I've been using the LSA with a Spectron Musician for the past couple of months and I'm very very pleased with the results.
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.
1,866 responses Add your response
Teajay asked me that? That's odd - missed it. I use to think this site was mostly enthusiasts that liked blabbering to each other, but perhaps there are more commercial interests lurking in the woods that I care to think - nothing wrong with that if there is full disclosure. As far as SS, I never tried it, and unless it was a 100kohm impedance load, I proabaly would not bother, something like the First Watt Alpeh J might do well, but for the most part, I see this as a tube amp device, though I imagine it has been used with SS and like Drubin some of them have found it perfectly suitable. Disclosure: I paid full price for my LSA. |
Don't mean to suggest with an amp with less than 100kohm input impedance, rather that would be my personal pridelection - I'm sure Goerge would point out that 47kohm and up should work fine. Of course you would not have any tubes in the chain and I would only use a SS amp with a tube preamp - something always seems to be missing when there are no tubes involved - I don't like it nearly as much. |
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. |
I have had my LS now for over 2 years and can thoroughly recommend it for its clear, transparent sound. I use both integrates and pre- amps and since buying the LS, my favourite pre being the Melody 1688 has sat in its box due to non use. I sometimes tend to have short listening sessions and warming up a tube pre is inconvenient. The LS having only one set of inputs hasnt been a hassle as I use a multiple input phono stage but when I do need to change source say to CD its a little hassle unpluging and repluging new interconnects. For the price differential compared to a full blown multi source pre that sounds as good, its not a hassle at all. George, if you made a dual/multi source LS then the world would be your oyster! cheers Michael |
I've been using my lsa with ss monoblocks. In the beginning the lsa was polite, missing some dynamics. But I have changed the whole thing, other cables (shorter and different brand), I have modified a bit the poweramps (by somebody, a wizard). The lsa "sounds" terrific now! Dynamics? Yes! Polite? No way. All in all te lsa "sounds" as it should be, no other (?) preamp in the 15k pricerange (and maybe above) comes in the neighbourhood imho. But George could you make a remote control.....? batalok. |
I've owned one for years since i first saw it reviewed in 'audiophile'. It performs flawlessly and i would suggest less is more in these preamp circumstances. I have also owned the 'promethius' pre-amp and found that volume attenuators do a great job. If you must have an expensive pre-amp because you trust your wallet more than your ears then so be it. But if you can afford a very epxensive pre-amp, then trying out this little $470 number as an experiment won't hurt the purse strings. |
I have been using the LSA for a few months now with Coincident Frankensteins. It replaced the Coincident Statement linestage which I really loved. I was lucky to reach out to Tony (clio09) when I saw he lived in the same town. I heard it in his system and for $470.00 decided to give it a try. As others have said it is flawless and is like having a direct connection from source to amps. I do have a system that meets the requirements- short interconnects etc. I have no problem with those that love active preamps, but for this price I think everyone should try the LSA. Thanks Tony! George |
09-27-11: Acuscott "...if you can afford a very epxensive pre-amp, then trying out this little $470 number as an experiment won't hurt the purse strings." Precisely. It is indusputably worth auditioning and deciding for yourself if it does the trick in your setup - you may be more than pleasantly surprised. |
Grannyring: I've noticed a great dependence on cable length. Because of my set up, I have been running 2m Mogami cables out of the LSA to my rm10 and 1/2m Soundsilver sextopia into the LSA from my Allnic phonostage. They are both low capacitance so I thought I'd be ok. Bored last week, so I moved the LSA closer to the amp so I could use the shorter cable (I used the longer cable to connect stage to LSA). Big difference! For the better, I think, but that's besides the point. I've now purchased longer speaker cables so I can try short IC's for both the input and output. |
My record for misspellings in a single comment. George, is there any issue other than capacitance related to cable length? That is, would a 1/2 meter of a quality cable almost always sound better than 1 meter even if it were slightly more capacitive; is something going on with length other than aggregate capacitance? Are any of these differences even relevant a 1 meter or less of IC? |
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. |
The HF filter that capacitance of an interconnect that is 300pf for it's total length when with the Lightspeed is 76khz -3db 200pf is 114khz -3db and for 100pf it is 227.5khz -3db. As you can see even the 300pf is fine as it is still only -3db at 76khz. This is why I recommend 100pf max per foot and the use of 1mt length with that maximum capacitance. But most good quality interconnects are well below 100pf per foot which is even better. This also applies to high output impedance tube preamps with their interconnects, especially when say a 30kohm output impedance preamp is used, if it has an interconnect with 300pf for it's length, it works out to be -3db at 17.5khz which cuts into the audio band quite severely. Cheers George |
