Lightspeed Attenuators owners and diyer's, I've just been informed again by Stereophile, and you'll be happy to know that your Lightspeed has just made it again into the Recommended Components with the highest 3 x $$$ rating for sound and value for money in the next issue.
You can download it free via Apple Ipod from the Stereophile website or wait for the hard copy to come out.
Cheers George |
Should be no problems, try it on low first you should have enough seeing you have at the moment with it direct. Then if you need to push it harder try the 5v.
As for the impedance of 100kohm on the Krell this is great, as with the Lightspeed which mimics a 10k pot you'll have a combind Krell plus Lightspeed load impedance 9k which the 300ohm source output will see which should also be fine.
Cheers George |
I have tried very very hard to make a Lightspeed MkII balanced and reliable to stay in calibration even with electronic genius's trying to help out, but without some extra electronics (like sampling impedance values sort of feedback) it does have a negative effect on the sound quality, so it is not possible, and it would of put the price through the roof.
My old MkI Lightspeed design is possible to make balanced though, but it does not sound as good as the MkII. So your damed if you do and damed if you don't.
Cheers George |
What I meant is that I would not sacrifice sound quality by going back to the MkI Lightspeed configuration and having to charge more for it because it's balanced. I don't think anyone would expect that, let alone purchase it.
Single ended sounds better if the interconects are kept at a reasonable lenght because of less electronics in the output of the source and input of the amps. If say 10mts or more interconnect is needed then balanced can start to sound better, but the Lightspeed is passive and it cannot drive over 10mts anyway. So we're back to square one again.
Cheers George |
You have no gain worries now then, just flick the gain switch on the back of the Ayon to 5v go direct into the Krell from it and you will have the most transparent/dynamic sound you can get this way, with a bit of gain to spare.
If you find yourself using the Ayon's digital volume too far below 1/3 of full up, then you can order a Lightspeed Attenuator, turn the Ayon full up and have the second most transparent/dynamic sound you can get.
Wished you would of told us all about the Ayons gain switch and that you had it on 2.5v instead of 5v would have saved a lot of research and guess work.
Cheers George |
Wow!! Your guna make me work for it, I'll try my best, in point form.
1: For 1mt anything below 100pf per foot is fine
2: Yes a number of my customers use quality xlr to rca adapters
3: Not much lost with quality adapters from what they say, the gains out weigh the the minuses big time
4: The signal only passes through one special passive fixed resistor that can change it's resistance (re: volume) according to the amount of light shone on it. but the light is control by solid state components.
5: The Lightspeed Attenuator is true to the source, it adds nothing and detracts nothing, it is the most transparent/dynamic way of controlling the volume of the source to the power amp/s. The only way that can be more so is to plug the source directly into your amp, but then you have the problem of no volume control.
6: There is no gain it is unity gain.
Cheers George |
You will not gain anything by putting the Lightspeed into your system and I would'nt sell you one until this is sorted out.
As your Krell FPB700CX has balanced inputs and is 100kohm with 3.58v sensitivity, that is, it takes 3.58v in, to take it to full output just before clipping.
Your Ayon CD2s has balanced output of 300ohm with up to 5v out at full level.
So you can see your Ayon at full volume output has enough output to take your Krell beyond it's full output which will damage it, you have either done this and is the cause of your Krell's damage, or something else is misconscrewed.
Cheers George |
http://reso.no/wp-content/uploads/2012/01/CD2s_5-300x200.jpg |
You are correct Photonman, they are made of extruded aluminium, not sheet metal as you can see in the picture.
lightspeedattenuator.com
Cheers George |
This can be done Nguyen, as it is how I run it, bi-amped, both amps are 100kohm input impedance, Lightspeed sees half, 50kohm, same difference.
The thing to look at is the combined input impedance of your main amp and the subwoofer amp.
If your main amp is say 100kohm and your subwoofer amp is 100kohm then the Lightspeed will see 50kohm again this is fine.
But if your main amp is 100kohm again and your subwoofer amp is 20kohm then the Lightspeed sees 16.6kohm not so good.
Cheers George |
Devilboy, Photonman seems to have found so nice low capacitance ones,
Quote "I am using a 3 ft set of Bryston IC's (Canare and Neutrik) which are 21 pf/ft into the LSA and a 2 ft set of Blue Jean IC's which are 13 pf/ft out of the LSA to amp."
These are very low, I myself have not used Mogami so I can't comment on them, but if they are below <100pf per ft they should be fine, any cable manufacturer worth his salt should know this spec, and they should be made to advertise it in their specs on the packaging.
Cheers George |
You want to keep your total length cable capacitance under 300pF, which most are anyway.
Cable is usually spec'ed by how many pF per foot. So if you have a 3ft/1mt length, you want the cable to be spec'ed at 100pF per foot or less. And most are anyway, except for the rubbish out there.
