Re batteries vs. wall-warts, perhaps the reported sonic differences are due to voltage differences? I realize that the Lightspeed contains an internal 5V regulator, but perhaps differences in the "12V" input voltage result in different internal operating temperatures, perhaps affecting sonics in some way.
Also, as a point of information, lead-acid batteries (such as the one Anthony linked to), exhibit much greater changes in output voltage as a function of charge state than lithium-ion batteries do.
Best regards,
-- Al |
Is there a Lithium battery supply you would recommend? |
Is there a Lithium battery supply you would recommend? I don't see any reason why the one George linked to above wouldn't be a good choice. Best regards, -- Al |
Thanks, I missed that. I assume it comes with a Global power plug that would work here as it comes from Australia. |
Good point. The prongs which can be seen peeking out in the photo of the charger kind of look like it's probably USA-compatible. And the three adapter plugs it pictures further down the page are obviously not for the USA, which would seem to imply that the built-in plug is USA-compatible. George, can you confirm that?
Also, a number of Hong Kong sellers offer similar battery assemblies on eBay, indicating that they are supplied with whatever plug type corresponds to the buyer's country. Search under "12V Li-ion Rechargeable Battery CCTV."
Best regards,
-- Al |
|
No the battery linked to on my site is the Portable Power 750. You would be looking for the Portable Power 950. |
I ordered 2 Lithium battery supply on ebay, Item number: 190459066434, recommended by George when I ordered my LSA. It's only $13.45 shipped from HK and I too prefer it over the wall-wart for the same un-describable reasons :-) |
A warning from George on a DIY forum:
Got 5 x fakes from these guys in Hong Kong " buyincoins_au " the batteries were ok but all the chargers blew up and fried on 240v or 110v after 15mins of charging time LETHAL!!!
12V DC Rechargeable Li-ion Battery for CCTV Cam 1800mAh (eBay item 190459066434 end time 19-Jan-11 17:50:02 AEDST) : Electronics
The weight to send all back cost more than the purchase, thankfully I did a Paypal claim in time and they refunded me.
Cheers George |
Yeah, I bought one from " buyincoins_au " and the charger never worked or if it did it didn't work for long. The battery itself works fine though. Been using it for a couple of months with a different plug I had lying about. |
Yikes!!! Thanks for the info Pubul57. Mine works fine so far but will keep an eye on it while charging from now on.
Maybe there was a bad batch of chargers ... |
for the same price, or less, (~$395 shipped), i would strongly recommend the diyparadise eva-2 ldr attenuator - this sucker actually improved my sound, (i use an active preamp), by enabling me to run the (already wery transparent) melos tube potentiometer in my highly modded ma333r wide open. the eva-2 is the real deal, imo... 3 remote-control inputs, remote wolume... and yes - ldr
http://diyparadise.com/shop/index.php?main_page=index&cPath=18
http://diyparadise.com/shop/images/P1012169.JPG
doug s. |
At the DIY Audio LSA forum http://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp-391.html
the EVA is mentioned. Here are some comments from George. I've neve heard the EVA so can't comment one way or another. It would be nice to have multiple inputs and remote, but then it might not sound the same....
"And there's where your HF noise is comming from, a dirty switch mode power supply.
And from a high res photo of the guts I was sent by an anonymous sender, they don't use Silonex NSL32SR2S's, it's a far cheaper one so they can max out on profits, and to boot they have input and output mini relays in it, this is the exact reason for the Lightspeed Attenuator, "it's to get rid of all contacts between the source and poweramp" not add more contacts, no wonder it does not sound as good.
But it does look cute, with remote and digital readout, this will attract the naive customers.
Cheers George"
__________________ |
From a customer who has both the Lightspeed and Eva II
----- Original Message -----
From: Sirot Seta
To: George Stancheff
Sent: Thursday, December 23, 2010 4:32 PM
George,
The lightspeed is great and is "light" years ahead of diyparadise's EVA II.
It is much quieter and linearity is perfect.
BTW I wrote a review of a DAC and did mention the use of the Lightspeed, just FYI.
http://www.digitalaudioblog.com/2010/12/review-db-audio-labs-tranquility-dac.html
Regards,
S
Cheers George |
Congratulations George, the Lightspeed pre/attenuator is just magic.
When I was a little boy I had the opportunity to listen to a RCA horn record player (His Master’s Voice) and I was intrigued and fascinated to hear music from it. Many years later I had the opportunity to witness the launch of the CD when I was working for Philips (Chile). The sound quality was impressive compared to the records and the impact to the guests was so big that the audience got up applauding the music. Today I offer my applause to you; the difference in listening to CD’s throughout the Lightspeed and other preamps or just the volume control, reminds me of the experience I had of the difference between vinyl and CD.
