The short answer to your question is yes.
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 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.
Showing 50 responses by clio09
I have sat in front of many systems that measure great but sound rotten. So, I have no need to help out poor Sam Tellig, just to point out that techno-babble that says the same thing over and over again on this thread does not prove that George's LSA is in some objective way better then active linestages. Then why reference him? What was the point? Are you just trying to point out someone that has an opinion that agrees with yours? A lot of people do. You're right in some respects our ears are the judge and it's obvious there are quite a few people who prefer the LSA on this thread, for whatever reason they wish. Like you prefer your Black Box but scientifically can't explain why. If you have an objection to George posting here well deal with it. It isn't the first or last time it will happen on Audiogon. I welcome manufacturers opinions. |
Considering Nelson has freely participated and contributed schematics on the Lightspeed thread over on DIYAudio, I'd have to say he must feel this is a pretty good design and it certainly got his attention (as it has other designers of note). Problem with most Pass/First Watt amps is they are not ideally suited to passive designs due to their low input impedance (this is obviously why Nelson designed the First Watt B1 buffer and Pass Labs markets an active line of preamps). Here's a good read from Nelson: http://firstwatt.com/articles.html Click on the B1 Buffer Preamp link. Seems Nelson reiterates a few things we've been saying around here about ideal conditions (impedance matching) and offers his method and design to avoid that. Here's an excerpt: So here we are in the New Millennium, and thanks to Tom Holman and THX we’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more. I especially like the use of the terms "just musical perfection", "really - I'm being serious here", and "reacting psychologically" in the article to emphasize some very interesting points (and all of this of course coming from a genius). |
I agree with Paul. I have found George to be very passionate about what he is doing. I don't necessarily think he is the best communicator (and he has admitted such to me), and he can go overboard at times, but I think I know enough about people and their personalities to see that George just might be a little rough around the edges and that translates into a failure to communicate that can rub people the wrong way. In many ways he reminds me of Audiogon member Rauliruegas. Raul is one of the most passionate people I know when it comes to analog, and his participation in threads while well intentioned, can definitely alienate some people. Some of the same adjectives applied to George have been applied to Raul, and then some. On a personal level my dealings with both of these members have been educational and each has helped me with increasing the enjoyment of my system through their advice and in George's case, his LSA. Sometimes you need to peel back the onion and get down into the other layers. I'd love to head down under to visit George and quaff a few beers with him. His personality reminds me of some of my blue collars buddies from back East. |
One correction to Agear's very interesting post. The Truth is an active buffer, not a passive. To answer his question, I am not a betting man but in a blind test between the Truth and LSA I would bet I could pick them out. This is not to say my hearing is that good, it is to say I have spent so much time listening to these two preamps that I know them that well. Each do a couple of things really well that my test tracks would allow me to pick the correct preamp. Now if I were not as familiar with them then all bets are off. I would probably have a difficult time picking them out. It took me quite a while to figure out the nuances of each unit when comparing them. Pubul57 - I tested the LSA against the Audio Consulting Silver Rock. It was evident that the LSA just got out of the way of the music, like it didn't even exist. In some ways it was a similar experience to something Himiguel wrote in an earlier post here. It was like I could hear the Silver Rock's signature, whatever was causing it to have one. The LSA was obviously the more neutral and truer (purer) preamp. |
This is also very important. An active preamp will be needed if the amp's voltage need is higher then the source's output voltage. I used to think this too until I tried my LSA with my Atma-Sphere S-30. Source = 2V and S-30 = 2.8V - nearly 6V depending on how it was configured. In either case the source did just fine driving the amp via the LSA. |