If the manufacture does the right thing it should be in the specs written on the box, if not he should know it, if he doesn't don't buy it as he has no idea what constitutes good cable design.
Cheers George |
Hi Devilboy, glad your enjoying the Lightspeed with your setup.
There is no problem with the 51k Z of your amp. As we have done extensive A/B listenings tests on a very high rez system with amp input z loads from 300k right down to 33k, and only then did 2 of the 40 Audiophile listeners think they detected a very slight change when we got to 33k.
Just use good qualtiy interconnects from the Lightspeed to the amp/s at 2mt or less.
Cheers George |
I would put the lower one from the Lightspeed to the amp. Saying that what were the pF measurement for what lenghts of the both cables you have? And then I can then give you a -3db HF roll off point in khz.
Cheers George |
I just saw in your previous posts that the capacitance you have is so small on both cables it does not even factor in which goes after the Lightspeed.
As the Blue Jeans at 2ft you have at 13pf per foot will be -3db at 874khz!!!
And the Bryston cable you have at 3ft at 21pf per ft will be -3db at 541khz!!!
As you can see it will not matter as far as the -3db roll off point, just what you prefer the sound of in which position.
Cheers George |
Yes, Photonman it's only when the cheaper cables get over 100pf per ft and a meter (3ft) or more long things can start to happen.
eg: a bad quality high capacitance cable of say 100pf per ft and 1mt long would be -3db at 76khz which still fine but you get the picture.
Cheers George |
You could for comparison against the wall wart use one of those small square Duracell 9v Alkaline batteries, or even a rechargable one, it will probably last for 24hrs.
Just wire up a 2.1mm dc plug to it (but please make sure + positive goes to the centre of the plug)
Anywhere between 9v-18v dc is fine, as inside the Lightspeed Attenuator there is a second regulated supply that regulates everything that comes into the dc socket down to 5vdc.
Cheers George |
I'm very conservative with that statement just in case the interconnect is poor quality high capacitance. I call it like it is and don't try give best possible scenarios only. Here is a simple semi technical explanation.
In your case with 20ft, lets say that the cable is good quality and low capacitance, a nice low capacitance figure would be 10pf per ft, with your 20ft that is total 200pf.
200pf connected to the output of the Lightspeed Attenuator makes a high frequency filter of
-3db at 114khz. No problem as you can see way higher than our best human limit of 20khz
Double that 20ft of cable capacitance to 20pf per ft and the -3db is then at half the above at 57khz still no problem even 20ft of interconnects.
Halve the length to 10ft and then your back to -3db at 114khz way out of the audio band. Halve the capacitance to 10pf and your at -3db at 228khz!!! bat territory
Cheers George |
Just thought you owners of the Lightspeed Attenuator would like to know, that it has made it again into 2013 Octobers Stereophile Recommended Components, with the highest $$$ value rating once more.
Cheers George |
Banquo363 that site takes Payapl, so you will also have it's buyer protection. And I believe their postage is reasonable, and you get to order the right voltage for you country as well.
Cheers George |
If it's a new one, far as being fixed under warranty, ah, yes that would be out the window.
If you decide to do it, do not use the nylon insulating washers that come with rca's. You must make sure that all 4 x of the metal bodies of the new rca's are in electrical contact with the back panel.
And be careful the black anodising on aluminium chassis is an electrical insulator, so leave the burrs of the rca holes sticking up as they contact the rca's body.
Cheers George |
Hi Banquo363, that's great to hear, but I am a bit shocked at the amount of difference you heard. Are you in the US or Canada?
Is it possible the 110v wall wart you have is a SMP (switchmode)?
As I cannot supply 110v wall warts to the US.
I only supply my own linear wall warts to 220-240v countries.
If your 110v wall wart is a smp (switch mode) then this would explain the big difference you heard, as they are very dirty, even though regulated, and can radiate their crap right through the system, even via the air.
Cheers George |
Banquo363, you can tell a smp wall wart a couple of ways.
One is they are half the weight of a linear, but if you don't have a linear to compare it to then that's hard.
The other way is to get an AM radio and go near it tuning up and down the am dial, you will hear it if it's an smp.
Another way is that they have nearly 2 or 3 times the amperage ratings for the same given size of linear wall warts.
Cheers George |
B_limo hi, the smp high frequency rubbish gets into everything even the grounded chassis, interconnects, input and output, even your amps and source can get it via the wiring or even through the air, especially if it's a bad designed one.
The AM radio trick (above) will really give you a big shock about the run of the mill smp wall warts and why the high frequency rubbish is like a cancer for hiend audio.
Cheers George |
Banquo363:
This looks very small, and at 500mA indicates to me it's an smp wall wart.
