Good to hear Dpac996.
In your quest to sample a buffer after it, even though I believe the best buffer is no buffer so long as the impedance boxes are ticked for passive use.
If you want to try an simple good stable at unity gain opamp buffer, the most transparent/dynamic one I have come across in my experiments with I/V stages and buffer stages for cdp's is the AD825, the OPA627 is a tad cleaner but it doesn't have the dynamics of the AD825 and dynamics = rhythm and pace.
Cheers George |
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 |
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 |
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.
Cheers George |
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.
Cheers George |
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.
Cheers George |
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.
Cheers George |
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.
Cheers George |
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.
Cheers George |
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.
Cheers George |
Maybe one day in the future, fancier glitzier chassis, remote control volume, multiple inputs (switched via wetted relays). It will more than treble the price but still sound the same, no better than the original sounds now. And some complain about the $500 shipped worldwide cost of the current unit, go figure what they'll say when it's $1500+ for the fancier one.
Cheers George |
220v/240v wall warts are supplied to most countries except the U.S. which is unfortunately 110v. (Just like you guys also drive on the wrong side of the road compared to everyone else).
I refund $15 to those customers and give them a few links to get their own in the U.S. on line.
In Australia it is a safety issue to sell or supply or import 110v wall warts, on suppliers sell them, as you can imagine if one were to be given 240v it would become a molten mass very quickly.
Cheers George |
From what has been told to me OPC271 (one of the first Lightspeed copies) is like my original Mk 1 Lightspeed Attenuator but with more glitz, which is a series resistor and shunt ldr, while it was still sounding very good and better than all other volume control devices on the market, is not as good as the MKII Lightspeed Attenuator which is series LDR and shunt LDR, which has a lower low volume and more stable input and output impedances, and the main difference it sounds far better, especially in the bass and dynamically.
This is why all the MK1 Lightspeed Attenuators were recalled and converted to MKII status and were well praised by their customers.
I wish I could have continued to make just the MKI as it is far easier to manufacture as the MKII is exponentially harder and expensive to do.
Cheers George |
Their shunt LDR could be paralleled by other shorting components, as there is no way of getting -99db of attenuation any other way, not even with best NSL32SR2S's which have the lowest on resistance of 60ohms at 20mA in quad matched form, sure you can push them to 25-30mA to get 30ohms but then they will fail after time.
Cheers George |
Yes rooms can be a problem, I have a very symmetrical room but about 1/3 along the side wall is a 1 x .7 mt glass fronted photo and it has to have a towel put over it when I do serious listening as the sonic hf mf side reflections it produces does tend to shift the imaging around a little, maybe this is what the customers who are in favour of the dual mono Lightspeed Attenuators model are hearing when they say they like it better.
Cheers George |
Hi Paul, the dual mono version is $35 more than the standard stereo version at $490 (which is not backwards compatible) and this includes worldwide shipping.
Yes you can use the same wall wart, if you already have this then there will be a price adjustment of $15.
Cheers George |
Sorry, should of explained it better.
If you have a stereo version it cannot be made into a dual mono easily, as the chassis parts are drilled/mounted slightly different and circuit boards are done/wired different to accommodate the dual setup. Even though electrically circuit wise they are almost identical save for 2 extra led controler hook ups.
Cheers George |
Clio09, Tony hi, wonder if you can confirm something for me. As I think you have purchased both stereo and dual mono Lightspeeds from memory, as I have never had the opportunity to do it and it goes against all logical reasoning.
I have had a few report from customers that have the dual mono (left & right volume led brightness controls) Lightspeed Attenuators that they have done comparisons with friends that have the single stereo control Lightspeeds and they believe that the dual mono sounds a little bit better, this goes against all logic for me as the only difference is that the dual stereo pot is split into two mono pots all values and circuits are the same and as all probably know they only control the led brightness and have nothing to do with the ldr signal component.
