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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
georgehifi's avatar
georgehifi
10,312 posts
 
Audiolabyrinth hi.
All the gain 2.5v/5v switch is doing is changing the feedback resistor on the output buffer to another value to give 5v instead of 2.5 on the same output buffer.
As far as being concerned that you have 5v out feeding into 3.5v in, this is quite acceptable, as if you had an active preamp in the mix you would have far more than that, as some are capable of giving out up to 20v or more out.
So as you can see it is not out of the ordinary to have more out than what's can go in, just means you have a bit of headroom, just be judicious with the volume control.
And like I said if when on the 5v setting you are below 2/3 of full volume then "Bit Stripping" can become an issue. Then you can get a Lightspeed have the 5v full up and the Lightspeed will be at or around mid 12o'clock position for normal listening with more available if needed. Or you can leave the Lightspeed at say 2o'clock and be able to use the remote volume on the Ayon to raise and lower the volume within the top 1/3 of full up, this way you will not be "Bit Stripping"

Cheers George
audiolabyrinth's avatar
audiolabyrinth
4,555 posts
 
Thankyou Georgelofi, I know what you mean now, you are saying if I use The Ayon 2s on 5 volts out-put, and use the volume control, I would never turn it up to 5 volts, most likly the amp would be driven to full signal when the volume pushes the signal to 3.5 volts!, most likly 1 o'clock on the volume control?,, cheers!
photonman
96 posts
 
Just received mine and have been listening for two nights now and loving every minute of it.

This little box really makes me think that I will never again need to spend bank on a pre, and as such my $3k Bryston is now sitting under my bed collecting dust and soon to be on the for sale block.

Worst case scenario, the Bryston has nothing sonically over the LSA except source switching, which I do not need. The LSA is much more transparent in my system as I am hearing instruments and voices that I never knew existed in some passages, very revealing and detailed.

But the first thing I did after hooking up the LSA, was to turn on my system and with no source playing I put my ear to my tweeters and with a big smile on my face, I heard absolutely NOTHING, no "ocean" white noise that I heard with my Bryston with volume at zero position.
I am guessing that is a good thing but I am only an amateur at this audiophile stuff.

I hate to speak in cliches, but I am really enjoying rediscovering my cd collection. But Of course, each particular recording has a different effect from the LSA. Particularly, live and unplugged music sounds more live and bad recordings sound more bad, a side effect. So your source component is now in the spotlight as to the quality of the signal reaching the amp. Now I am rethinking whether I should upgrade my source, cdp or go digital. Isn't it ironic says Alanis.

I am using a 3 ft set of Bryston IC's (Canare and Neutrik) which are 21 pf/ft into the LSA and a 2 ft set of Blue Jean IC's which are 13 pf/ft out of the LSA to amp.

Another nice side effect, I have one less 17" component box and its outboard power supply, less cables and wires and my rack actually looks organized and clean.

So to summarize, a great sonic value and a truly novel product from a pretty cool guy to do business with from 7.5K miles away.

I am very happy with this purchase and by far my best and most dramatic change to my system.
devilboy
1,176 posts
 
George, I purchased that amp I was thinking about. I tried going amp-direct and controlling volume via PureMusic. The new amp's input impedance is 51K. Due to the amp's .75V sensitivity and 35db gain, most of my listening was 40% or less on PureMusic's volume bar. This resulted in a "swooshing" hiss coming from the speakers which is clearly audible from my listening seat 9 feet away and obviously unacceptable. My previous amp was an integrated so now I need a preamp which brings me back to you. As I said before, I'm a former LSA owner and sold it when I went to the integrated.

I've been looking around for low capacitance rca's on the cheap (for now), to run from the LSA to my amp. I've narrowed it down to Mogami, Blue Jeans, and something else which escapes me now. You said you use Mogami. May I ask which? Studio Reference (or something like that). Also, do you know the capacitance of your Mogamis?
clio09
3,354 posts
 
I recommended Mogami which is what I use. I bought mine here from:

http://app.audiogon.com/listings/interconnects-mogami-rca-1-meter-studio-standard-interconnect-2013-06-27-cables-80015.

You could also try some pro gear stores. Mogami Studio Gold Neglex Quad would be one of the brands to look for.
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