Cheers George |
Banquo63: I did a quick search, very hard to find linear ones as they never state if it smp.
These are the parameters you should look out for.
1: 9vdc-18vdc linear
2: can be regulated or unregulated as the Lightspeed Attenuator has it's own internal 5v regulator.
3: 200mA or higher
4: plug has to be centre positive and 2.1mm x 5.5mm.
I quickly found these in the US via a Google search.
http://www.jameco.com/1/1/51493-adp2108gt-2-1-9v-dc-unregulated-wall-transformer.html
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_null_2192712_-1
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_null_2197484_-1
And these from Part Express, but they don't say if they are smp or linear.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=120-1055
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=120-1100
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=120-1095
Cheers George |
oops just noticed, the first Jameco one may not be linear |
Lacee hi, are you in the US also, just wondering if your wall wart was smp or linear?
Cheers George |
B_limo
George,Another quick question: would the lightspeed attenuator work well with a prima luna prologue five tube amp?
Input impedance 100 kohm
input sensitivity 600 mv (the man. site said 600mv on one page, 775mv on another...)Thanks in advance, George!
Perfect match! and just about any source will give out more than 600mV. Most give 2000mV (2v) or more.
Cheers George |
Lacee: also if in doubt if your wall wart was linear or smp.
Try to find a portable AM radio and with it tuned off station low down on the dial frequency with the volume up go near to your powered up wall wart with it.
You will hear very clearling if it's smp as you get closer to it with the radio.
Cheers George |
John47
I supply 220v-240v linear wall warts to the rest of the world. US and Canadian owners purchase their own 110v ones from within North America. Who knows what they are getting from their suppliers, as linear wall warts are getting very hard to find, smp is the norm now.
You need not worry John47 being from New Zealand I would have sent a linear to you.
Cheers George |
I believe the Teradac power supply (http://www.ab-system.hk/index.php?route=product/product&path=73&product_id=64 ) is a great linear power supply. And at a good price.
But from the Lightspeed owners in the US and Canada that have said it's far better than the wall wart, we really need to know if it was an SMP wall wart, they were comparing to. It is very hard to tell the difference visually between an SMP or Linear wall wart. The portable AM radio trick is the easiest way to tell.
Cheers George |
Lacee hi, first off I'll explain the Lightspeed Attenuator consumes around 50mA max, "you could almost power it by rubbing two sticks together".
A 300mA wall wart will power 6 x Lightspeeds. So it's not a question of power, thicker wires or getting more current to the Lightspeed.
It noise, and smp wall warts are noisy little buggers, go near them with an AM portable radio and it will squeal like a stuffed pig.
If your wall wart is a linear one then it should be a close comparison to the Teradac (without hearing myself) because a battery is the closest to the perfect power for the Lightspeed, and not many people can hear much difference from battery to a linear wall wart.
However a smp wall wart is rubbish for the Lightspeed, I've even seen the difference on the test bench. These smp wall warts will be bettered by a Teradac and or battery by a long way.
Cheers George |
John47
That is unless you had your own wall wart, and just ordered the Lightspeed without wall wart, I had a few who've done this.
Cheers George |
Hi Lacee, I like the Teradac, that's why I posted it up for Lightspeed owners to try, as we are always wanting to try out different things.
An smp wall wart will not give noise that you can hear, but it can be seen on the ocilloscope as very high frequency rubbish, and it gets through every thing in the system. What this does to the sound is anyones guess.
What I want to get down too is if the Teradac power supply was compared to a smp wall wart or linear. So far no one has been able to say without question.
Cheers George |
01-15-14:
B_limo: George, two questions: does the lightspeed ever need to be recalibrated? It seems like my volume control may be adjusting in larger increments than before...
Question 2: is it okay to dress it up a bit? I was thinking about a small wooden case or having it professionally painted.
B_limo
Q1: Only if any part of the rest of the system has changed with a different gain to it source amp or speakers. As it's impossible for the Lightspeed Attenuator to change gain as it has none.
Q2:As the Lightspeed chassis is part of the RF shielding, puting it into a wooden case may introduce rf noise into the system.I advise against it.
Cheers George |
It would need to be electrically conductive, the only paint I know of that is, is rear window demister paint. Better off lining the whole inside with aluminium foil then it needs to be earthed to all 4 x rca sockets so it gets a system earth. All too much if you ask me, just enclose the Lightspeed as it is with the wood of your choice, that way all is still RF shielded.
Cheers George |
Photonman, good news that you prefer the Teradac, am I reading right that you think it's a little better than the wall wart you have, if so in what way? And do you know if your wall wart was linear or switch mode?
As for Nelson Pass and that buffer. Many thanks to him as he first developed it for the Lightspeed Attenuator back in 2008 so that it could then drive some of his amps that had low input impedance that customers owned who wanted to use the Lightspeed with it. Those amps for memory had around 10 or 20kohm input impedance.