Congratulations. |
Okay, dumb question. I have an Arte Form i-150 integrated amp with dual light speed attenuators in it. What does that mean? Is that different that what this thread is about or is it just a type of attenuator that can be put into any preamp or integrated? |
Kcloone,
I believe it does have some form of LDR controlled volume in the new version with lcd readout on the front. I did ask Norman the owner of Arte Forma Audio to remove all references to Lightspeed Attenuator which he kindly did, he now calls his ldr volume the Nature Audio Light Sensor Volume Module.
I have no idea if it is my old MkI version, easy for manufacturers and much cheaper to implement into an amp.
I don't think it's the far better sounding MkII version as this would not be a stable environment for it, as the heat inside would change up to 20c at times inside an amp, and the MkII Lightspeed would go in and out of calibration, it could not be listened to without changing balance calibration every 10 mins.
Cheers George |
Sorry Kclone,
I was a little wrong with the models, it's not the amp but his new $2500usd preamp that has the Nature Audio Light Sensor Volume Module in it to be released in March.
Cheers George |
|
yes, that is the integrated I have, I'm sitting in front of it right now. :) |
Thank you for your appraisal and the pat on the back Brislander.
As you have now experienced the no contacts in the signal path sound of the Lightspeed Attenuator, it will be difficult to go back to an active preamp with a normal pot, as I maintain all pots are flawed because of their lightweight wiper contact (diode effect), that's why they all sound different.
Cheers George |
So why the heck would he false advertise if he really didn't have the light speeds? There has been info on the net about the new version that said they would have them. Heck I bought one, it sounded good to me(no pun). Don't get me wrong I'm happy with the sound of the integrated, but I guess it doesn't really have the light speeds? oh well. |
Even if it is a MkI Lightspeed setup and not MkII in those little boxes, they will still sound better than any industrie standard volume pot you can get.
I asked him to remove all references to the Lightspeed name because it's the name of my product, and he was trying to capitalize on the name that's all.
Cheers George |
Quick question: would the LSA's full potential be realized in this setup: PS Audio DLIII ( 99 ohms Z out ); low capacitance one meter interconnects; aragon 8002 power amp ( 22k Z in). Speakers spendor s3e. Average listening level : low to medium 85 db ish... I use a buffered passive in same system. Volume range is more than adequate. Somewhat concerned about lowish input impedance of amp...thanks. |
I'm sure it uses LDR technology. Question is how is it implemented and what parts are being used. Hard to tell as you can't see inside the boxes. By virtue of the fact that Norman previously used the phrase Lightspeed to describe his volume control, do we really know if he is using the same LDR's as George. Since George has made his design and schematic public it's quite possible, but I haven't seen anything that describes exactly what Norman is doing.
BTW - I'm pretty impressed with the build of the unit. A couple years back I remember seeing some tube designs from Arte Forma here for sale. They were beautiful units and again appeared to be well constructed. Then they disappeared. Seems like they are back now with a US distributor. Hope they reintroduce the tube amps I previously saw. |
Yeah, for a sound quality standpoint, the Arte Forma integrated is very good. Sounds way better than it's price point, that is for sure. |
I'd be concerned about the 22k input impedance of the Aragon as well. Maybe George could elaborate more, but I'd say it probably would not work optimally. |
Dpac996, sounds like a setup where a TVC/AVC/buffered passive would work best than an LSA or Placette RVC type passive. Still might work pretty darn well, so worth testing if you can, but on paper it does seem less than optimal given the input impedance of the amp. How much off optimal? Don't know. |
Yes the Aragon's 22k is the problem you would need a buffer after the Lightspeed, but if your handy or know someone who is you could change the 22k input resistor to say 82k.
If the input of the Aragon is fet then all will be fine with the 82k. But if it is bi-polar then the Aragon may give out bit of dc offset with the 82k if switched on with nothing connected to it's input. (just make sure the Lightspeed or something else is always connected)
Cheers George |
Hi George. Thanks for the suggestion. Somewhere I have the schematic for the 8002. Ill take a look. Have you considered creating potted drop-in attenuators so that folks could upgrade their current preamps if so desired? For instance say I have found excellent synergy with amp/speaker but the amp is not remotely passive friendly...or another scenario: I have more than one source to switch? Im thinking that your volume control would ( if pot resistance compatible) be a marked improvement as a replacement for existing traditional pots. In a similar twist any thougts on designing a tube output buffer with your ldr attenuator? |
The best sounding discrete buffer I have made is a tube buffer called the "SLCF" (Super Linear Cathode Follower). It was first use as the output buffer in the top of thie line Tektronics Ocilloscope, it has the lowest ouptut impedance of any tube buffer, under 100ohms. But it still does'nt sound as good as no buffer.
http://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp-364.html#post2346943
Cheers George |
Is the use of a transformer/autoformer or buffer in a passive the same? Are they just different ways of lowering the output impedance of the preamp, or is there some other function that distinguishes xformers from buffers? |
Hi Paul,
Yes, there are significant differences.
