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

Showing 50 responses by pubul57

I am a little confused - the compression is an impedance issue, not a gain issue?
Was your S&B TVC a DIY job, looks nice. If so, have you considered trying a Slagle AVC?
Has audiogopn made it impossible to get, and use, e-mail contact information for other members?
Of course, the LSA Ultimate would allow for buffer switching :)
It is linear. I, we?, sometimes hear what I expect to hear, at least in the short term.
That is what I suspect, 2db would not be as useful as one would hope, but I'm speculating, not having tried it.
No 1 meter IC I know is likely to create any capacitance issue:)
The "Heather Test" has officially entered the Audiogon lexicon, and I suspect we all do it and rely on it from time to time:) Now, where did I put the Chianti....?
Maybe it is the input impedance of the LS that is constant? I've confused myself (again).
I meant to say 50kohm input impedance or higher for the amp, not 5kohm - that would not work at all:)
My interest in passives started when I read on Arthur Salvatore's website "if your source is up to the task of driving your amp(s), then no active linestage, no matter how good it is, will ever equal the sonics of your direct connection (or an equivalent passive)". This coming from a tube-centric audiophile made me ponder this for a long time. He goes on to describe the circumstances under which an active linestage would be needed. I read this and left this continuing with my various tube linestages, not sure if it was warmth I was looking for, but certainly dimensionality which I always found lacking in SS preamps.

Then I bought a couple of amps from Roger Modjeski, the Music Reference RM9SE and RM10s. Knowing he could design anything he wanted to, I noticed that he made the move from active tube linestages to passive and asked him why, this guy obvioulsy loves the sound of tubes, not only making gear with tubes, but also the best tube tester on the market, and he said just what Salvatore said, no active line stage would be better than a high-quality pot based passive with his amps (100kohm input, and high sensitivity). Asked about buffers, tranformers, blah, blah, and he said I can make you whatever you want ("I'll put a tube or two in it if it makes you happy"), but he repeated, nothing will be beat a passive preamp with no buffer IF mathed correctly between source, cables, and amp.

As to Fiddler's comment on warmth and dimensionality, I have to say we all want dimensionality (as long as it doesn't come at the expense of timbral accuaracy)and in this aspect I do not feel any loss of this important aspect compared with my Joule and Atma-sphere preamps. The area of warmth is a little more difficult to put my finger on, perhaps more subjective, and prone to the influence of preference. I will say that he idea of "adding" warmth is not something I am comfortable with, but that is just me, with the LS I feel I am getting as much warmth or lack of it as is in the source. The apparent warmth will vary with the recordings, and that is a very good sign to me, that is when the sonic attributes of a piece of gear change, or is dictated, by the recording - it tells me the gear is not putting an overlay over a recording that can be heard regardless of what one might find in the recording itself.

What I find with the LS is that the issue of soundstaging, dimesionality, apparent bass and highs, etc. is dependent on the recording, and for my approach to building as system, this is the way it should be, but that does not mean it is eveyone's cup of tea regarding the sound they are looking for.

But, these are all words, which don't mean a thing compared to trying one of these things in your system, knowing, and accepting, its ergonomic (one input/output) and electrical (gain and impedance matching) limitations, and judging for yourself.
Grannhyring, just to give you some context, my view of the Lightspeed is as a current and former owner of several highly regarded tube amps from Lamm,ARC.Joule, CAT, and Atma-sphere. Not that it proves anything, but I would not like this thing if it was in the least bit small, sterile and thin relative to anything. If the tube pres I have owned, and still own, are not the very best, they are close. The fact that this thing is $450 can hurt it for those use to 10K preamps.

Alas, it is not for everyone with its one single-ended, single input, but this thing does not sound like any of the stereotypes of passives, it has the signature of clean water, letting the source connect to the amp with minimal interference, without loss of any apparent bandwidth, or dynamics. It is not a bandaid preamp that will fix whatever isn't quite right or to once's taste in the rest of the system. A great source with a great amp and speakers are where this preamp will work best, even in the company of $$$$ components before it or after it. My feeling has always been that the preamp should be as neutral as possible with the coloration one prefers coming elsewhere in the system - making it more universally easier to use in many different system contexts.

