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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
wilsynet's avatar
wilsynet
264 posts
 
I decided to take Pubul57's lead. Using the Lightspeed Attenuator with the Music Reference RM-10 MkII. Sources are the db Audio Labs Tranquility SE DAC or the Ray Samuels Nighthawk phono stage.

I don't miss having an active preamp at all.

The sources have 50-60 ohm output impedance, and the amplifier has 100Kohms input impedance. I think with the right components and appropriate input and output impedances you won't miss an active preamp either.
pubul57 OP
3,712 posts
 
Wilsynet, I'm glad you gave it a try. By the way, Clio9 is also using the LSA with the RM10MKII. Not sure if this is the reason why, but one reason I felt the compulsion to try a passive was the Roger Modjeski (Music Reference)told me to use a passive, that no active could be better; though he was willing to build me a more traditional tube-buffered with or without gain. Well, you know Roger can buiild anything, and he loves selling tubes, yet this fella who knows a thing or two about audio insisted to go with a passive. Then I read Arthur Salvatore's comments on passive versus active. Well, I had to go about testing the concept and have had Placette, Goldpoint, BENT TVC and AVC, and Roger's Pot-in-a-Box - they all sounded excellent, these were not gradations of crap to great, they were all at least very good, and at the end of that path I came to the LSA which was the best of the lot IMHO and I'll say that in my system with ideal[?] impedance matches and ICs the LSA is the best passive preamp I have heard, and I suspect if your system well suited toward the passive approach the LSA will give you SOTA sound quality for $450 which is a good thing to know, especially if finance are an issue, combined with the RM10MKII I think that is just about as good as it gets IF 35 watts is enough power for your speakers, room, listening volume.
clio09
3,353 posts
 
Wilsynet, glad you were able to put together this combination. It is incredibly good for the money. I have about $1500 invested in my LSA and RM-10 MkII. That's tough to beat for SOTA sound.

I've been listening to the LSA with battery power supply for a while now. I would suggest to anyone that owns one to give it a try. The parts cost is less than $75 (here in the US anyway) and it's plug and play. Also, I've been using my LSA with the Atmasphere S-30. Now I'm tempted to break out the RM-10 again.
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clio09
3,353 posts
 
I agree with the assessment, although some tube rolling could change that. Pubul57 might be able to share more on that as I believe he has done some tube swapping with the amp. I use the stock tubes as supplied by Roger and the way Srajan describes it is how I hear it. FWIW and if IIRC, Roger designed the RM-10 using Quad 57 speakers with it for his listening tests. There are some other interesting design characteristics about the amp that fly in the face of typical amp designs and how we audiophiles associate various sound qualities with them.

Tvad, if you're interested in hearing the RM-10 let me know. I'm not using mine at the moment. If possible I'd like to compare the RM-10/LSA combo versus RM-10/VRE-1 combo.
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