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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
musicmuskrat23's avatar
musicmuskrat23
1 posts
 
Hi George,

i am listening your lightspeed attenuator now for three weeks.
The first impression was not very good, but after burning in the lightspeed attenuator works better and better. I think there is a minimum burn in time of 50 hours.
Now there are very transparent mids, deep bass, and fine highs.
The space between instruments and voices is very good.
Definately the best preamp i ever owned.
My system is:
Denon DP 75 with Jelco SA 750E and EMT XSD 15
in a handcrafted very heavy plinth
Acoustech PH 1 phonopre
Goldnote Koala Anniversary tube CD Player
Valvet A 1r2 mono amplifier
Dipol speaker with active dipol bass from Packhifi Berlin, the very best speakers i have ever heard.
It's connected with synergistic research tesla cable.
I am very satisfied, maybe there is a friend, who will buy a second attenuator from you.
Best regards
Joachim
georgehifi's avatar
georgehifi
10,312 posts
 

Hi Musicmuskrat23, thanks for your very kind words.
As for burn in I do believe that the Cadmium Sulphide component of the LDR does take a while to "form" after it's not been powered for long periods of time.
I've seen this on the scope from new, but it's only a short duration. But in HiFi as you know anything is possible.

As my ESL speakers are big ML's, I've measured them with an ESL volt meter, and they are fully charged within 5- 10mins to 5kv, but I swear they sound better after an hour, at which time they are still at 5kv.

Cheers George
whart's avatar
whart
2,993 posts
 
tes test test
roymail
10 posts
 
Hi George,
Since receiving the Lightspeed attenuator last week, I've had the pleasure of using it as part of my single source wireless audio system. Just as a reminder, I'm streaming Spotify Premium audio from my laptop using Airfoil for Windows to an Apple Airport Express connected (wireless connection) to the Lightspeed attenuator, then into my amplifer. I used two different amps, a TPA3116 with an Aston power supply, and also a Luxman R114 (amp section only). The amps have an input impedance of 30k (TPA3116) and 47k (Luxman). These different impedance values present no noticeable audible sonic effect at all.

The Lightspeed attentuator is the first passive volume control that adds real dynamics to the mix regardless of the listening volume. It allows for lower volume listening without losing any part of the sonic picture or dynamics. With other passives, I had to turn up the volume attempting to hear all the detail in the music. Using the Lightspeed that is not necessary. This is a new experience for me, to enjoy the music with all it's fullness and beauty while listening at lower volumes. Awesome!

Regarding clarity, resolution, detail, transparency, it's all there in spades! Best I ever heard without a doubt. Even low frequency notes are resolved in a way I hadn't noticed or heard previously on familiar recordings.

One other feature of the Lightspeed VC that I really like is that the control knob has plenty of adjustment to set the volume just right. In other words, unlike many active preamps, the Lightspeed increases or decreases the volume in a subtle manner, a little at a time. And, it allows the user to utilize the full travel of the volume control.

The Lightspeed VC is the perfect addition to my simple single source system. At my age, and with my simple audio system, I do not foresee ever needing another volume control. Thanks, George, for providing such a wonderful audio product at an affordable price. It's amazing!
georgehifi's avatar
georgehifi
10,312 posts
 

The Lightspeed attentuator is the first passive volume control that adds real dynamics to the mix regardless of the listening volume.

I've had this said many times back to me by Lightspeed Attenuator owners, and asked by them why this is so.
These are my beliefs. Try to stay with me with my explanation below.

In normal high or low quality volume pots, the source's easily corrupted low level signal has to travel through it. And there is a dimple point contact between the wiper and the resistive track it wipes on.
This is very light point of contact on purpose so not to wear out the delicate resistive resistance track. The source's signal has to travel through this point of contact.

These pots are also made from two dissimilar materials, the wiper usually being brass and the track another material. This can be the source of a "Diode Effect"
And when turned up or down this effect can change the amount of "Diode Effect" and influence on the sound, the lower the listening level the higher impedance part of the track, the more "Diode Effect"??

Imagine the link below as a normal audio volume pot high or low quality.
The "screw" being the source input of a pot, the "whisker" being the pots wiper, and the "rusty razor" blade being the resistive track of a pot

http://www.electronicstheory.com/COURSES/projnkits/projDiode.htm

As Roymail and other owners have pointed out to me, the Lightspeed doesn't loose it's sonic picture, dynamic ability, and fullness regardless of the level being listened to.
To me this is because there are NO light contact points at all in a Lightspeed Attenuator, everything is hard wired and soldered.

Also Dartzeel with their $25k NHB-18NS preamp maybe also must think this, as they have used the Lightspeed volume in it, they call it a "Pleasure Control"

BTW: Roymail thanks for the great review!

Happy listening
Cheers George
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