Banquo363 The 1.2kohm for the phono is very high and should not be an "ideal" match with the Lightspeed, but it will not be harmful to anything either. I have quite a few customer with dac's and phono stages with output impedances this high with tube output, and they say they couldn't care if it's not a 100% match as they are over the moon with the sound that they are getting with them into the Lightspeed Attenuator. Cheers George |
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. |
Banquo363Am I right in believing that non-ideal impedance match between phono stage and LSA results in a attenuation of the high end? Perhaps it hasn't bothered me because of my old ears?Banquo363 No, the slight impedance (resistance)mismatch you have will compress slightly the dynamics, and if ever the output impedance becomes higher than the input impedance then you will attenuate the whole signal, as it then becomes a voltage divider. What attenuates the highs is lots of cable capacitance. Cheers George |
09-28-11: Banquo363Not necessarily. It depends on how the two impedances vary as a function of frequency. If neither varies significantly over the frequency range, there would be no adverse effects, just a slight gain reduction. I couldn't find any indications of the output impedance vs. frequency characteristics of your Allnic H-1200, but more often than not the most significant output impedance variation of a tube-type line-level component will be an impedance rise at deep bass frequencies, due to the output coupling capacitor that is commonly used. That would cause deep bass frequencies to be attenuated, assuming the input impedance of the destination component is reasonably flat as a function of frequency. What will attenuate high frequencies is a combination of high output impedance (at high frequencies) plus high cable capacitance (or, in theory, high input capacitance of the destination component, but that generally doesn't occur in practice, and I assume does not occur with the LSA). Regards, -- Al |
I bought a Lightspeed about a year back. It works really well with both the PSAudio DL-III and PWD. It lets a lot of the more subtle details come thru, and with less edginess. Please note that you need a low-output-impedance source and a high-input-impedance amp to really take advantage of the LS. Both of the PSAudios have 100 ohm outputs, and my amp has 220k ohm inputs with 20dB of gain. Altogether, given the impedance and gain issues, the LS is certainly worth auditioning. That it costs less than $500 makes it a no-brainer. |
George, in the Warpspeed DIY thread, the poster identified some area we he thought the LSA could be improved: What I found interesting at the start of the Warpspeed thread was the identification of a few "problems" with the LSA and attempt to improve upon the LSA: 1. the inability to adjust to complete silence 2. on low/high volume level settings, power levels on the LEDs endanger/shorten/toast the life out of the optocouplers 3. the need to improve the power delivery to the optocouplers 4. the need to improve on quality of the volume adjustment pot 5. the Lightspeed, simple as it is, still has a number of variables/design factors that affect performance What is your view on these issues. On 5, we wonder if perfomance can be improved or you feel that after 30 years of sorting this thing out we are pretty much at the performance limit - obviously some ergonomic issues exists, but might not be addressable without compromising ulitmate performance. |
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. |
2: Never had any problems with the ldr side, as my prototype is still as it was when new and that's 7 years now powered 24/7. When I say in the instructions to leave the Lightspeed Attenuator at 1/2 volume when leaving it powered up and not listening, it's the led's I'm thinking of, even though when at full or min volume they are never at their max mA rating, it is in my opinion to share the use evenly so I say leave it at half way if not in use (listening). 5: The best is as it is now, it's simplicity in it's purest form, as the music signal only goes through one soldered resistor (ldr) from input to output, anything else would need to go through more devices. As for the power to drive the led's, it is known that battery is the purest form of dc power, and so many times we have A/B'ed between the wall wart and a Lithium Ion battery and nobody could detect the difference reliably some say they hear a difference but can't tell what it is. Even golden eared Sam Tellig, need to see with his own eyes if he has the wall wart or battery attached to his Lightspeed when he's listening. As for the Warpspeed not interested in it, too much other crap being put into the signal path. As for doing any other things to the Lightspeed, I would like to have more inputs, but the only way I would do them is to use Mercury Wetted relays for the input switching (which I believe are being made illegal) and that would be still not as good as only one input with no switching. So use one of these, and then you can still go direct when your really want to hear your system at it's best. http://www.decware.com/newsite/rotary.htm The only thing I may do in the future if I find a reliable set is a remote control volume and I would make sure it's retrofittable to all older Lightspeeds. But I have not yet seen a system I'm happy with that has long term reliable supply and quality. For a remote volume you need, a quality remote, receiver circuit, motorized pot and power supply to run it and the receiver Cheers George |