An active buffer stage will provide a gain very close to 1, while providing a high input impedance (to the stage itself) and a low output impedance.
A transformer or autoformer will transform impedances in proportion to the square of the turns ratio that is selected, while at the same time causing a voltage reduction (or gain) proportional to that turns ratio. Example:
If a TVC is set to provide 12db of attenuation, that corresponds to providing an output voltage that is 1/4 of the input voltage. So the turns ratio for that setting would be 0.25. The output impedance would be ((0.25)squared) or 1/16th of the output impedance of the source component. The load impedance seen by the source component would be 16 times the input impedance of the destination component (presumably the amplifier).
If the TVC were set for unity gain (no attenuation), there would be no impedance transformation, the output impedance would equal that of the source component, and the input impedance would equal that of the destination component. But as the amount of attenuation is increased, the output impedance will decrease rapidly, since it is proportional to the turns ratio squared.
Best regards,
-- Al |
|
Just wanted to weigh in on using a Lightspeed in very unfavorable impedance conditions. I have a DAC with an output Z of 10k and an amp with an input Z of 15K . All logic tells you that inserting the Lightspeed between those two devices would spell certain sonic disaster. I had resigned myself to using an active preamp until I could solve the impedance mismatch either by using a buffer or replacing equipment. My active tube Preamp is an Airtight with an input Z of 100K and an output of 600 Ohms easily fulfilling the "10 to 1" rule.
Having already pulled the Lightspeed out of the system knowing it could never work anywhere near as optimally as my expensive tube preamp , I suddenly decided to compare the Lightspeed to the Airtight. With only one input it was a simple swap and within the first 30 seconds I realized that the Lightspeed even in a terrible sub optimal impedance match was wiping the floor with my active preamp ANYWAY. Just thought I would give more than a sliver of hope to those who think the Lightspeed won't kick your expensive active preamp to the curb even in a bad impedance mismatch. Yes George warns over and over that the Amp "should be over 50K input Z" and the source "should be 200 ohms".
The last thing I ever expected was to hear the Lightspeed be more dynamic , more extended, more spacious and 3D and to basically make a very very fine and expensive preamp sound absolutely woolly by comparison and all this in what was supposed to be a very impedance unfriendly situation. Now all I want is to do is stop slapping Ohms Law in the Face and try to get the impedance matches where they belong so I can hear the Lightspeed in its full singing glory. I can't even imagine how much better it could be , but I will sure try to get the matches right and let the Lightspeed cut loose.
SO , for a quick recap, Just because your impedences don't fall in the 10 to 1 rule or better, don't think the Lightspeed won't easily dethrone your expensive active preamp anyway and make what you thought was the best Preamp you ever heard sound broken by comparison. |
Funny, I've been considering trying an Airtight of late. Guess I'll cross that off my list.
I have used the LSA as well with unfavorable impedance matching. Into am amp with 21k input impedance. It did sound good, although you will definitely hear the difference when using it with optimal impedance.
The "10 to 1" rule is overrated IMO. |
Another one bites the dust:) |
As I see it the 10:1 rule will be of no importance if all of the following conditions are satisfied:
1)The output and input impedances that are involved are both essentially resistive, and do not vary significantly as a function of frequency. That condition will usually not be satisfied if the preamp has a coupling capacitor in series with its output, as is the case with most tube preamps and some ss preamps. I'm uncertain as to how often it will or won't be satisfied if no capacitor is present.
2)The component supplying the signal can handle the load impedance without distortion or other signs of stress. I would not expect that to be a problem in most cases unless the load impedance is very low (e.g., 1K or less).
3)The loss in gain that will result is not an issue. For instance, a 1:1 ratio would result in a 6db loss in the maximum volume that can be achieved, in comparison to a high ratio.
Also, cable capacitance must not be too high in relation to output impedance, but that is a separate issue.
BTW, if the Air Tight's 600 ohm output impedance specification does not make any reference to frequency, and if the design includes a coupling capacitor at its output, the output impedance is likely to rise to considerably greater values at very low frequencies (perhaps 3K or 4K at 20Hz). With a 15K load impedance, that would result in a small but very conceivably audible bottom octave rolloff. A nominal (presumably mid-frequency) output impedance number should be multiplied by 50 to 75x, rather than 10x, to be completely safe under all circumstances, IMO. The 10x number would be appropriate to use if the worst case output impedance is known.
Regards,
-- Al |
I'm sure I asked this earlier, but can't find my question or the answer - can the LSA be built as a balanced output, if so, any serious advantage to that with let's say an Atma-sphere amp? |
Yes you did ask. I've gone down this road with George. Bottom line he gave me the schematic, but warned that overall this is an inferior design due to the difficulty in matching the additional LDRs (versus single ended operation). In addition, if you can get one built there could be a higher probability of reliability issues, again due the higher number of LDRs to achieve balanced operation.
