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 think it is patented, in fact I think George has already nixed one such attempt of using his design commercially without permission - but George could speak to that.
What I did was to stop someone else from trying to patent it a couple of years back, what they wanted was for audiophiles to think it was their idea, but my first one was made back in 1974, using t/t and phono stages as the source, but they were not very reliable with the ldr's back then, lots of channel drift, and no led's I had to use low voltage bulbs. This was when I should have put a patent on it. As for now just the TM of the name Lightspeed Attenuator will suffice. And the small ego boost that the IP was mine all those 37 years ago (yikes!!!!). I believe as the manufacturing technology gets better they will be able to supply the Silonex led/ldr packages as perfect matched quad sets for stereo use and you will see the demise of the potentiometer with it's lightweight internal touch contact of a metal wiper on a carbon track , as they are the weakest link in the audio chain. Cheers George
I have a question regarding the relationship between a cd player's output impedance and the input impedance of the Lightspeed. I have read the cd or dac should have an output impedance of 200 ohms or lower. This seems to be needed even if all the other hurdles are met.
I have a cd player with 2 volts of output, but the only spec I can find on Impedance reads " load impedance over 10 kilohms". Not sure if this is suggesting the output impedance is 10,000 ohms! Does not seem possible!?
The unit is a Sony dvp ns900v sacd player. I purchased the LS for a second system and to just play with.
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.
I just looked at the manual and it appears the audio output and 5.1 channel output are both listed at over 10k ohms. Not sure what more I can say at this point. The high output impedance is unusual for a solid state player but my guess is that is due to it being a DVD player as well as CD/SACD.
Happy new year to you all, the 10kohm load impedance that Sony and some other are are saying about their output, is the minimum load that this output would be comfortable (mathematically) seeing. Not it's output impedance. The only way to determin what the output impedance of it is, is to load the output to ground with different resistors unlit a 1k sine wave is halved in level, what ever that resistor is is also the output impedance of the unit as you have formed a voltage divider with the resistor to ground with the output impedance(resistance) of the unit. Cheers George
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.
For Sony to quote that this unit should see 10kohm or higher as the load, says to me that one, it could be tube output (which it's not), or that it has a 1k series output resitor (which is dumb to do), or that it maybe have a capacitor coupled output to stop any dc offset at switch on, or just when it's on, to stop it from taking out amps and speakers. Trouble is with is, some of todays amps at 2k or even 1k input impedance that capacitor would have to be 200uf odd to get the frequency response down to -3db @ 1hz, and a cheap bi-polar or plastic at those values could have very high ESR (series resistance) whch could be adding to the problem of not being able to take loads of less than 10kohms.
"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."
and
"I could be wrong, but from what i've read it sounds like the Warpspeed LDR is the newest type of LDR to come to market. The Lightspeed is an older design. "
Yes, it would be good to hear from someone who has actually owned both, or auditioned both at length? Anyone on Audiogon? You?
As far as I know, the LDRs themselves are identical, but Alan appears to have tried to address some ergonomic issues, a more complicated device it seems. Sometimes a tradeoff, especially with an approach principled on simplicity and minimum of parts, contacts, etc. Would not mind trying a WS to see, but not many available, and I certainly could never make one for myself from a kit.
It's all good to add fancy ways of not having to quad match the LDR's but the end result is there's more junk in the signal path and it results in differing sound qualities (not levels) at different listening levels for each channel. This below is what I posted at DIY about the same subject.
"You need to look and measure that the I/O impedances of both channels at differing levels remain the same to each other, if not and they have different values of Z in and out (i/o), this will effect the sound quality of each channel hence may/will effect the stereo imaging. It will simulate the same effect as having large different lengths of interconnects for each L and R channel. That is why quad matched sets have a consistency between channels, they remain equal for both at all levels of listening, unlike some of the pseudo Lightspeed Attenuators that are comming thick and fast. There is no free lunch."
As you noted earlier in my question about an improved version, it seems that after 30 years of tinkering, the LSA is well sorted out, and at some point there is little to improve, without as you say paying a sonic cost in the service of some other goal. To me, the only issues are stability over time, and balance control - which unfortunately requires dual volume controls for best sonic results.
Dual L&R volume controls are the only option I provide for the Lightspeed Attenuator. It is the only one that does not effect the sound quality, though as you can imagine it is slightly more difficult to use, but a boon to those who have unsymetrical systems or room acoustics.
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.
Agear, seems like your have you answer. The "latest" is syrup thrown on the original and the greatest. But if you still have issues, buy both and decide for yourself; the LSA is still the gold standard, even though it might not be the "latest" -- hard to improve upon perfection. If you personally find something better, do let us know, but you are up against a tough audience of folks who enjoy the LSA. Have you actually used it? Doesn't seem like it.
I just saw the Warspeed thread on AC and was mildly curious. They could not provide any details on "why" it was better, and it simply seemed like a me-too product. The name even tells you as much. From the listening tests mentioned earlier in this thread, the battery seems to have no sonic consequences.
IMO, George deserves all the credit for this development. It is his intellectual perseverance that has made it possible, and any "new" developments are to be viewed with a jaundiced eye.
