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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
georgehifi's avatar
georgehifi
10,312 posts
 
I use Express 6 MkII interconnect by Eichmann but I don't wire it like they do, I put all reds together and all backs together I found this sounded better and was more electrically logical, the way they had it was strange and sounded that way.
I also like it because it is substantial have 6 solid core individual conductors of about .5mm each 3 red 3 black individually insulated the encased in a blue gel type outer sleeve with no shielding at all, as I have found shielding can increase capacitance/inductance.
Also I like that is pure 99.99%ofc copper, I have never liked silver or silver coated, I find it artificially accentuates the highs, giving a false impression of detail while robbing body from the lower-mids and leaning out the bass.
Then for speaker cable the same Express 6 MkII speaker but its twice as thick probably 1mm conductors
Back to work
Cheers George
grannyring's avatar
grannyring
6,517 posts
 
Scott, you agreed with me actually as I was talking about about the LS and RM10 combo of only 35 watts. The amps you mentioned are more powerful.
tradeontheweb
43 posts
 
Grannyring, thanks for that - I wondered if that was what you meant !

Cheers

Scott
grannyring's avatar
grannyring
6,517 posts
 
Ok, one last question. If I run my CD player right into my amps, won't that damage the amps or speakers? When this is done will my system play at full volume? Half volume? I can't image playing at full volume as I never go past 1/3 or so right now - to loud!

I don't see how this "test" is possible with no volume control on my CD player. I have never tried anything like this so I may not understand.
clio09
3,360 posts
 
Bill -

Go to the Arthur Salvatore site and read the instructions for the test (see link). There are test instructions for LP and CDP. Ravel's Bolero is a good track to use because it has low passages at the start that will not cause damage.

You're right though, loud passages or even an unexpected loud passage might cause damage. With no volume control on the CDP you wouldn't be able to mitigate damage unless you were to hit the pause or stop button very quickly.

If you are still using the TRL Samsom amps IIRC they have an input impedance of around 67k ohm. The sensitivity is just under 1V. Any CDP with 2V or greater output should be able to drive it. The question is will there be enough volume and will you like the sound. Also, perhaps not with the test but if using any passive preamp the output impedance of the CDP will come into play. Typically this should be under 200 ohms, but under 100 ohms is even better.

http://www.high-endaudio.com/RC-Linestages.html
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