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
Hi, Audiolabyrinth, tell him to come over here and read this.
I had a quick read of that thread, and there are those that like to be on the preamp merry-go-round, spending lots of money and are addicted to it.

They say that their preamps aren't coloured. But keep changing them for "different sounding ones" (odd I thought they were uncoloured).

I have yet to hear them use the statements like "straight wire with gain" or "true to the sound of the source" as these statements are describing a preamp the is truly transparent, dynamic, uncoloured and invisable to the sound of the source.

Cheers George
Have been reading with interest the comments about the TeraDak and keces DC-116 power supplies and am encouraged that users are happy with the TeraDak given its considerably lower cost.

Is AB Systems (source of the TeraDak) still in business? I have written emails to the Contact@ listed but have not received any responses over the past several weeks. As expected, I am reluctant to order anything blindly.

I understand that Input Voltage must be specified.
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?

Also would like to know what the DC connector barrel dimensions are...5.5mm/2.1mm or other?

Anybody have any experience with their other products, e.g., power cords?

Thanks!
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.