I hope this unit is used by someone at RMAF so everyone can actually hear it and decide for themselves if it provides the type of sound they can be happy with. It would be nice if there were a 30-day trial, but I'm not sure if the low price and the long-distance transportation would make that viable - it is certainly light enough to ship around.
You may or may not like it better than your unit, we all know that we personally gravitate to what we want, what we like, and what anybody else says doesn't really matter, IF we can trust our own ears and preferences, all I am saying about this preamp (semantics aside, I don't need a source selcetor) this thing is special in away that the other passives I have tried have not been able to match, and obviously has gone up against some pretty renowned tube preamps where at least some folks have concluded that it is preferable. So all I am saying is that as we seek the best sound avaialable, this $450 peramp (thing) is worth a try, even if at the end of the day you decide to stick with your active (tube?) preamps.

Maybe George HiFi will be able to figure out a trial scheme that can make sense to him, though he may already may be limited to how many he can make per month so I may be a moot suggestion. While I will use the Atma-Atma combo with balanced cabling, my other systems combos are going passive with the Lightspeed.
You must order directly from the maker in Australia. A google search will help you find him. I get the feeling he is an individual making a few of these and he pursued this without the idea of starting a real business, but word-of-mouth has proabably driven more business than he expected, so I have no idea how long it takes form him to make and deliver, especially after Sam Telligs review which essentially reached the entire North American audiophile community. He does have a minimalist website.
I wish I were going to RMAF this year, that steak house was great and the Audiogon party at the Mexican restaurant was a hoot - have fun!
Wait till George takes out a year's worth of cover 4s:)
Apparently something like this was once used in the Melos preamp years ago, and in the current DarTzeel (something like it).

I finished my last post by saying try it, since it is almost impossible to avoid cliams of overhype when talking about a preamp most have not heard, and lord knows there have been many flavor of the month, buzz pieces that are long forgotten shortly thereafter. So all I can do is recommend you try it if it might fit your system.

I only offer the context of my views, as a previous owner of many passives that left me feeling like those here that have expressed dissapointment with there efforts at using a passive. First of all I have owned almost every passive of the past five years of all the basic desing approaches and always preferred my active tube line stages. As an interesting point two of the folks that like the Lightspeed have also owned Joule preamps which are on the warm, musical, meaty, organic, etc side of the preamp spectrum, so we know that sound, and in that context, the LS does not dissapoint - it is not cold, sterile, lifeless, flat, missing PRAT, etc. Now, I don't know how to address the warmth issue, since two of my favourite preamps are the CAT SL1s and Atma-sphere and they are not known to be "warmth-lover" preamps, so it may be I don't find warmth as seductive as others, though I do love my Joule LA150 Signature Edition which is warmer than the other two.

Yet one cannot predict how each of us might react to this thing, which is why I say you have to try it and decide for yourself, if it was $5,000 I would want alot more evidence and listening sessions, but for $500 it is within reach of most of us in the forum to decide for ourselves without coming to conclusions drawn from sources other than our own ears.

Best preamp ever? I do think that is a silly question, or at least silly to believe such a thing exists, it does not and cannot. But, the Lightspeed is very, very good, and sound like this from a $5-10,000 preamps (the price of my last five tube preamps) would be great, at this price it seems like a must audition, at minimum, for those on a budget with something like a Music Reference RM10 (1k-2k - used/new) and 89/90db or higher sensitivity, flat impedance speakers for a first rate system at an "affordable" price. For those with plenty of $$$ to spend, at this price it is simply worth trying for yourself and draw your own conclusions.

Even if it does sound as great as I (and others that have heard it/ owned it) am saying, it still will not be the preamp for everyone, since it is VERY limited as a source selector, and does require a source, short (2m) ICs, and amps that can work with a passive - not all can. Just as I would not make claims about 4 watt SET amps sound like from listening to them on a pair of B&W 802s or Thiel 3.6s - I exaggerate to make a point.

If you live near Baltimore, come over for a listening session and compare it with my Joule and Atma-sphere setups and tell me what you think, easy enough to compare.
Anthony, Roger Modjeski was gracious enough to explain to me why he thought resistor passive would be theoretically better than tvcs or avcs (the Audiogon consensus was that TVCs were far better than resistors, that TVCs 'blew them out of the water - which always seemed an overstament), but you know how he gets with technical explanations, he quickly lost me. When I had the Placette I like it very much, and I do think it might be fruitful to go back for comparison, but I suspect that the fact the Lightspeed has no physical contact points, no mechanical interface, no oxidation, no wearinmg out with time and swipes, might be an unbeatable advantage, even for Swiss crafted, jewel-like, precisely machined or lazer edged attenautor contacts:)
Lightspeed Attenuator, Best device for controlling volume in an audio system ever? including "real" preamps?
I agree Anthony, as enjoyable as several $10-$20,000 combos I had here over the past 5-7 years. With the right speakers, the LS-A/RM10 combo($2,400 list)is incredibly good and competitive with just about any pre/amp combo out there, at any price.
Arthur Salvatore also says, in an interesting way, that if your systems sounds better, in any way, than a direct connection or passive, then your system needs and active preamp (he says most systems do) - because in some way your just not matched right. AS' views is that passive is the best, unless you need active. I'm pretty sure my system does not need an active for gain or impedance matching and therefore it is unlikely that any active preamp or volume control/gain device will improve over what essentialy (as George points out) is as close as you can get to a direct connection between my source and amp.

