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
knghifi
1,668 posts
 
George, I don't understand how the preamp not altering the signal from the source will accomplish what the recording engineer wants you to hear? Is it even possible?

By the time the signal gets to the preamp, it has already been altered (tone controlled) by the source (cdp, phono ect) / interconnect. For me, I want a preamp to improve the signal IF necessary so the overall performance improves.

With the LSA, I much prefer my MW Transporter than TRL Sony having some tubes in the chain. Also I prefer rolling the sweeter sounding Sylvania 6sn7gt than Shuguang BT CV181-Z. So which one of the 3 the recording engineer wants me to hear? Probably none due to my inferior sources? For an end user, do I really care or just configure my prefer setup? With the VAC, I like both source almost equally despite the very very different sound.

I think a passive preamp is more dependent on a good source/interconnect than an active preamp. If a signal is poor, passive just pass through while active can attempt to improve/bandaid.

In a sound system, the signal gets altered as it passes through a chain of components. My goal is to select the combination of components that best create the sound base on my personal preferences.
ngjockey
1,042 posts
 
I knew this thread was going to last like this when it started. It's getting to appear more like a perpetual promotion device.

If these things "don't add or subtract", why are they so hard to match? Can't perfection be duplicated?
pubul57 OP
3,712 posts
 
If you start with a signal from the source (all the information from the recording you can get), isn't any alteration from that simply an additive having nothing to do with the recording, but some haze thrown over the recording, pleasant thought it may be? Maybe I am thinking about this the wrong way, but the signal from the source is the purest reflection of the recording, and any alteration from that is something having nothing to do with the source, the recording closest to the event. It is some type of alteration. which can be nothing but an alteration that pleasant or not, is no part of the recorded performance. Might that be pleasant? Perhaps, but it is something not true to the recording, and if you accept that, it is only a question of how much you are willing to accept as the overlay of a piece of equipment, but how it can it be anything but a distortion from the original, I don't know. And of course the recording itself is already something lost from the live, presence of the original. A bandaid distorts everything in the same way, better in my book to have no bandaid, no coloration from the source. But this reflects fundamental principles of what the equipment should do to a signal, but no information leading to all the audiophile attributes can be good if it alters what is in the source signal, as best as it can convey the recording; the rest is something having nothing to do with the recorded event. Pleasant and enjoyable though it may be, it is not part of the performance and we are only left with coloration and variance from the truth - the truth contained within the recording transmitted through the source component to the preamp. The ideal to me would seem to be a transmission from the source to the amp as if no intermediary component existed, I think that is what the LSA comes close to accomplishing, and qualities such as timbre, sound staging, bloom, frequency, etc are either in the recording, or they are not, but you don't get something false to compensate for the absence of those qualities when they are absent from the recording.
pubul57 OP
3,712 posts
 
"If these things "don't add or subtract", why are they so hard to match? Can't perfection be duplicated?"

They are not that hard to match, you just need a tube amp or a high input impedance SS amp - gain is not much of an issue in most systems. But it is not a universal solution, that is why we have so many expensive linestages that are essentially plug & play into any system, what is lost is the simplicity and purity of a signal that isn't messaged to enable to work in any environment. So you can have a preamp that will work in any system, but compromised by the circuit complexity required for that, or choose a simpler device that will not work in all systems, but because of that simplicity provides a cleaner connection to the recording if not challenged by impedance mismatches. A little more work to get it right, but well worth it if you want to take this approach. I'm sure George would make a universal device that could work in any system if he could, but it just doesn't exist. This is a minimalist approach that can lead to great sound, but it can't work without some thought given to the source, cables, amps, and speakers.
fiddler
581 posts
 
"...purest reflection of the recording..."

Excellent post Pubul57.

When comparing my Supratek to the LSA, I did find the Supratek to be just as transparent without any "usual" tube colorations. I was actually surprised that the Supratek is as neutral as it is being a tube component.

Where I found the LSA to be very slightly better was in the lack of any sibilance. Admittedly, I only heard a very slight amount with the Supratek, but I HATE sibilance. So in the end, the LSA and my Supratek sounded almost identical to my ear. The only area where I thought the Supratek may be slightly superior was in the depth of the soundstage.

In the end, the LSA seems to give me vitually all of the positives of my Supratek without any clearly identifiable sacrifices. The good news is that the Supratek seems as transparent as the excellent LSA passive and the LSA seems to be as bold, dynamic and full-bodied as an outstanding, highly-regarded tube preamp. They both are excellent.
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