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 4 responses by roymail

Can someone explain the advantage of leaving the LSA turned on 24/7 with the knob at 12:00? I recall reading somewhere that this is what George recommends. It may have something to do with the longevity of the octocouplers.
I may have used the wrong word when I said, octocoupler instead of LDR. My apologies to George.
George, I very much appreciate your answer to my questions. I hope that your explanations also provide help to others.
Hi George,
Since receiving the Lightspeed attenuator last week, I've had the pleasure of using it as part of my single source wireless audio system. Just as a reminder, I'm streaming Spotify Premium audio from my laptop using Airfoil for Windows to an Apple Airport Express connected (wireless connection) to the Lightspeed attenuator, then into my amplifer. I used two different amps, a TPA3116 with an Aston power supply, and also a Luxman R114 (amp section only). The amps have an input impedance of 30k (TPA3116) and 47k (Luxman). These different impedance values present no noticeable audible sonic effect at all.

The Lightspeed attentuator is the first passive volume control that adds real dynamics to the mix regardless of the listening volume. It allows for lower volume listening without losing any part of the sonic picture or dynamics. With other passives, I had to turn up the volume attempting to hear all the detail in the music. Using the Lightspeed that is not necessary. This is a new experience for me, to enjoy the music with all it's fullness and beauty while listening at lower volumes. Awesome!

Regarding clarity, resolution, detail, transparency, it's all there in spades! Best I ever heard without a doubt. Even low frequency notes are resolved in a way I hadn't noticed or heard previously on familiar recordings.

One other feature of the Lightspeed VC that I really like is that the control knob has plenty of adjustment to set the volume just right. In other words, unlike many active preamps, the Lightspeed increases or decreases the volume in a subtle manner, a little at a time. And, it allows the user to utilize the full travel of the volume control.

The Lightspeed VC is the perfect addition to my simple single source system. At my age, and with my simple audio system, I do not foresee ever needing another volume control. Thanks, George, for providing such a wonderful audio product at an affordable price. It's amazing!