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
My system if a fi2A3, an Abbas DAC, and Klipsch Belle speakers so it seemed ideal for this type of attenuator.  I was expecting it to be fairly neutral since not much is being added but I was stunned by how much improved the clarity of my system was.  The quiet spaces in between the sounds are unbelievable.  I am very happy with this new addition.  
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Glad you enjoy it so much Jeff, that is a very interesting system, low power purest, you need the efficiency of the Belle’s for those amps.
Can you give some info or links on the dac and amp/s as I’ve never come across these before, I take it the amps are SET 2a3’s at a couple of watts each channel?

I quickly couldn’t find much except this made by a Don Garber
http://www.6moons.com/audioreviews/jj2a3/hero_fi2.jpg

I had a 3w Softone SET 2A3 from Japan (no longer made) he makes his own R-core transformers, amps ugly as sin but so cheap, This 3w amp drove a pair of monstrous Goldmund Apologue effortlessly.
http://softone.a.la9.jp/english/

http://www.milliondollarstereos.com/pix100k/goldmund_apologue.jpg


Cheers George
Crazy looking speakers.  The Belles came first and the amp followed.  About 3w is about right and I listen with the Lightspeed at about 1/3 volume.  Very efficient.  The DAC is handmade with the following as some particulars. Very interesting though.

 DAC 2.0SE features:

1.Tube DEM clock (E180F, EAA91)
2.CS8414 SPDIF receiver 24/96
3.Shunt voltage regulators based on the germanuim transistors. The scheme has been improved and has a superior thermal stability.
4. Vintage and modern audio components are used:allen bradley,philips,telefunken,
Capacitors:Black Gate (2pc FK series,1pc PK series),panasonic pureism,Audio note standard (2pc) and Audio Note Kaisei(3pc) 220mfX160v,470mfx25v
5.Board covered with gold and a special varnish for best sound 
6.Stranded wires composed of vintage copper wires taken from klangfilm, telefunken, siemens sound equipment
7. I/U convertor based on the special gold plated low noise vintage transistor. Because of this fact, an excellent reproduction of quiet sounds, at -60.-80db level
8. PIO output capacitors HYDRA from 60th 
9. Shortest signal path, the tube output stage with the low output impedance (5687,EZ80).
10.NOS mode(non oversampling)
11.Genuine TDA1541R1 philips factory
12.Siemens film capacitors in the DEM cells
13.Spdif receiver voltage stabilizer based on unique powerful vintage transistor with a semiconductor crystal on a thin gold basis in the copper case.
14.Separate power transformers for digital and analog sections. Separate transformer for DEM clock.
15.Telefunken choke from 30th in the 5687 power supply.
 

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Genuine TDA1541R1
Best way of reproducing pcm redbook cd, with R2R Mutibit converters. Man after my own heart.


This intrigues me, as I'm right into zero feedback I/V stages for current output dacs/. Any more info on this, circuit perhaps
I/V converter based on the special gold plated low noise vintage transistor

Cheers George