you are off point.

I am talking about honest dialogue here and not about product cheerleading. I would have not posted a thing if the builder did not quickly run to the catch all "bad synergy" comment on Knghifi's Samson amp. According to the amp's spec it is indeed good synergy. I simply want accurate and productive discussion that is open to the facts.

I have stated and state again that the Lspeed is a wonderful buy and a great value. I am not trying to hurt it's reputation or upset owners. Seems my point is clear and I am sorry if you misunderstand.
agear
1,362 posts
 
Two months ago, a friend loaned me his LSA as I was curious and wanted to do a shootout between it and the TRL Dude. Like King, I also own the Samson monoblocks.

The critical "Heather test' was performed (blindfolded wife + one glass of wine as a bribe). It is an even more sensitive test than the beloved Bolero test George referenced. Result: Dude. It was not close. I live in Charlotte, NC, which gets toasty during the summer, but the Dude does not heat up the room that much, so I am not in need of a cool running SS pre. I am glad King and Pubul57 can use the LSA in that capacity.

I guess the real question now is the validity of George's statements above about bipolar resistors and the Samsons. From what Paul Weitzel has told me in the past, the Samsons possess higher impedance and gain than most amps and thus should be perfect for evaluation of a passive unit like the LSA.
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