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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
finn
2 posts
 
Hello all, I purchased one of these units (second hand) recently and have been surprised at how much of an improvement the Lightspeed appears to be over all my previous preamps. I have owned some well regarded solid state and valve preamps but for the last few years have been moving into passives. I like the quietness and lack of an electronic signature that they bring. A Silk transformer TVC was followed by a Slagleformer module based pre which I thought was about as good as it could get in terms of naturalness and detail with no loss of dynamics.
Well the lightspeed has pushed out the boundaries considerably. It transmits even more low level detail which seems to expand and flesh out the soundstage. High frequencies are very extended. Tonal colour is enriched and there is more space around voices and instruments. I have not noticed any loss of dynamics or bass which was a strong point of the Slagleformers. Only downside apart from its very basic nature is that my system has a lot of gain so I dont get far off the bottom of the volume control travel at normal levels.
It is a remarkable unit even ignoring the modest price and I scratch my head at the increase in signal transmitted by, as I understand it , the removal of one less than direct connection(the volume control). Should we therefore be soldering our speaker wires to the amps and speakers etc.? Or is this a different issue.
Either way I am very glad I made this purchase.
Regards, Andrew
shakeydeal
979 posts
 
"Only downside apart from its very basic nature is that my system has a lot of gain so I dont get far off the bottom of the volume control travel at normal levels."

I have a question regarding this statement. How can the gain in the Slagleformers be any different than the Lightspeed since they are both passive devices?

I ask this question because I own a Sonic Euphoria PLC and recently made some system changes that has me running at the absoulte extremes on the attenuator. I don't really want to move back into an active preamp because I haven't heard one under 10K that can beat a good passive.

Any thoughts on what the Lightspeed is doing differently?

Shakey
Ag insider logo xs@2x
drubin
3,265 posts
 
Some transformer passives (maybe autoformers too) have gain, usually up to +6dB.
shakeydeal
979 posts
 
That's what I thought. So how does an LDR have more gain than a TVC?

Shakey
georgehifi's avatar
georgehifi
10,312 posts
 
The Lightspeed can never go to complete zero volume (there is always a whisper at min) and in rare very high gain systems such as Fins the volume will be down around 9 or 8 o'clock low for normal listening level, and this will give the impression of more "gain" than a passive that can go to complete zero level.


As "Fin" (Andrew) contacted me about this last week, he gave his system parameters to me. And as you can see below he has a s**t load of gain, with effecient speakers.

They are:
source >2.5v out
power amp <1v in.
As you can see he needs only 1 volt in to for his amp to give it's 100w full power.
And he has more than 2.5v from the source.
And because of this the Lightspeed is down low for normal listening.

Cheers George

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