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.
So, my first post on this here forum after much lurking in the shadows...

I had the chance recently to try the LDR attenuator at home courtesy of
a friend here in the UK and I have to say it's one of the nicest surprises I've had in 30+ years of messing about with high-end hifi. Well done George!

I've ordered one.

Finally, my definitive review on the Lightspeed Attenuator, by George Stantscheff. Here's what happened...

I was happily playing with a pair of Magnepan 0.6 QRSE speakers, powered by a Portal Panache integrated (and a Velodyne DD12 sub to complement the Maggies). Sweet system, killer bass and I could listen to music for hours without falling asleep or being annoyed.

One day I got the opportunity to trade the Magnepan/Velodyne combo for a pair of fully restored Apogee Duetta Reference speakers (all new ribbons by Graz)... a no-brainer of course. Although the Panache is one powerful integrated, the Duettas really benefit from more power. I did like the amp a lot(!), so I searched and found a pair of Portal Paladin mono amps. Naturally, this meant I needed a pre-amp because I lost the (passive) pre of the Panache.

First I tried the Placette RVC. Nice and compact, features a remote, single input (RCA), single output (RCA). A bit outdated and cheap cabinet, generic Sony remote, but hey... as long as it sounds good. The Placette really delivers in terms of musicality, but I did not like the bass response. Although Placette and the Stereophile review are correct in stating that it's not lean as with other passives, it lacked the impact of active preamps. So I sold the Placette.

Then I tried the Rothwell Indus SE. Average sized box, sheet metal and acrylic front (mine was black, silver controls). Multiple inputs (RCA), dual outputs (RCA), tape monitor, etc. The very unique thing about the Rothwell is the dual volume control. By dividing the steps into a coarse and fine stepped attenuator, it offers a lot of steps combined, while having only two resistors in the signal path at all times, keeping the maximum output impedence a lot lower than most others. No remote though, which was tough after the Placette. However, the Rothwell Indus SE beat the Placette in every area. More tansparent, more separation and the bass had a bit more impact. I liked it so much that I had already developed an add-on module, with Arduino Uno controller, remote, stepper motors and display to stack on top of the Indus SE to be able to remote control it while keeping interferences out of the box. Too bad that personal schedule and the loss of Rothwell's main tech guy threw lead me to sell the unit.

In Nov. 2013 I was picking up where I left, and after a couple of reviews I decided to try a passive pre-amp called Lightspeed by a fellow named George Stantscheff. I was curious about the performance after reading up on the design, and after a brief and very kind conversation about impedances, cable lenghts and what not, I ordered the dual mono model from George directly. Three weeks later it arrived, carefully packed. The box itself is very compact but heavy enough not to be dragged off a shelf by cabling. Single input (RCA), single output (RCA). No remote, but I was simply too curious. A non-switching DC power adapter is included to operate the LEDs which determine the output through the LDRs.

My trusty source for all of these years has been a Pink Triangle Litaural player, so the only difference was the Lightspeed. I hooked it up, set the volume per channel by ear and sat down for a quick listen... which turned into an hour... which turned into hours. What struck me is that I didn't try to analyze the sound at all. Sometimes you read that a 'veil was lifted' or something of that nature, but that's usually just a combination of factors like improved high frequency response, less distortion and the fact that you introduced a new component in your system in the first place, while you anxiously tell your brain to pay extra attention and focus on the details. So I'm not stating that 'a veil was lifted', I was just listening to music and completely struck by the natural level of detail, instrument sounds and dynamics of the music.

As with all new stuff, how exiting it may be at first, you get used to everything in the end. So I decided not to post a review immediately, but wait a couple of months before doing so. In the meantime, I scored a second pair of Portal Paladin amps. After about 6 months of using the Lightspeed, I hooked up the second pair using Cardas F-type RCA splitters. I can tell all purists right away, using splitters is inaudible, period. The real difference was more power, which really opened up the Apogees and controlled them like never before. The bass was even better (due to the second pair of amps) but that also showed mme the Lightspeed wasn't a factor in this, not at all.

