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
tompoodie
37 posts
 
Clio9, could you share what those Atma sphere tweaks are?
Also, is anyone aware of a mechanical switching box that would allow one to have, say, 3 rca inputs and one output. That would allow one to have multiple source inputs, and still use the Lightspeed attenuator. The alternative is simply unplugging one source, and plugging in another...how barbarian... but worth it to avoid a line preamp.
georgehifi's avatar
georgehifi
10,312 posts
 
Tompoodie
Also, is anyone aware of a mechanical switching box that would allow one to have, say, 3 rca inputs and one output.

There are many out there here is one. This is the best way as it will still allow you go direct when you want the best out of the Lightspeed.
My prototype has two inputs with the best switch you can get and it is still bettered by every single input production Lightspeed I listen to before shipping out.

http://www.mcmelectronics.com/product/DISTRIBUTED-BY-MCM-INP-3-/50-6170

Cheers George
koestner
673 posts
 
George,

Are you, or could you, consider making a fully balanced version with some sort of remote volume function?
clio09
3,360 posts
 
Clio9, could you share what those Atma sphere tweaks are?
Tompoodie

No. Please contact Ralph directly. The tweaks may not be applicable to you and your system. Only Ralph can tell you that.

As for a switch box, Decware makes a nice one. I just unplug my cables. Guess I'm a barbarian. The price you pay for the best (IMO) sound.

Are you, or could you, consider making a fully balanced version with some sort of remote volume function?
Koestner

LOL. Been down that road with George, except the remote part. It's hard enough matching LDRs for the single ended version let alone what it would take to match them for a balanced version. Not too mention according to George it might not sound as good or be as reliable as the single ended version.

Let's bear in mind that the reason the Lightspeed is so good is its simplicity. Adding inputs, remote, balanced design, etc. just complicates things. George addresses all this in detail on the DIY.com site where he has been gracious enough to share loads of information. If anyone wants a balanced version I mentioned in a previous post on this thread that George (or I if you email me) will send you a schematic. You could build one or have one built. There is a site (forgot the name but I think its mentioned in this thread) where you can get matched LDRs, and possibly a completed board, leaving you with just the hardware to sort out.
koestner
673 posts
 
Since the resistor changes with the amount of light, could I open the case and use a light bulb with a remote dimmer to change the volume?
More to discover