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 use a SB Touch digital out to DAC only for internet radio. I could not believe the improvement after replacing the Touch noisy SPS with a LPS. It appears SPS is adding noise even when not in used. Removing it from the system was one of the best inexpensive tweaks.
I'll post my impressions.

First impressions, and then after a few days of play.
Just wanted to say that I'm still happy with my Lightspeed Attenuator. I plan on never getting rid of mine, and in fact, I'll probably buy another one when I build a second rig.

Thanks again George, you're a trooper to still be active in this thread as I'm sure you've answered every question 3 times! If you quit, I'm sure no one would blame you and I'm sure you'd still be selling Lightspeed Attenuators, as they kind of sell themselves.

Incredible product, ridiculously low priced for what you get!
I guess I'll go first. I received the TeraDak power supply today and played with it for 3 hours or so. The first thing to note is that it works as it should. That's more than can be said for the battery I ordered for the LSA when I first got it years ago. That died within minutes.

The unit comes well packed and looks decent enough. Mine came with 3 wood isolation cones and corresponding supporting wood disks. That was either a mistake or a surprise New Year's gift, because I didn't order them. The cones are quite nice so I stuck them on the unit with some blu-tac. It doesn't come with a power cord so I used one that was just ready to hand.

The second thing to note is the retina destroying red indicator light on the front panel. Damn that thing is bright! That thing needs to be covered up. I left the unit powered up but unused for about an hour as I acclimated to the sound of the LSA with wallwart. When I switched over there seemed to be a significant attenuation of volume. I checked with my trusty radio shack db meter and, as far as it can detect, there was no change. Puzzled, I continued to a/b the two power supplies for the next two hours. Looking back, I believe the sense of volume attenuation was due to the decrease in distortions caused by the wallwart. The teradak smoothed out distorted peaks and thus gave the appearance of being softer in volume. It gave me the desire to turn up the volume. Another thing I noted was an increase in transparency. This was evidenced by how much more clearly enunciated were the words of songs. There were possibly other changes as well, e.g. in dynamics and soundstaging, but I didn't have a chance to fully explore those.

Obviously, a couple of hours is insufficient to draw any definite conclusions. Nevertheless, I'd be surprised if someone said they couldn't hear the difference between the teradak and the wallwart. Unlike with reports involving battery supply/wallwart comparisons, the differences noted here are not at all subtle. And I am not in any way a power cord guy. My few forays into after market power cords have ended in disappointment.

For $60 this thing is a no brainer in my book, if only to mess around with a new toy. I believe it improves on the already stellar sound I was getting, so it is for me better than just a new toy. YMMV.

Needless to say, I have no affiliation with the Teradak's maker.
Hi Banquo363, that's great to hear, but I am a bit shocked at the amount of difference you heard. Are you in the US or Canada?
Is it possible the 110v wall wart you have is a SMP (switchmode)?
As I cannot supply 110v wall warts to the US.
I only supply my own linear wall warts to 220-240v countries.
If your 110v wall wart is a smp (switch mode) then this would explain the big difference you heard, as they are very dirty, even though regulated, and can radiate their crap right through the system, even via the air.

Cheers George