If amplyfying that signal through additional wire, capacitors, transisitors or tubes etc, only to attenuate that additional gain can some how improve on the original source signal, I just don't see how it can do that unless that signal needs all sorts of conditioning to drive the ICs and amp. My 2v or 3.9v outputs from the EMM Labs CD player don't need such help to drive the amps, and if there is dimensionality and warmth in a recording it is there at the output of the CD Player, not fabricated in an active tube or SS linestage - and if it is the byproduct of the linestage, I don't want to hear that as it will be an overlay on everything you listen to.
You can't argue with what people like, which is the only criteria that is important. I suppose the straight wire with gain approach is almost a philosophical stand, even when that might not necessarily result in the most enjoyable sound, a bad recording has no place to hide. This is proabably an issue that can never be resolved, there simply might not be a right or wrong here.

The Lightspeed does minimal (even compared to other passives) alteration to the signal (noise, distortion, bandwidth anomalies) and does this very well, if that is what you are looking in volume control (true to the source) it will serve you well.
I have never heard a stereo system that sounds like live music, but I have heard stereos that probably sound more the recording - the loss goes from live to recording and it only gets worse from their in terms of sounding live. If you don't go to live acoustic events you might get fooled from time to time, but then I go to a jazz concert and after a few minutes my audiophile mind goes ugghhhhh, and accept that stereo systems are just very enoyable ways to a enjoy music, some better than others, and none close to live.
I had to google it, hmmmm.
Thought well enough of the Lightspeed Attenuator, that I just sold my beloved Joule LA150 Signature Edition line stage($6,500,)as having two "real" preamps and a single-source volume attentuator seemed like too much gear, but I'm keeping my Atma-sphere pre for use with the Atma-sphere amps:)
Proabably getting quite a bit of warmth, dimensionality, palpability, and bloom from the Jadis. The Lightspeed Attenuator doesn't look too puny driving the Music Reference RM10s which are about the size of hardcover book:) - now if I still had my CAT amp....
Well we may never get to the point that we can say of any preamplifier (or volume control, if you will) that it is the best ever (a silly thought), but I feel pretty comfortable saying that this is by far and away the best such thing for the money, and not a poor man's option, but a true SOTA approach to volume control, in the right system.

Anthony, if you do give the Axiom a listen in your system, your thoughts would be welcome, not sure it would be better than a Goldpoint with the right value attenuator, or the Placette RVC for that matter, but I'm not sure what they are doing that might make a difference compared with those, even with the Caddock option (better than Vishay?).
I would think a room much larger than 12x18 would be too large for the RM10 with my Merlins which are 89db, the RM9s do have more scale (and 162 watts)so you would expect that, but they are closer than you expect, at 20% of the price of the RM9 Special Edition (not the standard RM9).

I'm not sure why the 87db would be an issue in terms of the LS, if the amp 60 watts or more tube, or 100+ SS, and if their input sensitivity is 1v for full output, the limit would seem to be the amp, not the LS in this situation, but perhaps George will chime in as I have not actually tried it:)
Also, on the RM10, I'm driving Merlins with its 35 watts (actually 27 watts since I use the 4 ohm tap) so it's not really trying to move large bass drivers which might show up the RM10s limitations, don't know. I do know that Roger designs his amps with electorstatics in mind, so....
I would say any tube amp you like with 100kohm input impedance and input sensitivity of 1v or lower. The rest is dependent on whether or not you like you amp/speaker combo.
George, do you think the quality of the power supply of the CD player would make a difference? Might not a poorly designed PS in the source benefit from the "conditioning" of an active preamp?
Anthony, let us know your impressions when you hear The Truth preamp.
The Cardas GR have really low capacitance, but the Blue Jean ICs, which are Belden made, also have very low capacitance - if that is an issue, which shouldn't be with most cables under 2m (I would think).
And ST is a "cheapskate"....
Anthony, I'm not sure if you would know this, but if a CD player can be switched for output level (The EMM Labs can be switched between 2v and 3.9v)is there any theoretical reason why one should sound better or different, assuming 2v plays loud enough? I imagine based on Ralph K's comments to you on "opening" up an attenuator, you would be better off with the lower voltage - though I'm not sure if Ralph's comments apply to the LS as I think it has the same input and output impedances at all volume levels (I think).
Actually, the voltage is 2v and 3.6v unbalanced. THe manual says output impedance is 50ohm, the brochure says 150ohms unbalanced - whatever it is, it seems to have no problem driving the Lightspeed Attenuator. Seems that there seems to be no reason not to use the higher output setting, and theoretically a good reason, though it does not seem like they are using a voltage divider (but just in case).
Fiddler, I was glad to see your post, to help me rest assured that I was not loosing my mind or going deaf:) I thought it was pretty good too. The fact that compared with the Supratek, and that I have owned ARC, Lamm, CAT, Joule, and Dodd, makes me feel that this things is indeed a very, very good piece in the right system. I trust Anthony's ears, but it is good to hear thought from another person with a top flight tube preamp. I sold the Joule LA150 Signature Edition this week, which I loved, becuase I felt that in my system (single source)with passive-friendly and no-gain needed, the LS is able to give me SOTA sound, or at least something as good as I was getting from some of the better tubed active linestages I have used. I don't think the LS is a flavor of the month product, and as Tvad point out, it will sound the same for the next 20-years or more.

