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.
I agree with you that with a resistor-based volume control, the extra voltage is discarded in the form of heat. In addition the more resistance that is applied by the volume pot, the more the signal is compromised – usually in the form of compressed dynamics.
It is important to note that the output voltage specification on a source component represents the maximum output level when playing a disc that is recorded at the very highest possible recording level. Nearly all CDs are recorded at a level where the musical peaks never reach the maximum signal level that can be recorded on the disc. As a result, very few discs will ever result in the CD player outputting its full 2V potential even when playing the loudest passages of music on that disc.
So I believe, even in case of Lightspeed a high output volt from the source is better for the sound quality. I mean, I would any day take 3.9V from source over 2.0V.
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).

What is this CD you talk about? Is it some kind of new format?

Obviously recording levels are all over the map and ultimately it is up to the end user to educate themselves and see what works for them or be doomed to repeat the same mistakes.

These are all simple attenuators and they must exist in some form in every system. Who decides which box they go in and what they are termed is just a matter of semantics.

I say learn to think outside the box and get your gain, headroom and impedance structures inline then choose the attenuator that sounds best to you.

I have to eat a little crow.

I posted earlier that I preferred my Supratek linestage to the LS due to an added dimensionality and warmth that tubes offer with all other thngs being equal between the two.

Well, reading this threat spurred me to put the LS back into my system for another listen. I'm glad I did.

The first time I compared the two I simply connected the LS to my system with it sitting on a cardboard box on the floor. This time I went to the trouble to take my Supratek out of my system and I put the LS on the same shelving and footers I use with my Supratek.

This time I must say the LS is slightly more transparent, with equal slam, warmth, tonality soundstage width, etc. The only area that may be up for grabs is on some recordings the soundstage is slightly more forward with the Supratek. I'm not saying that is a better thing, but rather a simple difference.

To be honest, the two are so close that I have to really, really, really try hard to tell the two apart. I listened to several recordings that I know exceedingly well and I swear had I not known that I took my Supratek out of my system, I don't think I would have noticed.

The biggest problem I have with my Supratek is getting good 6SN7's, both NOS & current production, that don't have issues at some point, i.e. microphonics, loud hissing (not typical tube noise), whistling, cracking & popping, etc.

I just purchased a pair of the new Shuguang Treasure CV181-Z to try. They sounded as good or better than any NOS 6SN7 I have ever tried, including TS RP and 52 Bad Boys. However, one went extremely microphonic between 30-40 hours. As much as I love tubes, they frustrate the crap out of me at times.

So, I am sticking with the LS for the time being. I tried to be as objective as I could between the two preamps and when comparing apples to apples (same shelving & isolation) I have come to the conclusion I don't think I could tell them apart in a blind test.

Thanks for an incredible product George at an unbelievable price.
I've been following this thread for some time. A couple of recent comments by Fiddler hit very close to home.

As much as I love tubes, they frustrate the crap out of me at times.
I tried to be as objective as I could between the two preamps and when comparing apples to apples (same shelving & isolation) I have come to the conclusion I don't think I could tell them apart in a blind test.

Fiddler (Threads | Answers | This Thread)
While I can tell the difference between my present tube preamplifier, and my passive (with JFET buffer) preamp, there is only a small difference, and the fact that the passive will sound the same 20 years from now, and that it uses significantly less electricity makes it a compelling keeper.

If one's system can accommodate the Lightspeed Attenuator, there are excellent reasons to own one.
Does anyone how where or how to buy this preamp. I have tried to contact the manufacturer using the email from their website, with the intention to purchase, but there has been no response.
[email protected]

This is the email I use to contact George. Between the Stereophile article and a few recent threads I'm sure his time has been a little more consumed than normal. Also, you might be going into a spam filter. Hopefully he'll see your note here.
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:)
Does anyone how where or how to buy this preamp. I have tried to contact the manufacturer using the email from their website, with the intention to purchase, but there has been no response.
Oops, posted the same question twice...

Clio9, that is the email address to which I sent the quiry. I wanted to know if George accepted paypal or preferred CC transactions. I also wanted to know shipping costs to the UK. I sent two email within a period of two weeks. Perhaps George is on holiday.

He's been posting here of late so I doubt he is on vacation. I suspect your email may be getting caught in a spam filter. George usually responds to emails within a day or two.

I bought mine from George using PayPal. I don't think he takes credit cards. Let's hope he sees your posts here and can contact you through the Audiogon system.

Be patient, it's worth the wait.
Zendent7 E-mail George thru Audiogon. I also used his website address with no responce. E-mailed him thru Audiogon and he answered within 1 hour.
Zendent7 Does anyone how where or how to buy this preamp. I have tried to contact the manufacturer using the email from their website, with the intention to purchase, but there has been no response. Zendent7

Zendent7 you can email me through the Audiogon Industry Directory

Or the Lightspeed Attenuator website
And I will send to you PDF pricing/shipping/sales brochures. And remember as says on the web site remove the spaces before and after @ on my email address

Cheers George

Also Zendent7 I get about 50 Lighjtspeed inquiries per day, the only one I have had trouble sending to in the last week was this one if you are tag*** I cannot send anything to you, not even an email let alone a PDF as your provider earthlink is hell bent on blocking anyything, I've tried everything, it's so frustrating getting emails bounced back.

