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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
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
georgehifi's avatar
georgehifi
10,312 posts
 
Sorry typo above
"5 different mV settings to get 4 that are equal resistances at 1 2 5 10 & 20mV each."
It should read mA not mV

Cheers George
pubul57 OP
3,712 posts
 
Well, the warm weather has come back to Baltimore, so I took out the Atma-sphere MP3/M60 combo (the best I have heard for the Merlin VSMs) and took out the diminutive Music Reference RM10 MKII (light loaded at 27 watts) and the LSA (so small I had trouble finding it ;)). After several months of listening to one of the finest pairs of pre/amp combos at any price, I can only say this, if you speakers are 89db or higher and don't have wild impedance swings (bad for tubes) I think the MR/LSA combo, at a list price of under $2,500 for both is going to give you sound about as good as it gets. You may be tempted, as an audiophile, to insist on spending 10-20K, or more, for your electronics, and of course I have, but the truth is you don't have to. This combo, with the beauty of EL84 tubes, is going to give you sound that is just about as good as it gets, and to top it all off, they are both indestructible as far as I can tell. Do yourself a favor, stop thinking you need 100 watt tubes amps, and large complicated preamps. Now if you have already done that, than you have the money to try this combo and decide for yourself. For me it is the making a SOTA sound on a beer budget, without compromise.
clio09
3,360 posts
 
Funny, I just pulled the RM-10 MkII out of the closet as well. Such big sound from a small piece of gear. A wonderful synergy too with the LSA. It just gets out of the way and lets the amp do its business.
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