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

Showing 7 responses by swampwalker

Ditto. Have not checked in here in a while. Was floored by the bad news. We'd corresponded back and forth but had not yet managed to get to the same show at the same time. Rest in peace, cyber-buddy!
The irony about "simple" designs, with fewer parts, etc, is that it really requires some design chops to execute a great, simple circuit and I suspect it requires a master like Nelson Pass to design some great First Watt and XA.5 amps with such apparent simplicity in lack of complexity.
Or as my fellow Nutmegger Samuel Clemens once wrote:
"I'm sorry that this letter is so long, but I didn't have time to write a shorter one".

Translating this to the post I quoted, it's usually easier to fix a problem by adding a bandaid than it is to go back and rework the design to eliminate the problem.
Of course, if your amp has its inputs in front.... Anybody on this thread have any leads on a monoblock w the inputs in front???? Paul, Ralph, anyone????
How could Photonman not own a Lightspeed???? Seriously, it's a great product. If you don't need source switching, it probably IS the biggest bargain in high end.
George- I own an LSA which I use in a second system and have swapped it in for my Doshi in my big rig and it acquits itself very well. I think it's one of the best values in audio, providing 80% of the performance for 5% of the cost. But you're not doing yourself any favors by posting "reviews" that your customers have sent you. IMO, they have no business in the forums. Buy an ad or put them up on your web site. Just like ads (explicit or implicit) for items for sale are not appropriate. And I believe that Paul (Pubul57) would be disappointed to see you invoke his memory to justify rudeness. Paul was always unfailing polite in any of his web postings. IIRC he felt as I do that your LSA is one of the ultimate value products and hit his sweet spot for price:performance when paired w the RM-10 amp for his Merlins but I don'.t think he would ever have said it was better than ANY active nor would he have approved of your suggesting that he had made disparaging comments about Grannyring, Agear or anyone else. He had more than class than that. Your passion for your product, your technical achievement and your generosity in sharing the design details w the DIY community are quite extraordinary. If others
don't see on things the same way you do, that's OK. That's why god invented chocolate AND vanilla.

Really. The LSA speaks for itself to anyone who listen is to it.
Hi Bill- Glad to hear that the surgery on your back and your system both went well. As long as it sounds good it is good! And with your back feeling better, well, I'd say you have made some very good decisions. Best wishes for a fast, full recovery!