Cheers George |
Marqmike: Yes you can do that, I have one customer in Hawaii that bought 2 units off me years ago, thinking he wanted the extra one for a friend. He thought he needed 2 for stereo then found out when he got them he only needed one.
I said for him to send them both back and I would give him a dual mono instead and refund him the difference, he kept both and to this day is using both as you have outlined.
Cheers George |
This is possible Paul, but thermal inter-channel drift is only prevalent in DIY Lightspeeds or Lightspeed clones.
The production Lightspeed Attenuator that have been built by us, all have their quad matched NSL32SR2S led/ldr units packed together. Then they are potted together in hard wax, this keeps them thermally stable to each other and ensures the final calibration to remain correct for years.
My prototype has now been going (powered) for 6 years 24/7 and is still in calibration after all this time, and I have never had one back just for recalibration.
Cheers George |
Clio09 I am curious how Jim White gets such a low output impedance from a zero feedback design.Clio09
Could be that it has no "global" negative feedback, there are such things as "local" feedbacks, and even feedforward circuits. It all in the wording.
Cheers George |
Just in case some are wondering, Tristone (Lei) ordered a dual mono unit, these seem to be gaining popularity as it gives audiophiles a balance control being separate left and right volume controls.
I still recommend the stereo unit if your room and system are balanced from left to right, as dual mono can be a little less user friendly to use, as the famous Audible Illusions 3A's used to be if you ever lived with one.
I know some her have built their own Lightspeed clone from the circuit boards that are available on DIY forum, so I have posted up how to modify the circuit board for dual mono use should you wish to do it. Here is the link.
http://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp-443.html#post2944737
BTW Tristone thanks for the rap!!
Cheers George |
Hi Gooddomino, what is the model number of your Rega Dac.
Cheers George |
I had to look at the Stereophile review of the Rega Dac to find out. It's the only place I could find what it is, even the Rega site doesn't say. They (Stereophile) measured it at 620ohm, strange this is quite high for a solid state output I wonder if it's correct, email rega direct and ask.
But it should pose no problem if it is to your setup, just keep your interconnect short and low capacitance.
Cheers George |
Any cable that is below around 150pf (picofarad) per foot is considered to be low capacitance.
This is a specification that should be advertised with all cables bought on the packaging.
A manfacturer worth his salt should be able to tell you what his cable measures if you email them, if not stay away from that cable.
Cheers George |
Hi Kevin, the distortion that the NSL32SR2S LDR's is .02%. This is also 2HD the nice one that tube amps and preamps give, but in a low feedback SE tube amp case this can be much higher at up to 2%. So as you can see .02% is nothing and it's the nice tube sounding one.
Also I saw that quote and it is also based I think using the Vactrol ldr which are inferior to the Silonex NSL32SR2S for both distortions and impedances.
Cheers George |
Hi fellow audiophiles, first off let me thank you Paul for starting up a Lightspeed Attenuator thread as writings about it were so scattered amongst the other non descript threads, it would have looked sus if I had started it.
I have a simple website at www.lightspeedattenuator.com and you can also access it via the Audiogon manufacturers listings.
If any of you would like a PDF sales/pricing/shipping brochure you can pm me via this forum with your email address and I will send it to you.
Cheers George |
The Morrison Elad is just a normal active preamp using normal pot and a 50 cent Analog Devices AD797 opamp with no gain.
It has nothing what so ever in similarity to the Lightspeed Attenuator and it has nothing what so ever to do with LDR's or LED's.
Cheers George |
Faziod Hi you will hear very low level of music at minimum level as this is the characteristic of ldr's in this design is they can never go to complete darkness or infinite brightness as these are the controlling factors for resistance. Think of it as there is no such thing as infinite brightness or infinite darkness.
Cheers George |
For members who wish to know how I started the Lightspeed Attenuator project, a small portion of the history is available on this Audiogon post.
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1275616047
Cheers George |
Tompoodie
Also, is anyone aware of a mechanical switching box that would allow one to have, say, 3 rca inputs and one output.