33k ohm output impedance is rather high, especially given that the Concert Fidelity amps have an input impedance of 47k ohms. Is that 33k ohm constant or at a specific frequency or perhaps a range? Now I know Masa Tsuda personally and have been working the Concert Fidelity rooms at the last few CES/RMAF shows. I'm here to tell you Masa in my opinion is a great designer and the system of components he brings to the shows has incredible synergy and sound. I'm having a hard time getting my hands around this so I'm going to go straight to the source and find out more information. |
George, yes I saw that review and was aware of the other information. As I stated in my previous post, amps input impedance is 47k ohms. What I am having a difficult time with is why the designer would build a preamp circuit with 33k ohm output impedance (assuming this is accurate) to mate with amps that have not much more relative to input impedance. It makes little sense given I have spent approximately 150 hours or so listening to this system and it in no way sounds like a bad match to me. |
Just ran into this thread. Seems another LDR attenuator has been making the rounds as a DIY kit. There is a balanced version available as well. Not sure technology wise what the differences are with the LSA, but thought some of you here might be curious to read about it anyway: http://www.diyaudio.com/forums/vendors-bazaar/176847-warpspeed-optocoupler-volume-control.html |
I have just received some information regarding the output impedance of the Concert Fidelity CF-080 that should put the discussion to rest. According to the designer, the 33k ohm output impedance is an incorrect assumption. In addition to the tubes, the circuit design uses a capacitor and a resistor at the output to prevent harmful DC signal to be transmitted to the power amp. So the actual measured output impedance, which depends on the frequency of the CF-080, is between 5.2k ohms and 900 ohms as measured between various points within a frequency range of 20Hz to 20kHz. From this I would say that the CF-080 will match up just fine with most power amps out there. This includes the Concert Fidelity amps with 47k ohms input impedance. Not that this was ever in doubt from my perspective having heard the system multiple times and regarding it as one of the best I have heard. I fully trust this information as it came from the designer himself. As such I don't feel there should be further debate on the subject. |
George, You, I, and your tube gurus will just have to agree to disagree on this one. I think there could be more to this than we know and if so it may give you and some of the tube gurus the information needed to fully understand the circuit design. However, I'm not going to waste Masa Tsuda's time on this any longer given that he is not prone to be part of a public debate. Suffice it to say as I have stated before I believe Masa Tsuda's specifications for output impedance and can verify that from my own personal use of the CF-080 the tube sockets hold the tube pins tightly and there is no reason for concern that they would fall out. The purpose of the roll bars is to protect the tubes from being banged up against something. I consider both you and Masa very competent designers who have different approaches to achieving specified goals for your respective products. Each of you also have very different personalities. Like I said in a previous thread, what we probably have is a failure to communicate. It's obvious your personality rubs some people the wrong way. For me, that is not an issue, I can handle that. Others, well we know how they react. I agree that one in particular would like to see this thread go away and their behavior shows it. Enough said on that subject. You have been very generous with sharing your ideas and helping people like me learn about a new product that has enhanced my system. Masa Tsuda has done that as well, and in the process become a friend. Like I also said before, if I ever get down under I would certainly enjoy quaffing a few beers with you. Let's get this thread back on course and continue the discussion on the LSA. Also I'd like to discuss this Warpspeed if you are inclined. Seems like another interesting approach. |
If Teajay asked that of Paul I certainly missed it too. Not sure why it's even logical to ask of either of us. In any case I have no business relationship with George. I'm not attempting to design and sell tube amps, I am actually doing it, preamps too, and step-up transformers for MC cartridges. How that factors in here I'm really not sure. However, per Audiogon rules I disclose my business affiliations when required. |
In the system I have that features the LSA my speaker cables are 18' long. The brand is OCOS. They are made by Dynaudio and are known for their performance in long runs. I use 1m interconnects. As for capacitance on the interconnects. Anything under 60pF/ft. should be fine. I'd venture to say you could go higher if you use 1/2m cables. There are a lot of fine cables out there that meet these requirements. The best method, if it is possible, is to place the passive volume control at the amps input. Ralph offers this option on the Atma-Sphere line for the M-60 series on up. However, given the design of the LSA, I do not believe it would be feasible to place it at an amps input. I am curious though if the LSA can be hardwired from source through amp. |
