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
I'll ask it here, not because it is exactly on point, but the right folks seem to here: Do you think that dual mono attenuators with 2db tapers per step is "fine" enough for using to balance channels? Obviouly that is a non-issue with the LSA becuase it is "infinitely" adjustable.
Hi,
I used to own the very highly regarded First Sound (active) preamp which was dual mono (2 volume controls, 2 input selectors) and it had 2db increments on its volume knob. I found the 2 dB step too large a size to get the volume just right. I much prefer the "infinite" vol settings on the Lightspeed.
That is what I suspect, 2db would not be as useful as one would hope, but I'm speculating, not having tried it.
Yes 2 dB could be problematic in some instances. The 24 step switches with the S&B transformers wired to them were even more problematic since the first few steps were quite large increments, something like 6, 4, 4, and 3 dB steps before tapering off to 2 dB over the next several steps.

My magnetic line amp uses stepped attenuators with 1.5 dB steps all the way through (41 steps in all). I find these to be useful. The continuous adjustment on the LSA works quite well for me too. Even matching both channels is quite easy.
Given the necessary taper for stepped attenuators and the expense of steps, it seems like 1.5db is likely the goal then. Is the MLA shipping yet?