I don't know what it is (thanks Almarg for the explanation above), but I've been switching my short (1.5 ft) and long (3ft) interconnects as described above and I always get better sound when the short IC is between LSA and rm-10. Perhaps it's as Almarg noted: that there's an attenuation of bass due to variations in the impedance of my tubed phono stage. At any rate, I now get more dynamic and better bass (articulate and rich). I get 15-20db dynamic swings (as measured by my radio shack meter) on symphonic music, from the average sound level to peaks. Not bad at alI, I think. What counts as a good dynamic swing? Joe Morello's drum whacks can now sound like a shot in the dark. I've made a myriad of changes to my system of late and I'm continually impressed by how the LSA allows me to note them all, good and bad. I guess that it's the LSA's neutrality 'at work'. Thanks, Clio09 for the shorting plugs idea above. I made some and went through the procedure. My rm-10 is not dead quiet, close but not quite. Transformer hum, I believe. But the LSA with shorting plugs adds no additionally noise. My phono stage however...There's a dreaded ground loop I think. I bought a cheater plug but that didn't help. Mercifully it's not too loud. I need to have the LSA at 3 o'clock to be bothered by it at my seat. On a side note for those using the rm-10: I've been using NOS GE El-84's and they're fantastic. Superior to the stock tubes and to the Genelex reissues. |
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? |
Clio09: with shorting plugs, I had to put my ears to the speakers to hear the hum AND buzz on the rm10. However, I just tried it again and now I get dead silence. ??? There is a hum emanating from the transformer when I'm near the amp. It varies in its loudness depending on the fullness of the moon :). I thought until just now that that hum was making its way to the speakers--guess not, or not always. Yes, with shorting plugs in the LSA, I get roughly the same level of hum and buzz at all volume levels (well, up to 3 o'clock--I've never turned the volume past that). And it was the same level as the RM-10 with shorting plugs, i.e. very, very low. However, today, with the amp dead silent, I get the same buzz and hum with the LSA. Once I introduce the phonostage, then the objectionable noise appears. With IC's into the LSA but the stage off, the hum is loud. After I turn on the stage, the hum diminishes greatly and is overtaken by or competes with the tube noise in my stage. At ambient room levels, it is barely audible at my seat with the LSA at 3 o'clock. I very rarely listen at that level so it doesn't affect my music. But being neurotic, it still bugs me. My phono cables are grover huffman's latest. They are supposed to be well shielded. As for lead wires, I swapped out the stock wires on my AT LS-12 headshell with copper litz wires. With everything else going on, it's hard to say what effect that had. I should just sell my stage and get one more compatible with the LSA and quieter. To be honest though, the system sounds great, so I'm hesitant to mess with it. Do you have a K&K stage, Clio? How's that in terms of noise? |
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. |
Hi guys, as I have found out input switching is almost as detrimental to the sound quality as a volume potentiometer, this is why I always recommend a separate good quality input switching unit so you can still go direct when you want to bypass all contacts and get the best out of your system or when you want to show it's transparency off. http://www.decware.com/newsite/rotary.htm Now the obsessed fiddlers on diy audio have found this out also, and to their credit they have now devised their own way of input switching unit using ldr's http://www.diyaudio.com/forums/analog-line-level/197894-ldr-based-input-selection.html I still think the one I posted was simpler and it auto shorted the unused inputs. http://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp-153.html#post1640716 Cheers George |
Clio09: what's a jensen plug? I looked up Jensen 'iso-max' products but there is a legion of them. Which one are you referring to? Is it for diagnosis or treatment? Regarding lifting the ground, the only other item I have with a 3 prong plug is my stage. I use the walwart that George pointed to and it is two pronged. My tt's power supply is also 2 pronged. I tried a cheater plug with the stage and it didn't help. I had entertained the thought that it was the LSA's walwart that might be responsible. But I swapped in a battery supply I have and the same noise persists. I once considered a switcher but I'm over it as well. I use almost exclusively my tt, and swapping IC's is easy because I have an open rack. I can see the appeal though if one had a cabinet and switched sources constantly. I'd be interested in hearing the difference a switcher makes though. Anyone use one? |
There should be only one mains earth point in a system, (if you have more than one you will have a loop), all the other components will get their earth via the interconnects from the one that is earthed. Once you have two components earthed then it will become a loop via the house earth line. Even when I had two monoblock 805 tube SE that I built, I got a virtually no hum when only one was earthed and the other got it's earth via the interconnect to the Lightspeed and back down the other interconnect to the unearth monoblock. PS wonder if I'll get the magic 1,000 post with this as they moderate my posts for up to 6 hours before approval. Cheers George |
Here is what you are looking for: http://www.jensen-transformers.com/isokit1.html In the photo you will see two plugs in the lower left with orange barrels. These can be purchased separately and IIRC are less the $20. They are diagnostic only, but more accurate than shorting plugs at isolating ground loops. Only other reason I can think of for the noise is RFI. Phono stages and tubed ones especially are notorious for picking it up, cables too. |