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
AB Systems was off for the Chinese New Year which ended a few weeks ago I beleive. Just before that, on January 10, I ordered the TeraDak U9VA for use with my LSA. It arrived within a few days from China, kind of surprising how fast. Very happy.

There was no need to specify the voltage for the U9VA, it came PnP for the LSA; all I needed was to use my own PC.
This model doesn't have an adjustable output voltage. Nevertheless, it's not necessary when using with the LSA. I am supremely happy with my purchase and highly recommend AB Systems.

About three days ago I sent AB Systems an e-mail about and have not heard back. I hope all is well.

~Tom in Sacramento
I also see that Output Voltage is "adjust" between 0.25V and 9V. Is output voltage adjusted by user...or preset by the vendor to user requirement?

There's nothing to adjust on mine--at least not on the exterior.

I bought mine from their bay store, but I see that they have nothing presently for sale...hmmmm.
I came across this thread in my mission quest to find linear, regulated power supplies. I have a non-LSA application and need 5V @ 3A output with a 120V input. However the specs listed on the site seemed to be just what I need since it indicated
"DC output: 0.25V-9V adjust (Default DC 9V 1A)"
though I am not sure what the maximum amperage is if not the 1A indicated.

Need to wait and see if my "proof of life" inquiry gets a response. ;-)

IF anyone knows of another linear, regulated alternative to the TeraDak other than the pricey and overkill KECES D-116, I would love hear about them.
Drubin, I wouldn't use the Pardo;the 12V/2A will fry it. The LSA takes 1A max I beleive. I'm not an expert, maybe others with more knowledge will chime in here...