Here is the link to the 2008 post and circuit diagram for the Lightspeed he developed.
http://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp-137.html#post1521766
http://www.diyaudio.com/forums/attachments/analog-line-level/109114d1211904694-lightspeed-attenuator-new-passive-preamp-atten-sch.jpg
Cheers George |
Audiolabyrinth, I tried, but couldn't find the thread, which forum is it in?
Cheers George |
Found it and answered.
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1392847679&&&/Pre-amp-or-cd-direct-to-XA30-5-
Cheers George |
Audiolabyrinth:
Thanks for the invite, but cables and how they sound are such a subjective thing, and very system dependant.
All I say that for all passives and high output impedance tube preamps, one should make sure that the capacitance of the cable is low, as not to form a HF (high frequency) filter if the capacitance of the cable is too high.
Luckily good quality cables are nearly always low capacitance, and just to be certain you should ask the manufacturer.
A good worst measurement case is 100pf (pico-farad) per foot or lower good ones are much lower, for a 1mt interconnect this worst case capacitance would be 300pf, this equates to with a passive and many tube preamps to have a HF (high frequency roll off at around -3db at 76khz.
But if you pick an quality interconnect that is 50pf per foot, then the HF roll off is -3db at 152khz.
Cheers George |
03-03-14: 4hannons
Drubin, I wouldn't use the Pardo;the 12V/2A will fry it. The LSA takes 1A max I beleive. I'm not an expert, maybe others with more knowledge will chime in here... Sorry but just to correct this, it will work fine, so long as the plug that goes into the Lightspeed Attenuator is 2.1mm and centre positive. Voltage can be between 9vdc-18vdc. True 2amps is way way over kill, but the amperage does'nt matter so long as it's above 100mA. Cheers George |
Yes this what good interconnects should be, as little as possible capacitance.
Otherwise if over 300pf total for a 1mt length, they will start to create 1st order (gradual) HF (high frequency) roll-off's into the audio band when combined with nearly all passive preamps and many of the tube preamps as well.
Giving the impression of sometimes sweeter highs less sibilance (if the system has some).
And because the top end has been curtailed a little less detail, it can also give the impression of more bottom end or richer lower midrange.
Cheers George |
|
04-28-14: Digital3
George will these cables fit the 2.1mm dc connector on the lsa. Yes, the Lightspeed Attenuator has a dc socket that has a 2.1mm centre pin, 5.5mm external, plug. The centre has to be positive which I believe the TeraDac is. Cheers George |
05-19-14: Erwann
The only limitations I can think of, have nothing to do with the sound: leaving the volume control half-way to extend the life of the optoisolators took some getting used to, and indeed the lowest setting lets will let some minimal signal through, which compared to my previous setup, however, is well within my tolerance, and greatly superior to my earlier direct CD to amp connection. The overall experience is far beyond my expectation. This is a product that I will not be parting with, period.
Erwann (Answers | This Thread) Glad you like it so much Erwann, as for leaving it at 12o'clock when not listening, this is not set in stone, as the leds should last 10-20 years at full power, which I never run them at, and by leaving it at half volume should double or tripple this life. PS don't forget to let us know how your $15K!!!! analogue source sounds through it when you get the chance, as analogue lovers have told me it's the best they have ever had their records sound. Cheers George |
05-09-14: Jult52
I compared the LSA with a switch-mode ps and the linear TeraDak 9v supply discussed earlier in this thread. I am going to report a null result: I could not reliably differentiate between the sound of the two. The TeraDak carried no benefits in my system. Hi Julian, I noticed on another forum you did a comparison with the Lightspeed up against another clone, and mentioned the Lightspeed Attenuator had the better bass performance. I believe there could one of 3 factors for this difference. 1: The main one I'm leaning towards may be that the Lightspeed has no contacts in the signal path, where I believe the clone has, as it has input switching. And the whole point of the Lightspeed when I first built the original in the 70's was to eliminate any switches or volume pot wiper contacts from the signal path. 2: I also use quad matched LED/LDR's in the Lightspeed, this keeps the i/o impedances more stable, and also gives a better logarithmic feel to the volume control, I believe the clone only uses 2 x matched pairs. 3: I use the more expensive NSL32SR2S, where the clone from what my spies told me does not. Cheers George |
|
|
That's great to hear Lacee, echoing many of my customers are reporting back to me and say that with the Lightspeed Attenuator as the preamp it's the best they have ever heard their vinyl/phono sound.
I did a bit of searching and found your Steelhead, has a great low 150ohms output impedance. With the Clearaudio Talisman Gold V2 you are using, where is the Lightspeed's volume control when listening to medium loud volume.
Cheers George |
