2. amps-preamps
  3. 1276356977

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
Post removed 
swampwalker's avatar
swampwalker
5,138 posts
 
The irony about "simple" designs, with fewer parts, etc, is that it really requires some design chops to execute a great, simple circuit and I suspect it requires a master like Nelson Pass to design some great First Watt and XA.5 amps with such apparent simplicity in lack of complexity.
Or as my fellow Nutmegger Samuel Clemens once wrote:
"I'm sorry that this letter is so long, but I didn't have time to write a shorter one".

Translating this to the post I quoted, it's usually easier to fix a problem by adding a bandaid than it is to go back and rework the design to eliminate the problem.
grannyring's avatar
grannyring
6,526 posts
 
Clio09, nice job indeed and I have a question for you and all. Seems then all the high end preamps, tube or SS, costing up to $100,000 that are not passive, just can't get it right? Or should I say as right as a passive?

Wonder why all of these manufacturers even bother? Wonder why they are considered by the "experts" as the very best.

Perhaps a passive conspiracy..just kidding.

Let's assume my active preamp is more noisy then the LSA. If it outperforms the passive in many other areas, then it may still be a preamp truer to the recording. Benefits outweigh the short comings kind of thing.

I so want a $450 passive to sound as good, or closer, to my active. I tried several passives with no luck yet. Perhaps I need a tube amp like the RM10 and some high efficiency speakers. While the Atmasphere Ma1 amps had a 100K ohm input impedance perhaps my Soundlab's just did not like the signal from that combo. It was 2D and quite thin. Very clean, quiet and detailed, but kind of white - washed. It reminded me of some Nuforce amps I once owned.

I will say the LSA had great promise when I first put it in my system. I did take notice of how much quieter it was for sure. I also noticed it was smooth and extended in the highs. I also found the bass to be pleasing. Over time the white-washed nature seemed to reveal itself on every CD I played. If I played the LSA and had to make a decision after 30 minutes it would hard to pass it up. After longer listening I became fatigued.

Something tells me my Soundlab speaker/Atmasphere amp combo just preferred an active unit. It would have been very interesting to hear the LSA on my previous Silverline Bolero speakers with the same amps.
georgehifi's avatar
georgehifi
10,312 posts
 
If I can take this tube microphonics a step further for those who have tube preamps.
Try this little experiment.
Take the top off the tube preamp and turn on your system and set the volume control at your normal listening position. Then with your finger nail flick down the tops of each tube and have someone listen at the speaker for any sound comming through the drivers. This will show which tubes are microphonic. And in the case of really bad ones it will be heard out in the kitchen. And really really bad ones will feed back to the said tube and cause a runaway effect that can't be stoped.

Cheers George
georgehifi's avatar
georgehifi
10,312 posts
 
Just to add to my previous post on microphonic tubes, if you hear a bonk in the speaker because of a slightly microphonic tube/s, this in turn when playing music will give and artificial effect of adding ambience/echo to the music, if that your bag so be it.
But I will always be in the camp of what goes in should be exactly what comes out, nothing added nothing subtracted, warts and all.
Cheers George
More to discover