There are many out there here is one. This is the best way as it will still allow you go direct when you want the best out of the Lightspeed.
My prototype has two inputs with the best switch you can get and it is still bettered by every single input production Lightspeed I listen to before shipping out.
http://www.mcmelectronics.com/product/DISTRIBUTED-BY-MCM-INP-3-/50-6170
Cheers George |
I would guess nearly 99% of good quality cdp dacs have an output voltage of 2v (Redbook Standard) or higher and an output impedance of 200ohms or lower.
Amps may have a input impedance of 47K (industry standard) or higher, nearly all tube amps are 100k or higher and an sensitivity of 1v or higher to clip.
So 2v feeding 1v to clip? no preamplfication needed here
200ohm or lower output into 47000ohm? no impedance mismatch here either.
So if a active preamp tube or transistor sounds better in the above "common" situation it is as Paul says giving the owner the tonal quality they want to hear (less bass more bass) you get the picture.
This however a band-aid fix for that system by throwing in a costly preamp to fix a system problem and at the same time missing out on all the transparency dynamics and sweetness that no active pre can give. Would it not be the wise thing to do and fix system imbalance (different interconnects speaker cable and positioning) problem instead of throwing a costly band-aid at it?
Cheers George
|
Grannyring
I have a gaint in my opinion :-)
Good on you Grannyring you've given me my laugh for the day, I'm just a tech with limited English skills I had to look up "gaint" this is what I found in the Urban Dictionary
gaint: loss of blood to the brain due to overly large erection.
Cheers George |
Sorry to hear that Paul, (please no hate mail) your in good company though, a customer a while ago just sold his $18000aud Matisse Reference pre because of the Lightspeed Attenuator, he invited me around for a listen, it looked ridiculous, here was the diminutive Lightspeed wired up to these 4 x box (coffee table sized) Jadis Reference monoblocks. Boy did it sound good though into the top Avalon speakers.
Cheers George |
06-16-10:
Grannyring:I have a question for you owners of this exciting volume pot. Will it work well on speakers that are 87 db efficient like Soundlab speakers and other ESL's? I say this assuming the amps are very powerful and the spec criteria mentioned by the poster are meet by the source unit and amps.Grannyring:
My Martin Logan Monoliths ESL's are around 86db, I am never more than 11 o'clock for very very loud listening. I make it a point of asking customers with low efficiency speaker where the position of the volume control is for good loud level listening, and the worst was 82db speakers and he was still only at 1 to 2 o'clock for loud listening sessions.
You can gauge this for your self by putting your source directly into your poweramps to see if is loud enough for you, I bet not one person says they need more level even with 82db speakers and this is what the Lightspeed Attenuator will let through no more only less if you turn down the volume control.
:This next part is important to read:
There is no need with todays high output sources (cdp,dacs,phono stages) the need to preamplify, they have enough output to clip nearly all poweramps into any speaker on the market. So why would you want to amplify again (with a preamp)only to knock it back down again to below the original source output???.
Cheers George |
Banquo363
This warm up period with vinyl, it's probably cold/stiff cartridge suspension to start as they are made of rubber then it get's more malleable as it's used this could be the reason.
Cheers George |
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 |
06-16-10: Pubul57
No, thinking more in terms of power delivery and power supply fluctuations, the ability of the output stage of the CD player to drive the ICs and the amp
There should never ever be powersupply fluctuations in the output of a cd player, if there was it needs to go to the recycling tip.
As for the power delivery, (which means current delivery) If your source (cdp) has a low enough output impedance (say less than 200ohms) and it sees an input impedance (load) higher than this there is no current delivery problem, it's only if it sees a input impedance (load) lower than 200ohm then you can start to have current limiting.
Output impedance of the source has to be lower than the input impedance of the next stage, this goes from cdp to pre, then from pre to amps, and then from amps to speakers. And don't forget all interconnects and speaker cabling have some resistance this should be added to the input impedance of the load, this is why one should not use hair thin cabling as it has more resistance and adds the load resistance.
