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
knghifi
1,668 posts
 

01-06-11: Pubul57
I understand why a moving coil cartridge would need gain (and RIAA equalization) to create a sense of drive and dynamics, but why would a 2 volt signal need any gain to drive an amp that plays at maximum output with 1v of input? Is "drive" something different than simple voltage which is either sufficient or insufficent to drive an amplifer? I suppose a source could have a weak output stage, but I would think that would be as much of problem for driving an active preamp as a more direct connection to the amp. There is something appealing about "horsepower", but does it really serve any purpose where input sensitivity is simply not an issue? Does an active really provide something "in reserve" for hearing micro and macro dynamic inflections?

01-06-11: Georgelofi
Sources these days, esspecially CD can drive (have enough output) by themselves (without the need of a preamp) a poweramp into cliping, there is your strait wire with no gain (the interconnects only).
All we need is something so we can attenuate that source so it doesn't blow the amp up, we do not need a preamp that preamplifies again on top of the source that can already by itself blow an amp up with the amount of output it has. ...

Years ago I had a Krell FPB300 and FBP600 at the same time. They are identical in design except for the power rating. Both are high current and power doubles down to 2 Ohms. My speaker at the time was Gallo Nucleus Reference ... forgot the exact model but one with 2 balls and a can on top. On paper, the FPB300 was more than enough to drive them that can blow out the drivers. But the FPB600 was much much superior in every way. You can feel the extra power, dynamics and sound was more relax with an ease.

Sometimes what's on paper doesn't tell the whole story in a real world application.
marqmike
844 posts
 
Hello everyone. I hope I did not sound condecending on my last post. I just wanted to share my view. Everybody here has shared theirs in a positive way, and no doubt helped others that read them. Personally I hear a big difference between actives and passives. What I mean by big, it is big to me. It's when I sit down and spend some time with other equipment accesing it. It is not always right off the bat I notice I don't like its overall presentation as well. I have had a few passives and actives(mind you not over $4,000.00 though, so not super high end but some good ones. That being said all my passives have been very sensitive to everything I do around it. That is both good and not so good. It is good in the sound it results in but in can be a challenge to get there. But when you do it is like the important nuances of sound going from a newspaper color to a high quality magazine color. When I say sensitive I mean everything in the chain. That includes speakers and might be why Grannyring hasn't met his preconceived expectations with the LSA. Yes power on the back side of speaker can help some but in my experience(I don't mean super sensitive) the more sensitive the better, there is a point where insensitivity can negate benefits of a passive in my experience. I no there is no same absolute standard of neutrality for everyone but in my experience if a source does not sound good behind a passive something down the chain is changing the signal to sound better. Source as is cables and amp all are very important when evaluating a passive. Clio09 said it way back when. He said something like you really have to build your system around the passive. But to me that is a really good place to start. Enjoy your music.
pubul57 OP
3,712 posts
 
I suppose moving forward we need to get away from what is better, or trying to prove it, but perhaps just hear what experiences folks have had. I expect there will be split between the passive and active sides from a head count perspective, but it is always nice to hear from other folks and their observations. The truth is there is a lot of great equipment out there for us to listen to, but I do want folks to feel that it really is possible to have what some very experienced listeners feel is SOTA for their systems for the very low price of the LSA. Especially important for audiophiles or budding audiophiles on a budget and more of us are probably in that situation than 3-4 years ago.
pubul57 OP
3,712 posts
 
Knghifi, I', not familiar with the Krell gear, but I assume the 600 has alot morep power than than the 300? I don't want to get side tracked on the power amps, but I think power and current and amps and how they interact with speaker impedances is a different kettle of fish than source volatage and preamp input sensitivity, I say that thinking I am right, but knowing since I am not engineer. That being said, and just as an aside, I would also argue that the exact same circuit, but for power output, the lower power amp will sound better, IF, the power and current needed for low impedance swings for bass, is adequate. But, I think that is another conversation, but a variation on the less is more paradigm (when less is sufficient, not always the case).
pubul57 OP
3,712 posts
 
made a few grammatical errors, there, but I hope you get the gist of what I was trying to say. By the way, the new Dylan Mono Recordings Box sounds great.
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