Zendent7, not sure when you sent the e-mail to George, but he is in Australia, so he might be sleeping:)
With quality products like Supratek and Lightspeed coming from Australia, there may be a movement afoot from "flat earthers" to the "down unders".
Not joking, but of course system matching is key as Anthony. Love Pass gear, and heard the B1 at RMAF and it was very impressive. But so was the Bent TAP-x and I prefer the Lightspeed in my system since it is ideally suited for a passive with no impedance or gain issues - and far simpler device for minimal distortion. I have no doubt the B1 will perform better in some systems than the Lightspeed, but the reverse is true to, and then there is personal preference which is more difficult, if not impossible to account for.
I noticed that too. Odd.
So we wait Clipsal for the system context for you B1/LSA "shootout". Also for Anthony's assessment of The Truth preamp, which seems to be a hybrid between some of the desing principles of the B1 and the LSA. Other passive comments (Goldpoint, BENT, Prmoethius, and other resistor, TVC, and AVC comments welcomed). In my system with Music Reference RM10 and 9, the LSA is the best passive I have heard, and I have tried most all but for the B1 in my system at home.
Anthony, I've read the threads about The Truth preamp and it does seem to employ a similar "volume control" as the LSA (photo cell versus optocoupler, not sure if that makes any audible difference)along with input and output buffers. When I spoke to Roger Modjeski about his passives, as you know he has a plain Pot-in-a-box and also makes a version with a tube buffer stage, I asked him if the tube buffer version would be better, he said only if you need a buffer, otherwise the the the version without a buffer would be better. So it will be interesting to see what you find when you try The Truth. I suspect that since my system is in no need of a buffer, the LSA would like be the better choice. It does not seem like you need a buffer either, so your observations apart from "theory" will be interesting to hear.
George, obviously you could have made a buffered version of the Lightspeed, what are the pros and cons to that approach. What are your thoughts on buffering? Go Spain!!
Thanks George. That is pretty much what Roger Modjeski (Music Reference / RAM Labs) said and "I'll make you a preamp with a buffer, but you don't need it and it will sound better without it". Now Roger is a guy I pay attention to, he is an electrical engineer, make classic and much admired amps and preamps, and is a tube maven - he also is aghast as audiophile tomfoolery and nonsense. I've been drawing the conclusion that active preamps and even buffered or transformer based passive will sound better than a pure passive when the system needs it, and many do when the impedance and gain issues are not properly addressed, but that in a system metting the requirements for a passive (without buffer - not the Pass, The Truth, etc)something like the Lightspeed will provide the very best possible sound. It will be interesting to hear Anthony's observations of The Truth, since I do think his system is a good setup for a "pure" passive.
George, is it your view that the Buffering used in preamps, and passives like the BENT, The Truth, or the First Watt B1 is there for handling worst case scenarios - long or high capacitance interconnects, or amps with low input impedances, but where the ICs are low capacitance (Cardas GR 12p/ft) or high input impedances (100kohm)that a bufferless approach will always be superior? That is how I read it, and that something like the LSA is about as good as you can get in not altering the source signal to the amp.
Anthony, is you battery charger commercially available? Have a link? Also, what about the point George raises regarding the Center positive/negative?
If you buy this off the shelf, is it center pin positive by default?
Oh yeah, and we eagerly await your The Truth comparison.