Cheers George
Ooops! 50 per week

Cheers George
With quality products like Supratek and Lightspeed coming from Australia, there may be a movement afoot from "flat earthers" to the "down unders".
We just let you guys in the Northern Hemisphere do all the groundwork ...... :-)
06-19-10: Pubul57
With quality products like Supratek and Lightspeed coming from Australia/Australasia

For the amps list you should add: Halcro, Cymer, ME, Asaka, SGR, Redgum, Electra, Amber, Earl Weston, Aspen, Plinius (NZ), Perreaux (NZ, )

Just to name a couple
Cheers George
I heard a Redgum integrated recently, it sounded quite good and was well built.
Anthony, let us know your impressions when you hear The Truth preamp.
Hopefully will have it in a few weeks. Ed Schilling at the Horn Shoppe builds them one by one and he has a bit of a back log right now. I'll probably start a new thread at some point in the future to provide some feedback and comparisons.
You must be joking. I've just heard the lightspeed attenuator in shootout with the Firstwatt B1 and the B1 killed the lightspeed in terms on dynamics. In fact I could not recall a single aspect where the lightspeed would be better. These are my thoughts only and do not necessarily represent others.
Clipsal, what were the other components in the system in which you heard the shoot out?

The B1 is an excellent product. Nelson Pass also has published schematics for his own version of the Lightspeed. My take on his development of the B1 is that through the use of an active buffer stage the preamp matches up much better to the low input impedance First Watt amps he designs.
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 also would like to know the poweramp used in this shootout and also the CDP or DAC.

Cheers George
Why doesn't this link show up in the forum section any longer? I had to do a search to find it.
I noticed that too. Odd.
We're back, thanks Audiogon support.
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.
What I am most curious about is how well The Truth preamp will drive the S-30. The LSA does drive it well, but I'd like to hear if The Truth will improve upon dynamics. The bandwidth measurements are off the charts with the Truth and the output impedance is a constant 2 ohms. Apparently the input impedance is too high to measure.

No risk to try it so we'll see.
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!!
About buffers, I will always say the best buffer is no buffer if your system meets the following impedance requirements. If your source output impedance is less than 200ohm and your poweramp input impedance is more than 47Kohm then the Lightspeed Attenuator is a shoe in, no buffer will sound better.
But if your source is more than 200ohms output impedance or the power amp is less than 47Kohm input impedance then you may (but not always) need a buffer, the best commercial buffer I've heard is the Burson Buffer. But the best sounding buffer is the (diy) Super Linear Cathode Follower (SLCF) buffer. But still they don't sound as good as NO buffer at all.
P.S. those who want the circuit of the SLCF send me an email
Cheers George
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.
I just started running the Lightspeed off a battery power supply. It is the same batter power supply used by Galibier Designs to power their turntable motors (Sears Diehard Portable Power 750), 12V DC and 12aH. Thom Mackris made me the appropriate adapter cable (mine needed to be center pin negative). I've been listening for a bit now and so far I like what I hear.
I also use a Lithium Ion rechargable sometimes, I hear a difference but cannot pinpoint what it is, even on a very hi rez system.
They say the Lithium Ion has the least chemical bubble noise of all batteries. Sometimes I forget which one I have on, the battery or the wall wart it's that close.

You can get these batteries on ebay from Asia for around $20 with international charger, do a search for Lithium Ion 12vdc rechargable usually made for cctv cameras were low noise is a must, just make sure it's center positive for all the production Lightspeed Attenuators I have made as I do not want to have to repair fried componets if I can help it. Yours Clio09 is the only one I think I made center negative I forget the reason why. They have about 12hrs constant use before a recharge of .5hr
Cheers Georgehifi
Anthony, is you battery charger commercially available? Have a link? Also, what about the point George raises regarding the Center positive/negative?
Mine was made center pin negative because the wall wart George recommended was set up this way. For the battery power supply you can find it here:

This will allow the Lightspeed to run much longer than the Lithium Ion George recommended.

You will need an adapter cable that plugs into the 12V DC outlet on the unit. Here is an example of one (although they are sold elsewhere too):

You need to scroll down the page and look for:

Power Plug with 2.1mm X 5.5 mm
Coaxial Plug with 18 AWG 8' Cord

The cost is $5.95

Just make sure it is center pin positive.

This battery power supply and the adapter cable are used to power the motor pods of Galibier Design turntables. These aren't inexpensive tables so I trust Thom's choice in parts.

