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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
 
Sorry typo above "Rather it use the cheaper NSL23SR3" should read "NSL32RS2" no "S" on the end for sorted.
And also thumbs up for the chassis Jylee wish I could incorperate it in my production one and keep the price the same.
Cheers George
mcondon
235 posts
 
I just placed my order for the LSA yesterday, after doing some experimentation first.

My system consists of a PS Audio Perfect Wave DAC/Transport into an Aesthetix Calypso preamp into a VAC Phi 200 tube amp, all connected with balanced cables. My experiment consisted of going "amp direct" from the Perfect Wave DAC into the VAC Phi 200. I found that I could only turn the digital volume control up to 40 out of 100 on the Perfect Wave DAC before the volume got too loud. So I was definitely losing "bits". Still, I preferred the sound of this setup using single-ended RCA cables into the VAC. (Using balanced cables, the amp direct setup had too much upper frequency emphasis...not sure why, but reviewers say that the VAC Phi 200, even though fully balanced, sounds better single-ended than balanced.)

In any case, the LSA will allow me to turn the digital volume on the DAC up to 100 and not lose any "bits". I will report back how the LSA works out once I receive it from George.
pubul57 OP
3,712 posts
 
Great. We await your observations. P.S. if you want remote control, another option would be the Placette RVC, which is mighty fine, though not to level of the LSA IMHO.
jylee
306 posts
 
George, I agree with your assessment. The measurement listed for each optocoupler was god, but could have been much better. Where can I get closer matched quad of NSL32SR2S? Can I get them from you?

The chassis I used was sourced from a shop in asia. The price was well below $100, but the shipping cost was rather hefty. It came out a little over $100 including shipping to California. It's more expensive than the Hammond extruded aluminum chassis commonly used in DIY community, but not by much. Please contact me privately if you would like further information.
georgehifi's avatar
georgehifi
10,312 posts
 
Hi Jylee, I have been asked this too many times to remember, if I do it for one I have to do it for all. Being it's the most expensive and labour intensive part of the Lightspeed Attenuator, sorry but it's only for the production Lightspeeds.
For you to do it to get a quad matched set, you would have to get 20-30 X NSL32SR2S's and match a quad set out of them at 5 different mV settings to get 4 that are equal resistances at 1 2 5 10 & 20mV each. The place you can get them from is here.
http://australia.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=NSL32SR2S
Cheers George
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