2. amps-preamps
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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 am using Lightspeed Attenuator for 3 weeks already and want to share my impression here.

My system are;

Audio Note DAC 3.1 custom modded TC Reference MBX. by Bill Baker, Response Audio.with two separate mono power supply unit as same as preamp L2, Mac Mini, Offramp 5 USB convertor, DIY Duelund wire RCA IC, XLO Purple Rush power cord
Zen Mystery Amp. MIT Oracle RCA IC. Synergistic Research Tesla Reference power cable.
Avalon Avatar speakers. MIT Oracle speaker cable.
Hydra 8. ZSB. Kubala Sosna Emotion PC.

I have modded my Decware Zen Mystery amp by removing volume pot out of signal path. It improves much substantial transparency and dynamics to my system. I don't use any preamp. The source Audio Note DAC is connected directly to Zen Mystery amp. So that I need to have volume control for my amp. I read a lot forum about active premap, passive preamp and all types of volume control from volume pot, shunt resistor volume pot, Auto Transformer volume control (ATVC) and Lightspeed attenuator. My decision to go with Lightspeed attenuator.

I love my system to have amp connected directly to source, no preamp. The sound is fabulous. I temporarily use digital volume control in Pure Music software while Lightspeed attenuator was not arrived yet. The digital volume control is acceptable but still creates some sound distortion that you can hear.

When Lightspeed attenuator arrives, I connect it between my amp and source as a preamp. I hardly hear any different between having lightspeed attenuator in my system and without it in my system. It is so transparency. I give 99.5% transparency to directly connecting between amp and source. The 0.5% transparency short is for need of extra one interconnect cable which affects on sound quality. I am very happy and highly recommend to use Lightspeed attenuator as your preamp if you love your amp directly connecting with your source. Or your source has a very excellent sound and you don't want preamp to change its sound quality. And your system don't have any impedance mismatch with Lighspeed attenuator.

For active preamp, therea re some benefits because there are two more functions in active preamp which passive preamp does not have;
1) Gain stage function. Its function is to increase voltage of signal to improve loud and dynamics of system.
2) Buffer stage, its function is to prevent impedance system mismatch. If your source sound is harsh, buffer stage may help to reduce harsh sound.
Then active preamp is benefit for some hifi system.

You select the best for your system.
ch-hifi
1 posts
 
I've now been using the Lightspeed attenuator for some weeks with my Accuphase P-500 Amp; and I must say that I am pretty amazed and very happy with the sound quality! I would define it as very "clear" or "transparent", which fits my taste.
As I'm using the LSA on my main system, I will certainly add an input switch just to make it more convenient to use on a "normal" day.
I don't know if this is the best pre-amp ever (I just don't have the means to compare with other real contenders), but I'm convinced that for that price it would be damn hard to find something that comes close to this sound quality.
vyokyong
23 posts
 
Hi,

I just modded Light speed attenuator by replacing stock RCA jack with WBT 0210-Ag RCA "Next Gen" Pure Silver in signal path, Female Jack. I have modded my Zen Mystery Amp by replacing stock RCA jack with WBT 0210-Ag (Ms - metal nut) RCA "Next Gen" Pure Silver in signal path, Female Jack. And sonic improvement is huge in term of transparency, transient and micro-details. Then I want Light Speed Attenuator to be modded same thing.

This is instruction from George of how to replacing stock RCA jacks.

below are the opening instruction, if you change the rca’s they must be full bodied metal, as they have to have electrical contact from their body (which is earth) to the Lightspeed chassis on all 4 rca’s.

1: Remove two only top screws at the back
2: remove all 4 screws at the front.
3: Pull out front panel and bezel only about 10mm and lower.
4: Slide top plate out from the front.

But the RCA jack WBT Next Gen Silver 0210-Ag body is plastic, not metal. So that they cannot be ground through chassis contacting point at cut whole bare metal. Then I use silver wire to connect all ground point of RCA jack of both in put RCAs and out put RCAs and ground to chassis at one point only.

Result is that my Hi Fi system can play louder than before. It may be 1-2 dB or easily to hear different loud. Second both hi and low frequency is more extend with better dynamics contrast. The improvement is dramatic better and it is worth every penny to replace stock RCA by WBT RCA jack of pure silver in signal path.

However I think that using direct wire to connect between ground or negative points of both in put RCAs and out put RCAs together has affected better sonic improvement. (instead of using back panel aluminum plate as ground path). The Light speed attenuator owner can do simple modification of Light speed attenuator by using good quality wire to connect all RCAs ground together to improve the sound quality.

Hope this information will be helpful.
marqmike
839 posts
 
Thanks for the heads up on that Vyokong. Give us some more impressions after you have had them a couple of months. Thanks again.
vyokyong
23 posts
 
Thanks Marqmike,

Yes, I will.
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