There endth the "Ohms Law" lesson for today need to build some more Lightspeed Attenuators, will back later.
Cheers George |
I use Express 6 MkII interconnect by Eichmann but I don't wire it like they do, I put all reds together and all backs together I found this sounded better and was more electrically logical, the way they had it was strange and sounded that way.
I also like it because it is substantial have 6 solid core individual conductors of about .5mm each 3 red 3 black individually insulated the encased in a blue gel type outer sleeve with no shielding at all, as I have found shielding can increase capacitance/inductance.
Also I like that is pure 99.99%ofc copper, I have never liked silver or silver coated, I find it artificially accentuates the highs, giving a false impression of detail while robbing body from the lower-mids and leaning out the bass.
Then for speaker cable the same Express 6 MkII speaker but its twice as thick probably 1mm conductors
Back to work
Cheers George |
Grannyring
Ok, one last question. If I run my CD player right into my amps, won't that damage the amps or speakers? When this is done will my system play at full volume? Half volume? I can't image playing at full volume as I never go past 1/3 or so right now - to loud!Grannyring
This is why you MUST pick a known quite starting CD like the lead in for an orchestral piece so you can gauge the level. This is a test to show you what the source (CDP) without preamp colourations/distortions sounds like.
You don't hope into a Ferrari for the first time and put the peddle to the floor, you would do it gently at first, then kill yourself when the testosterone takes over.
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***@earthlink.net 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 |
Clipsal
I also would like to know the poweramp used in this shootout and also the CDP or DAC.
Cheers George |
Who cried "foul"??? All that was questioned was the the load the Lightspeed Attenuator was seeing into the Samson amp to see if it was working at it's optimum, it is you have tured it into something else.
Cheers George |
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 |
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 |
Darkmoebius
As we all know, it is almost impossible to know which component is "true" and others are additive, or subtractive(except for truly bad components), unless one was present for the actual recording session. As to knowing what is the "true" amount of soundstage width or depth on a myriad of recordings, I think that would be an impossible task.
In reality, any preamplification is probably "truest" if it helps bring the listener a deep emotional connection to their music within the context of that listener's musical preferences and system/room acoustics. Nothing else should matter, in the end. Darkmoebius
Thought I'd chime in on this one being the manufacturer of the "Lightspeed Attenuator".
Hi Darkmoebius, welcome to the discussion, you used the magic word "truest" twice in the above reply. Having not yet heard one for yourself, can I make a suggestion to get the "truest" idea of what pre/amp passive or active is "truthful" to the original recording.
Plug your CD player or dac directly into your poweramp "this will be a perfect impedance match" As you have no volume control, first off play something that is low in level to gauge how loud it will be, doing this you are playing the "truest" form of cd/dac playback you can possibly get. Then slip the Lightspeed or any other pre active or passive back in adjust for the same level, and you will see and hear which one is "truest" to the source.
Cheers George |
From what we have learnt and heard for myself, the only way to make all interconnects invisible (sound the same) with no sonic signature, is to have the poweramp input impedance at 1kohm or less, this then becomes a hard load for the pre to drive unless it has an output impedance of close to 1ohm and plenty of current behind it, something like the top Krell pre amps may be that low, then the pre itself has a sonic signature itself, so it's not an easy task.
Cheers George
|
09-09-10: Darkmoebius But, it did pose a problem playing vinyl w/ low output cartridges. I needed the extra gain of an active preamp or a phono pre with a lot more gain.
Darkmoebius
Strange? I have lots of Lightspeed Attenuator customers that use vinyl with low output moving coil cartriges, all they have is a good phono-stage like the Tom Evans and then Lightspeed Attenuator directly into their poweramps, and they are at 12o'clock on the Lightspeed for good loud level, with plenty headroom left in reserve, they say it the best they have ever heard their vinyl sound.
Cheers George |