I would also like to hear other opinions about this from owners. This is what I found, I have Lithium Ion batteries I use, and no one, even "golden ears" who visit can reliably detect the difference between them and the standard mains supply that comes with the production Lightspeed Attenuator, and this is on a very high rez system. Even Sam Tellig "golden ears from Stereophile" said the same, as he bought the Lithium Ion batteries as well for his Lightspeed thinking they had to be better (pure dc and all) than the regulated mains but no he said if there is a difference it's miniscule and not detectable.
I wouldn't say the battery option improves the sound, but there is something different about the sound when using the battery power supply. I just can't put my finger on it. I go back and forth between the two.
Because all the supply has to do be it battery or mains, is to hold the LED Light (light emitting diode)steady at a predetermined (by you) luminosity level between 1 and 20mA, this LED in turn shines on the LDR (light dependant resistor)which changes the level of resistance needed to change the volume of the source to the poweramp. As you can now see the power supply has no electrical contact with the LDR or signal. And the led is gas (no filament) so it is impervious to vibrations or shocks.
Given George's comment, it would seem the burden of proof is on explaining a difference, not the other way around. I find Clio9's comment interesting, as he does hear a difference, but even there hard to put your finger on it, also hard to measure the influence of expectation on something so subtle. However it may be, going to battery supply just doesn't seem like a path with pursuing, at least not to me.
If you know LED lights, you would know they are an extremly stable (even thermally) form of light being powered by battery or regualted mains. This is maybe why battery cannot be picked from regulated mains in an A/B comparisions, like I have conducted many times with fellow audiophiles, a few said they can detect something but cannot put their finger on what it is.
Perhaps the reason some of you are reporting sonic differences between using battery power and the wall wart is simply that volume levels haven't been precisely equalized for the comparison?
I realize that the LSA has an internal regulator, but no regulator is perfect, and so perhaps voltage differences between the outputs of the battery and the wall wart result in slight (fraction of a db) changes in attenuation, that need to be compensated for with the volume control.
To totally rule out the possibility that the sonic differences are attributable to volume changes, I believe that the levels should ideally be equalized to within around 0.1 db, which is probably impossible to do without instruments.
Anthony, no, I was assuming in my last post that both supplies are nominally 12VDC. However, neither is likely to be exactly 12VDC, and the two are not likely to be exactly the same. Also, the output voltage of the battery will change slightly as it discharges.
While the significance of those differences will be greatly reduced by the internal voltage regulator, as I said no regulator is perfect. So it seems conceivable to me that if the power source is changed but the volume control setting is not changed, there could be a tiny change in volume that would be subjectively perceived as a sonic difference.
Sorry guys the internal regulator in the Lightspeed Attenuator is 5v and will be the same regulator regarless of using battery or mains, so ther is no difference in voltage that the LED's are seeing not even a miniscule of a volt. Cheers George
So taking any power differences to the LED's out of the equation all we have left is noise difference of battery v mains. But if anyone can hear the difference between 6uV and 4uV they must be superman. I have measured this my Tektronix scope which has very good low resolution. When the shorted input Lightspeed was powered by the battery I measured a noise floor of close to 4uV (that's microvolts not millivolts) When it was powered by the mains it was then 6uV. These are exceptional figures as most things in audio are measured in mV (millivolts) which is 1000 x higher than microvolts. And so it should be this quiet as it is passive and has no noise of it's own. But if this is perceived difference some hear (as I also hear) between battery v mains comes down to those miniscule noise differences then the book has to be re-written.
Given George's good answer about noise level, and his answer implying that the "line regulation" performance of the internal 5V regulator is good enough to reduce expectable variations in the 12V input to the point that they would not result in a perceptible volume change (which is certainly do-able in a quality design), I'm out of ideas as to what could account for sonic differences between battery and wall wart power (assuming that the wall wart being used is a linear supply, not a switching supply).
In the February issue of TAS, Neil Gader interviews John McDonald of Audience, and he said something that somehow seems related to this thread:
"At Audience,the Golden Rule is 'first, do no harm,' defining harm as any deviation to the original recording. So high-end to me and to the Audience team is about staying true to the music. Sound-sculpting should be left to the recording artists and engineers"
He could have very well had said, "true to the source" - which I suppose is one reason that those that do like the LSA, like it - true to the source is the raison-d'etre [?] of the hair shirt minimalist approach to do no harm.
You find can many synonyms for the golden rule of audio used by manufacturers and end users alike. It makes for good ad copy. The problem is how you define "source". If by source you mean the recording, then unfortunately 9/10, the harm has already been done. One of the primary "sound sculpting" tools used by recording engineers seems to be compression. The rectification of that and other sins committed in the recording studio makes this hobby a lot more arduous than it should be.
For the sake of clarification, I am referring primarily to digital source material as I am a child of digital revolution.
When I say source,I mean the recording, not the live event -there simply is no direct connection to it, but the recording is the reference for purposes of the argument here - true to the recording is proabably better language than saying true the source (live event) - that simply is out of our control and always lost in the very processing of recording, no matter how good the recording and playback equipment. I feel like in a Platonic cave all of sudden....
All you proud Lightspeed Attenuator owners, look out for the upcoming Stereophile issue (I think April issue which comes out in March) with Recommended Components listing, as they just emailed me for any changes (pricing, design etc) to be included in the write up on it. This will be the 5th time your Lightspeed Attenuator has made it into Recommended Components since 2009 when Sam Telling first bought his from me. I have a feeling it may set some sort of record for Recommended Component longevity.
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