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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
augwest's avatar
augwest
43 posts
 
I recently put the Lightspeed up against three active preamps ranging in cost from $2400 to $9000. These are my notes from the comparison with the best of the three preamps.

--
Preamp Shootout performed 5/14/2012

SYSTEM
custom modified Music Hall cd25.2 transport > Audio Aero DAC > (preamp or LSA) > Atma-Sphere M-60 Mk3.1 OTL amps > Merlin VSM MXe w/Master upgrade

[1] Active costing ~20X the LSA
Sounds more natural than the other active preamps, possibly somewhat less expansive / dimensional sound stage. Broad midrange presence, dynamics, and tonal texture are very good. Somewhat subdued at the frequency extremes? Bass goes deep and sounds full but something's not quite right down way there, it sounds a little overly warm and compressed. Full-bodied without sounding lush like the LA-150. Drums have the decent transients and tonal balance. Very musical overall - honest, smooth and well balanced. Tends slightly toward polite and pleasant. Perhaps not the very last word in resolution and imaging but absolutely will not offend the ear.

[2] Lightspeed Attenuator
Consistent with careful research, the LSA seems to be a very good match for my system. Sounds way more natural than active preamp. The imaging is back, the bass is tight and clean, the midrange is pure, textured, and expansive, and the highs are crystal clear and never harsh. There is no background noise, no coloration. Seems to have all of the detail and dynamics, doesn't sound lean (at least at moderate to higher volumes). Tends to sound a little better the less it does (less attenuation = turned up = less effect on the signal).

CONCLUSION
I've sold my active preamp. The LSA has earned its place in my system. I may go for a dual unit to regain control over the balance but it seems about right in my system.
dgarretson
2,601 posts
 
Augwest, are you placing the Merlin BBAM upstream or downstream of LSA?
augwest's avatar
augwest
43 posts
 
Excellent question. I've got the Master BAM upstream of the LSA per Merlin's recommendation when using a preamp, but you have to be cognizant not to overload the LSA. My Audio Aero SE DAC puts out 5.5 Volts (!) so if you boost that by 5dB using the BAM you can end up with pretty huge signal (~12V?). The LSA can't handle that.

Fortunately the AA DAC has vairiable output (actually a complete built-in preamp) so I set it at ~ -20dB and forget it. Of course you need to take into consideration the input sensitivity of your amp(s), i.e. how many Volts Input results in Full Output. But if your source puts out a more conventional voltage of a volt or two you might have no issue whatsoever.

RELEVANT ASIDE: I sometimes wonder if part of the reason that the LSA does works well in my system is because of the robust tube output section of the Audio Aero DAC (100 Ohm output impedance). It may not be perfect but I'm impressed with its resolution and musicality, and it will drive just about anything! I will probably be holding on to it until I decide to ditch my CD's in favor of a server.
clio09
3,360 posts
 
Thanks for the comparison. I have used my LSA with an Atma-Sphere S-30 amp for vinyl playback with great results. Right now though until I get my vinyl rig hooked up again I am running my Resolution Audio Cantata direct into the amp via the balanced outputs and using the internal volume control. It works quite well for my digital needs. Have you tried running the AA direct to the amps?
georgehifi's avatar
georgehifi
10,312 posts
 
Hi Paul (Augwest) I had no idea that was you that gave the glowing review on the Lightspeed Attenuator I sent to California.
As said with a source that could give out 5.5v this the Lightspeed will take but if it goes through the BAMM as well before getting to the Lightspeed this can add a further 5db boost to the bass which takes the 5.5v up to something like 10v before hitting the Lightspeed.
That is why I would try the BAMM after the Lightspeed, or my second choice if the BAMM must go as you have done is to turn down the 5.5v of the source to a volt or two as you have also done.
Good to hear that it still sounds better than all those preamps you put it up against, as I always claim the Lightspeed Attenuator will give the most transparent and dynamic way from lows to highs of controlling the volume from a source to a poweramp, and at the same time being totally honest to the source not adding or subtracting anything. The closest thing one can get to a straight piece of wire with control over the volume.

Cheers George
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