2. amps-preamps
  3. 1276356977

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
clio09
3,355 posts
 
If you need something that can drive long interconnects and provide impedance matching there are still active buffers like The Truth, Pass B1, and Burson Audio that will get you there while still providing a high level of neutrality.

The long interconnect advantage is really only valid for active preamps that are true balanced designs. Most audiophiles are running single ended systems and while you might be able to stretch the interconnect a meter or two further, I suspect it's the color of the month they're really looking for. On top of this perceived notion that 10db or so of gain is going to make a real difference in dynamics, slam, and 3-D presentation.
pubul57 OP
3,712 posts
 
"perceived notion" - you know, I think part of that must come from the fact you might have to turn the volume control to 2-3 position at times and there seems to be an intuitive conclusion that there is something lacking, drive if you will, that makes it necessary to go to such "extremes", where with an active it can be hard to go beyond 10:00 on the dial, making you feel you have to have tight reins on the surging power lurking within the preamp beast. Perhaps Nelson Pass touch upon this psychological dimension to the perception of power and drive.
clio09
3,355 posts
 
What I find amusing are these threads where people complain they can't get past 9 o'clock on their volume control. They're looking for a way to get more control over the range. In some cases they end up buying Rothwell attenuators to get a 10db reduction that gets them to 10 o'clock instead.

Several posts above I quoted what Nelson Pass had to say about the psychological dimension to the perception of power and drive. Seems he figured it all out a while ago.
Ag insider logo xs@2x
banquo363
371 posts
 
I've never turned my volume past 12, and most often have it at 10. Both vinyl and CD. What is responsible for having to turn it to 2-3? My ear drums would rupture at those levels.
pubul57 OP
3,712 posts
 
sensitivity of amp, sensitivity of speakers, size of room, how loud you like it, and hearing acuity. now, if i switch the cd players gain to 4v, i never go above 12.
More to discover