In most cases high end roll off is the symptom. As we age, typically our high frequency hearing regresses anyway. You're not that old though, not that I could tell anyway. Maybe you just find the sound pleasing, for whatever reason, as I did when I used the LSA with an amp with 21k ohm input impedance. Sometimes we take these ratios and such to an Nth degree when in reality maybe it doesn't make as much difference as we think. |
I read that as well and find #4 interesting. Wasn't the whole idea of using LDRs and optocouplers in George's design to take the switch out of the equation. In other words a $5 switch would work just as well as a $200 switch. Regarding #1, this is true in my system, but not sure what the point is. It doesn't degrade the sound. As for #3 I guess by virtue of the fact that the Warpspeed uses a SLA battery, the designer must feel battery power is better. While I liked using a battery power supply with my LSA, I can't say it was better, just a little different, but I could never really pin point why. I now use the battery PS on one of my LSA's and the linear PS on the other. So for me clarification on #2 and #5 would be helpful. |
True, I can't see what more can be done to the circuit. I think George already addressed that going from MkI to MkII. I think we can forget about any upgrade in ergonomics for the time being. Reading about the Warpspeed I find the designer has this thing he calls a Squid in the circuit, but I think it is commonly known as the VCCS. IIRC an idea he got from Nelson Pass. I'm a little fuzzy on that though. Maybe George can clarify. |
Banquo363, have you tried the cheater plug on the RM-10? How loud is the hum? If you have to put your ear to the driver it is okay, but if you can hear it standing in front of your speaker or further away then maybe you should talk to Roger about it. In my system I do not get any hum at all from the RM-10 or EM-7 V12. When adding the LSA and shorting the inputs did you check for noise at various volume levels? The phono stage is more complicated. If a cheater plug did not work try running a ground wire from your phonostage to another ground point, maybe the center screw on the nearest outlet. Any possibility it could also be your phono cable or cartridge wires? |
Banquo363, regarding the RM-10, perhaps some DC on your AC line if you can hear the hum at the amp. It doesn't take much. When I lived in a tri-plex in CA if my neighbor used her hair drier or turned on her window unit AC I would get similar symptoms to what you are describing. Unfortunately dedicated lines were not an option for me. To really isolate the problems after you begin plugging other components into the amp you should get a set of the Jensen plugs. One of the better investments I have made. Also, I won't advise you to do this, but in my system I float all but one of the grounds. Definitely on all my sources, then either ground the preamp, or ground the amp, but not both. The RM-10 manual discusses this too as I'm sure you know. The K&K phonostage, along with the Hagerman Trumpet were two of the best phonostages I have owned. The K&K was the quieter of the too. In general it is a very quiet phonostage due to the solid state PS and input. The newer versions are supposed to be better and I'm seriously thinking about revisiting it. |
I never liked those Rothwell attenuators. You can accomplish the same thing by adding a resistor in series with your interconnects (there might be a little more to it, but this is the basic idea). I believe Luminous Audio makes cables like this upon request. Since you are cutting up some cables now might be a good time to consider doing it. |
Stereophile had a booth at RMAF and I picked up a copy of the November issue because my digital source, the Resolution Audio Cantata (disclaimer: I'm a Resolution Audio dealer), made the cover and was being reviewed. Low and behold though, Sam's Corner had a nice piece on active versus passive preamps and some comparisons between a few of them including a new player from Japan). One quote stood out and was even spotlighted: "The best purely passive attenuator I've come across is the George Hi-Fi Lightspeed." Guess Sam still has a soft spot in his heart for the LSA. Although he is flirting with the new Conrad-Johnson active linestage. |
With the Luxman amp you might want to try the Dodd Audio tube buffer. It gets quite a bit of praise from those who have tried it. In fact, there are some really nice solid state buffers out there as well, namely the Pass B1 and the Horn Shoppe Truth (which uses a photo optocoupler). Buffers are similar to passives in that they generally will not add gain to the signal path, but they also eliminate impedance mismatches. |
