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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
vyokyong
23 posts
 
Hi,

I want to update my Light Speed Attenuator passive pre-amp. It is replaced by Coincident statement Line stage active pre-amp(CSLS) (Transformer Volume Attenuator with DHT 101D tube gain stage.) The reason to replace is that low gain album record can be played not loud enough.

The result of CSLS replacing LSA is that

Pro:
1) Excellent Authority and Dynamics. It is like you change car from 1,600 cc to 3,000 cc turbo charge. Absolutely dynamics and in different world to LSA. It means that dynamic authority gains as same level as any Solid state amp. It makes you feel excite and PRaT. It can play loud peak as 101 dB of any album record (high or low gain). Previously with LSA, it plays as maximum loud of peak 99 dB of high gain record album and peak 87 dB of low gain record album.

Con:
1) All nuances and micro details gone or disappear or high definition sound is gone. LSA or direct connect between source and amp provides or keep all nuances and micro details (high definition sound) which makes you feel realism of LIVE music band playing in your room, very emotional music.

Now it is dilemma for me to choose between Excellent Authority Dynamics of CSLS or Nuance and high definition sound of LSA.

For me, I think that CSLS pre-amp acts as drive stage of source (extension driver stage of source) to enhancing amp to get maximum authority dynamic in bass of speakers. The more gain in IN PUT of Amp. the easier of Amp to drive speakers. But circuit of pre-amp causes signal loss in certain ways, for this case, the nuances and micro details is lost in CSLS.

LSA acts as volume attenuator of Amp. In my case, it is like direct connecting between source and amp so that all signal is kept very well, minimum lost. However if the driver stage of source (Audio Note DAC 3.1) can not provide sufficient gain to AMP (Decware Zen Mystery Amp) then the system is lost in some authority and dynamic in bass.

I will modded CSLS by replacing signal cable wire both in put and out put cable wire to be Deulund Hook up wire 2 version 2 (Pure Ribbon Cable wire)in order to gain nuances and micro details of signal back. Because I observe that signal cable wire used in CSLS is very small normal wire.

I will report back after modded CSLS again.
georgehifi's avatar
georgehifi
4,966 posts
 

Mods can cause more problems in other areas.

The Decaware amp is 100kohm input impedance and it's input sensitivity it only needs 2v for it to give full output.

The Audio Note DAC 3.1 has in standard form 3v output, as you can see this is more than enough.

I believe in an email you sent me that the dac or amp was getting modded?
If so you have lost either gain from the dac's original 3v output, or input sensitivity is now too high (2v to full output originally) on the amp. After these mods.

This is the problem your having with low volume and probably the bass.
If you get these mods rectified to get the gain or sensitivity back, all will be great with plenty of level and bass and you'll keep all the transparency and the micro detail as well.

Cheers George
array1138's avatar
Ag insider logo xs@2x
array1138
64 posts
 
I acquired an Aum passive, one of the original 4 made, and am completely enamored with it. Lack of input selection notwithstanding, it has answered my main issue with most preamps, that being the use of cheap attenuators even in high end amps. My last pre was a Flora EX DT which I still own, and it uses an autoformer that is the best I had heard up until this, even better than my Viva Linea preamp with 300B power supply. The Aum unit is on another level entirely, too bad the maker is leaving the industry. Pure unadulterated transparency with no perceivable signature whatsoever.
My reference is live music, both acoustic performances and amped, since I spent decades managing clubs in NYC.
grannyring's avatar
grannyring
4,637 posts
 
Array1138

I purchased the Aum passive also. The last unit the builder made before getting out. I love the sound as it sounds very much like the Lightspeed, but has remote volume, balance, and other options. It also has two outputs.

I loved the Lightspeed in my current system, but really wanted remote. The unit is much more expensive than the Lightspeed so I really paid for features not sound quality improvement.
vyokyong
23 posts
 
George,

Thanks for your clarify.

It is not false of LSA in authority in bass and dynamic. Before I mod my ZMA amp, I connect my ZMA amp directly with Accuphase DP77 SACD/CD player. The loudness and dynamics is the same as my current set up playing with LSA.

The nuances and micro details are gained after LSA is modded by
1)Changing internal signal wire to be Deulund hook up 2.
2)RCA female jack to be replaced by WBT pure silver female jack.

This is the reason why I have to mod CSL pre-amp with Deulund hook up wire 2 in signal cable wire and WBT pure silver female jack and check the result in sound quality again.

I still encourage that LSA internal signal wire must be replaced by high quality wire like pure silver Deulund hook up wire 2 and WBT pure silver female jack. This mod provides nuances and micro details like changing HDTV to be 4K HDTV or UHDTV.
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