However, due to expanding the setup, I felt I should take another 6 months before finally writing this review. So, here we are... hence the opening paragraph: my definitive review on the Lightspeed.

I would go as far as stating that the Lightspeed ended my search for another preamp, even ending my search for other components. It completed my setup and quite contrary to the previous statement that you get used to everything in the end, I am still amazed by the Lightspeed every time I listen to music. It simply isn't there. It shows the strenghts and weaknesses of the source material, the source component, and has no effect whatsoever on the signal going into the 4 power amps. Not doing anything to the signal is the greatest achievement in my book, and this thing is a world champion at it. It fused my components to a coherent system and I've enjoyed it from day one, never ever feeling the urge to 'upgrade'.

Music never ever felt so good, the imaging and soundstaging is superb, tonally everything is what it should be, every instrument is spot on, I can't say anything about pace and such, because all of that is up to the source and power amps in the end. The Lightspeed is perfect in every way, while being as absent as it can be.

Now for the ONLY, very very personal side notes. First of all, for those of you who are absolute control freaks, one word of advise: get the stereo version. I ordered the dual mono version and it can really, seriously mess with your head. It took me a year to just set the volume per channel by ear and be happy with it without wondering if it was 0.5 dB off between channels. If it sounds right, it is right!

Secondly, I would really really like to have a remote control on it, because of the type of volume control it is. Turn it up to 9 o'clock and your older CDs will sound great, throw in a post-1995 CD and your cat will get scare of its life (you may too). Doing every adjustment between CDs will be less stressful when you could remember a good absolute value on a display, easily set with a remote (without loosing the possibility of separate volume control per channel). I personally volunteer to design the volume control add-on box which main task should be NOT to interfere with the beautiful and mindblowing performance of the Lightspeed itself...

Thanks George, for giving us the Lightspeed!

Features: 6/10, Performance: 10/10, Value for money: 10/10

Final setup:

- Apogee Duetta Reference loudspeakers
- Portal Audio Paladin mono power amplifier (2 pairs)
- George Stantscheff Lightspeed Attenuator
- Pink Triangle Litaural CD player
- Grover Huffman ZX 8ft speaker cable (bass)
- Grover Huffman ZX+ 8ft speaker cable (mid/high)
- Grover Huffman ZX+ 1m RCA interconnects (3 pairs)
- Cardas F-type splitters (1 pair)
Nice review. I especially appreciate your decision to wait a while before pronouncing judgement. Too many people jump the gun with conclusions in this hobby.

Has anyone here tried the passives from Tortuga Audio? I haven't, but they use LDR technology and offer multiple inputs, remote control, balanced options and some other features. I'm curious how they compare sonically.

So I thought I'd post a bit of feedback now that the LSA has had a couple of weeks of play to settle up.

My regular attenuator is a Townshend Allegri passive which retails for very many times what the LSA costs. Retail price is not a reliable indicator of performance as we know: just setting the scene.

I have to say that the LSA is simply astonishing. It is fluid, extended at the frequency extremes and has a lightning fast attack at the leading edge of notes, then a detailed and realistic decay. Instruments exist in their own space and are distinct from others. There's a quiet confidence to the sound, with a dark background seemingly devoid of interference/noise. No grain, silken and natural.

That's the thing: this really plays music rather than sounding like "good hifi". Music sounds real and involving.

The LSA seems equally happy with Hans Zimmers massive layering and soundstage as it is with Marcus Millers dynamic bass guitar, Army of Mushrooms's bonkers electronica or Jan Garbareks soprano sax. It all works.

In short: Well done George! Overall, the LSA bests the Townshend in my system.

'...Has anyone here tried the passives from Tortuga Audio?...'

I had an LSA and now have a Tortuga Audio. The only reason I switched was that I found a used Tortuga that had two outputs and of course the remote with volume and balance control is very handy.
Sound wise, I`d be hard pressed to choose one over the other.