Do you have the TRL modded Sony 900? If so you might want to check with Paul to see about the impedance. I had one for a bit that was modded by TRL. This is a solid state player so output impedance should not be that high. However, since it is also SACD/DVD and has a lot of other functions not relevant to 2 channel audio the impedance could be higher. I recall the manual being pretty daunting so it might be hard to pin this down. Why don't you give it a whirl and see. I don't place as much value on the impedance matching criteria that is talked about around here as much as I used to. I've used the LSA with some pretty interesting combinations and it's worked fine each time. However, the one thing I haven't tried yet is a high output impedance source. That will happen after CES/THE SHOW with a tube phonostage I'm auditioning. |
If 10k is the minimum load the Sony is comfortable seeing and the input impedance of the LSA is 10k, then I assume this could work out. My Sony 900 also had the video outputs removed as well and the battery power supply. I think I had the remote too. When the Sony 900 mod was introduced by TRL about 5 or 6 years ago there were about a half dozen of these players available in SoCal that I snapped up for Paul. They were modding them up and the players were going out the door like hotcakes. I think it may be their best effort with a digital player. |
Next generation LSA or another opportunist copycat? Neither. The designs are more different than the same. Not even an evolution IMO. All the research I've done says users who've had both prefer the Warspeed and that this one is pretty much the best of the bunch. Curious to hear why as well, though. Everyone is entitled to an opinion. I have both units and can say the LSA is clearly the purist and smoothest sounding of the two. My reason for buying the Warpspeed is that the builder makes a balanced version which I wanted to try with my Otari reel to reel. It does the job, but it's not the final answer for me in this application. |
Hi George, no I have two dual mono versions. The other one you sold to my friend here locally is also dual mono. So unfortunately I cannot make a comparison, unless of course Pubul57 wants to lend me his for a bit, that is if he can live without it in his system:) I can't imagine why one would sound better than the other. As you stated the switches are out of the signal path. Maybe the ability to dial in the right and left channel volume separately improves the listening experience, from my perspective this is why I prefer dual mono and it does contribute to my enjoyment of the music. However, I could not see this improving the sonic characteristics or tonal quality of the sound itself. |
The Atlas monoblock is 3.1V to full power so I'm assuming Bill has the stereo version which is 2.3V. That should pose no issues for the LSA IMO. The gain stage in the amp is tube driven. Output stage would appear to be solid state. The amp does double its power output from 8 to 4 ohms and it has an output impedance that is incredibly low and somewhat of a norm for solid state. I am curious how Jim White gets such a low output impedance from a zero feedback design. While the LSA does match up well with the Atmas-Sphere S-30 in my system, I do feel it matches up better with the Music Reference amps I have. Driving the S-30 direct from my Resolution Audio Cantata (5.5V buffered output) seems to offer some benefits as well, but it is not as pure a signal transfer. In fact nothing has been as pure as the LSA in my system. If you go to Devilboy's system page he comments on the fact that he did not do a head to head comparison between the Tap-X and LSA. In my direct comparisons with my Slagle DIY unit and the LSA they are pretty close, but I give a slight edge to the LSA, again it is more pure where there is some coloration from the autoformers. |
Hasn't made the website yet, but working on it. We need to officially dress one up and get pictures of it. Similar concept to the Decware CSP as the output voltage is adjustable, but we've added another feature that allows you to set up the output of the preamp using meters on the front panel. So when adjusting the output voltage so you can actually see how you are affecting the sound. If you want a hotter sound you can have that, something a bit mellower you can have that too. Tubes are mounted on the back panel so the preamp has a slim look to it. |
The input sensitivity and input impedance of your amp are fine. The input impedance is 47k ohm which is at the lower end of what the LSA likes to see but will be just fine as I've used mine with lower. The output voltage of your Rega DAC is fine too. What we don't know is the output impedance of the DAc but given that it is a solid state output it should be under 200 ohms so you will be fine IMO. Give it a listen. |