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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
 
I would guess nearly 99% of good quality cdp dacs have an output voltage of 2v (Redbook Standard) or higher and an output impedance of 200ohms or lower.
Amps may have a input impedance of 47K (industry standard) or higher, nearly all tube amps are 100k or higher and an sensitivity of 1v or higher to clip.

So 2v feeding 1v to clip? no preamplfication needed here

200ohm or lower output into 47000ohm? no impedance mismatch here either.

So if a active preamp tube or transistor sounds better in the above "common" situation it is as Paul says giving the owner the tonal quality they want to hear (less bass more bass) you get the picture.
This however a band-aid fix for that system by throwing in a costly preamp to fix a system problem and at the same time missing out on all the transparency dynamics and sweetness that no active pre can give. Would it not be the wise thing to do and fix system imbalance (different interconnects speaker cable and positioning) problem instead of throwing a costly band-aid at it?
Cheers George

grannyring's avatar
grannyring
6,510 posts
 
Like your input George. I would love to try your preamp in my system and compare to my tube preamp. I can't believe I even said this as I am usually 100% against passives based on my experience with these in the past. It's just that several highly respected Agoners seem to think your $450 unit is the real deal giant killer. I have a gaint in my opinion :-)

I have found that my active tube preamp is not a tone control at all. Rather, compared to some nice passives I have tried, like Placette, my music has increased texture, body, stage size, layered holographic presentation and much improved sense of control and utter ease at any volume. All of this while being every bit as transparent.

These attributes have nothing to do with the simple attenuation of bass or treble as a tone control.

I may indeed compare soon. I just can't image a passive unit would match the attributes listed above. If so, your preamp is a wonderful value.
sibelius
256 posts
 
I stand corrected in my Morrison ELAD comments. Thanks for the clarification Georgelofi.

I agree with Pubul57 that for many the straight wire with gain approach is as much a philosophical stand as anything else. I was once one of those folks. Then I became heavily involved with tube amps and preamps and my approach softened. I am aware that a SET tube amp most likely "colors" the sound of most recordings I hear. However,I've made peace with that because I greatly prefer that sound. The issue I have with some "straight wire" proponents is that they can take their stance to the extreme by believing they are recreating live like music conditions via their stereo systems. A quick trip to the symphony is a more than subtle reminder that even the best stereo systems I've heard (Shindo,Audio Note etc..) are nothing more than crude approximations of the real thing.
pubul57 OP
3,712 posts
 
I have never heard a stereo system that sounds like live music, but I have heard stereos that probably sound more the recording - the loss goes from live to recording and it only gets worse from their in terms of sounding live. If you don't go to live acoustic events you might get fooled from time to time, but then I go to a jazz concert and after a few minutes my audiophile mind goes ugghhhhh, and accept that stereo systems are just very enoyable ways to a enjoy music, some better than others, and none close to live.
georgehifi's avatar
georgehifi
10,312 posts
 
Grannyring
I have a gaint in my opinion :-)

Good on you Grannyring you've given me my laugh for the day, I'm just a tech with limited English skills I had to look up "gaint" this is what I found in the Urban Dictionary

gaint: loss of blood to the brain due to overly large erection.

Cheers George
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