Thom procured my cable and wired it for center pin 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.
This kind of shared info is greatly appreciated. I am getting a LSA, and I don't even know if it will work. But I use a passive now(Sumo Athena in passive mode with a Sumo Polaris amp, it has about half the gain than the active side but sounds better), so I am hoping it will. What I would like some of you with experience with the LSA to share and keep going with this thread, what is a good(excellent sounding) amp and cd player to use with the LSA specifically? When I get mine and use it I will give my thoughts. Thanks.
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.
If you buy this off the shelf, is it center pin positive by default?

If you buy what off the shelf?
Marqmike: The amp should have greater than 50k input impedance, more is better. Input sensitivity isn't as critical. Typically 1V or so would suffice, but I've run my LSA with an Atma-Sphere S-30 that is nearly 3V sensitive and it works fine. I even tried it by altering the amp to be even less sensitive (nearly 6V) and it was still fine, although I was running out of room to advance the volume control. It is also important that your source output impedance be low, 100 ohms or so, and have enough output voltage to drive the LSA, 2V or more.

As mentioned, you need to worry more about the amp/speaker combo when deciding what components to use with the LSA. Given that the above requirements are met, the LSA is benign in the scheme of things.
Thanks Pubul57 and Clio09. My amp has input impedence of 47 KOhms and input sensitivity of 1.27 Volts rms, my source has a output impedence of 120 ohms and output voltage of 2 Volts. It is close to what you and George S. recommend so it should work. If not it might be time for some newer items, mine is over 20yrs old. It sounds like this could be a great reviewers tool? Thanks for the input.
Hi Anthony. I meant the battery and connector you provided links to. Would it be a plug&play purchased as is? In terms of the negative/positive pin issue?
The battery is plug and play. The link to the connectors show several. The one I indicated is the one you want. It is center pin positive. Most are default that way, but you need to be certain as reversing the polarity on yours with a center pin negative connector will damage it. The information for the one I referenced says it is "inside positive" which means center pin positive. Buy this one with the battery and all is plug and play.
I've contacted RH at "tas", and raved about the Lightspeed. I have had both SoundLab electrostatics, and Magnepan 20.1's, and I am after purity, with no added colorations. I have owned several amps of different circuit designs and preamps, tube and transistor, active and passive. The Lightspeed in the audio chain is non-existent, everything that's on the recording is there, nothing more, nothing less ... perfect. I mentioned to Mr. Harley that when I read Jonathan Valin saying he misses the "bloom" and "spaciousness" of tubes, with ANY piece of equipment, I cringe. If I want to hear phase manipulation or harmonic distortion, etc., increasing the stage depth and image width, it ought to be on the recording, not being created by my components. I see this elsewhere in criticisms of passives, and amplification in general. If someone wants to alter what the recordists have compromised, then, an equalizer is in order. The real music is At The Venue, anyway. It's pretty disturbing, as well, to think what monitoring speakers or headphones recording engineers may be relying upon to record in analogue OR digital. As an insane lover of this hobby, and an ex-musician in love with music, I know that the sound I'm getting also relies on the careful system matching of associated equipment (which is equalization of a sort, in itself, but those pieces have inherent sounds of their own, unlike this attenuator) ... interconnects, amp circuitry, speaker transducers, "wall-power" purity, transport or turntable mechanisms, server quality, ad-infinitum. The Lightspeed may have it's own system-matching limitations, but it's absolute transparency is exactly what I want any component to emulate. No sound of it's own. If I can't be at the performance, I'd like the source recording to be good enough to allow me to enjoy the music. I hope the Lightspeed gets into homes where it is understood and appreciated. This thing is a treat, absolutely incredible, and the price makes it affordable for just about anyone.
Robtn, obviously I could not agree with you more. It was interesting to hear you say, "I mentioned to Mr. Harley that when I read Jonathan Valin saying he misses the "bloom" and "spaciousness" of tubes, with ANY piece of equipment, I cringe. If I want to hear phase manipulation or harmonic distortion, etc., increasing the stage depth and image width, it ought to be on the recording, not being created by my components" because I recently heard from a well-regarded Audiogon member who told me that he has a shoot-out of sorts with LSA and 4 or 5 very highly regarded tube preamps (really good line stages)joined by a group of audiophiles. While they felt the LSA was very good in terms of clarity and transparency, the one area they felt it fell short was in this very area you mention related to spatial representation and dimensionality. But this must really be an issue of preferences as I too get the sense that what imaging is there should be real and from the source and not what you might describe as an artifact, a distortion of sorts. To me, the LSA sounds like what I am looking for, but obviously it might not be everyone's cup of tea. As you point out though, for $450 or so, it is well worth trying without too many preconceptions about tube/ss/passive and just listen, for some listeners, especially those with tube amps the LSA might be as good as it gets. Listened to SACD version of Adderly Somthing else - incredible timbral accuracy, dynamics, and resolution - but a very dimensional recording as recorded.