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
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.
fiddler
581 posts
 
"Seems I am being attacked for no real reason by you."

"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."

Sure sounds like whining to me.

This is a typical Audiogon exchange seen here everyday where owners or designers defend their equipment, legitimate or not. And I don't see anyone being attacked in this thread. The closest thing I see to someone attacking another person is you attacking Georgelofi.

Georgelofi simply asked a legitimate design question relative to synergy with the TRL and you got your panties in a wad. Apparently Georgelofi isn't entitled to question a TRL product or its specs because as we know, the TRL is, ""An utter and complete step beyond anything (you) have heard regardless of price."

Maybe if TRL was more forthcoming on their website with some specs other than a picture and a price, we wouldn't be having this conversation.
clio09
3,360 posts
 
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 think you're reaching on this one Bill. George was curious as to what the load was on the Samson. He couldn't find any specs and it's well known that TRL doesn't publish them. So all he had to go on was his experience.

Here is what George actually said:

One question Knghifi the poweramp TRL Samson you used for the comparison, it's a solid state amp and I have looked everywhere for it's input impedance and nowhere can I find it, as the Lightspeed Attenuator likes to see 47kohms or higher for the poweramp it's feeding. If the TRL is lower than this you have still not heard the Lightspeed at it's best, and heaven forbid it may beat out the VAC Signature if it sees an amp with the input at 47kohms or higher.

Where's the cheerleading there? Where is the dishonest dialogue? Again, he indicated what has been said here and elsewhere about LSA requirements. Had the specs been published and he could of seen them I'm going to assume we wouldn't be having this conversation. He would have known right off the bat that the input impedance requirements were met.

I don't see where Knghifi is being attacked (pretty strong word don't you think). As for you being attacked when reporting your findings IIRC correctly there was a lot of confusion in that dialogue regarding the definition of transparency. Yours being different than what others here including myself interpreted as the meaning. We all stated our opinions and preferences. Personally I found it a pretty interesting dialogue and it made me think about how I listen.

This thread has had a pretty decent life. Sure it dies down but it always comes back. I think it's done a good job of opening up some peoples eyes as to what is possible sound wise for such little investment. As Fiddler indicated there is a fair amount of cheer leading in the forums, take for example the Supratek and Audio Horizons threads. Do you happen to recall these?:

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1142509250&openflup&2&4#2

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1016931418&openusid&zzGrannyring&4&5#Grannyring

These are just the first posts I ran across.

I'm surprised there isn't a "Dude best preamp" thread on here. Maybe there should be. If there was I'm sure we'd see our fair share of cheer leading, as well as a lot more controversy than what we've seen here based on past TRL threads I have read and participated in. Heck it probably would get deleted just like the last TRL thread on the digital forum.
pubul57 OP
3,712 posts
 
Let's just leave it at this. The LSA is pretty good, and "not bad" for the money. Give it a try and decide for yourself if it competes with the $$$$ gear, I think you might find the test interesting and well worth keeping even if you decide it does not better your $$$$ linestage, or, some of you just might sell your $$$$ linestage and spend the money elsewhere, including, possibly, more music:)

Everyone, have a great New Year, I hope is 2011 is better for all of you.
knghifi
1,668 posts
 
I just report what I (and several audiophile friends) hear and didn't felt I was attacked. But I do understand Grannyring point in Georges questioning of the Samson input impedance, which can be construded negatively, after it was confirmed by multiple sources it's well above 47kohm and my personal listening experiences eventhough I don't have golden ears.

3 more points:

1. My MW Transporter has the ability to drive amps directly so it has more than enough gain.
2. Liveline IC between LSA and Samson is 1M.
3. TRL Dude has a tube regulated power supply so it makes no sense for the Samson to have an input impedance below 30kohm.
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