That being said I recall Audiogon member Dave Garrettson trying to match LDRs for balanced operation to use as a volume control internal to his Atma-Sphere MP-3. He gave up on the effort IIRC. There have been a few people on DIYAudio who have tried to build a balanced unit. I didn't sound like it was a lot of fun.
You really should try it single ended into the M-60 amps. You're going to be really surprised. I get the balanced thing, especially with Atma-Sphere components due to their supporting the 600 ohm standard, but the LSA is quite optimal with these amps too. |
But I have so many NOS stocked away for my MP-3:) |
There is a market for those NOS tubes;) |
Lstack, thanks for the write up on the Lightspeed Attenuator in a system that was not a prefect impedance match as this has never been done before. I have listened to it in the same situation and thought it was still better than listening to active pre's and other passives, and this is what I tell customers when they ask.
It's just not functioning at 100% of it's capabilities, so when you do manage to listen to it properly matched up you will only then realize it's full potential.
BTW there is no problem using it this way, no harm is done to anything.
Cheers George |
Al, as you might know, I am very non-technical, so I had to read what you wrote a few times. Is it correct to say that
A transformer replaces resistors as the means of attenuating the signal and provides some impedance matching help.
Buffers attenuate nothing, but creat ideal impedance matching. |
Paul -- Yes, that is exactly correct IMO.
Although some might raise minor quibbles about the use of the word "ideal," because there will always be a limit to how severe a load a given buffer can handle without its performance degrading.
Best regards,
-- Al |
Forget "ideal" - didn't mean to say that, but I think you know how I did mean it. |
Fellow Lighspeed owners - The listening level that I use has my Lightspeed volume at about 8-9 o'clock as my 97dB efficient speakers don't require many watts to crank them up (I'm using an Art Audio PX25 SET amp with 6watts/ch. by the way).
Am I missing anything by not having the volume at a higher setting (11-1 o'clock for example)? Besides getting louder, will the sonics improve as I turn the volume up louder?
Thanks! |
George is the expert and I'm sure he will give you the definitive answer, but I think I read somewhere that LDRs work a little different and that I'm not sure it actually improves as you get further into the rotation as is normal with most attenuators. George? Al? Anthony? |
A couple things. One, the sensitivity of your amp is quite low, 770mV (and if you have the 350mV option extremely low). The input impedance is a very compatible 180k ohm. I looked at your system page and was wondering if you are using the Metric Halo LIO-8 as your source. I did look at the specs of that piece and the output impedance is quite low at 5 ohms, which is compatible with the LSA. The spec I couldn't find is the output voltage of the unit. What I did find was:
Maximum I/O Levels (Balanced)
Peak Line Output @ 0 dBFS (no jumper/low power) +18.5 dBu
Peak Line Output @ 0 dBFS (output jumper/low power) +22.0 dBu
Peak Line Output @ 0 dBFS (output jumper/high power) +24.5 dBu
Analog Send Max Output +21.5 dBu
Line In Max Input +24.5 dBu
Output Impedance 5 Ω
Monitor Controller
Nominal FS output (Balanced) Output Jumper Off -19.0 dBu
Nominal FS output (Balanced) Output Jumper On -12.0 dBu
Maximum Output Same as Line
Gain Range -96 dB to +30 dB
Gain Precision ±0.05 dB
Gain Step 0.5 dB
I'm kind of curious of what the effect of the peak line output and gain range are all about. It's a bit foreign to me but this is a pro audio unit so it appears they are stating things a bit differently. Could be too much output from the source and it doesn't take a whole lot to drive your amp to full output.
The LSA doesn't have the same mood swings as your typical resistor based passive, but it doesn't maintain the same output impedance across the volume control. The big thing in your favor is the 180k input impedance of your amp. You are likely to be well above acceptable ratios no matter where you are on the volume control. I think worse case scenario is the output impedance of the LSA is around 8k ohm, so you have a very good cushion given the high input impedance of the amp. It would be nice to have a bit more flexibility before you hit your desired volume level, but I don't think you are missing anything at the level you're at. |
Kevinzoe
Am I missing anything by not having the volume at a higher setting (11-1 o'clock for example)? Besides getting louder, will the sonics improve as I turn the volume up louder?Kevinzoe
Unless you have very high capacitive interconnects (more than 200pf per foot) you will not hear a difference, even with 200pf per foot = 600pf for 1mt, the -3db point will be at 38khz at the worst position (highest output impednace) of the Lightspeed output impedance.
If you use better interconnects 100pf per foot = 300pf per mt, the -3db point will be at 76khz.
I use interconnects that are 40pf per foot = 120pf per mt, this with the Lightspeed is -3db at 190khz. and so on.
Cheers George |
