Yes I believe I remember seeing this unit on SNA, that was 7 months ago hardly recently.
http://www.stereo.net.au/forums/top...tinued-part-6/?do=findComment&comment=1741923
From memory the original owner asked me about repairs or mods before it went up for sale, so this may not be representative of what and how a Lightspeed Attenuator sounds.
Yes please by all means send it to me, I don't want potential faulty units floating around on the used market, it's one way of getting bad press, you have a PM with my address
Cheers George
http://www.stereo.net.au/forums/top...tinued-part-6/?do=findComment&comment=1741923
From memory the original owner asked me about repairs or mods before it went up for sale, so this may not be representative of what and how a Lightspeed Attenuator sounds.
Yes please by all means send it to me, I don't want potential faulty units floating around on the used market, it's one way of getting bad press, you have a PM with my address
Cheers George
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A volume control is not supposed to inject 'life' into a signal, but merely attenuate it while not otherwise harming it. A passive preamp does this. One of George's LDR units will probably do a similar job. Maybe you prefer the 'sound' of the noise and distortion added by some preamps, or your setup requires a genuine buffer (e.g. because of long cables or nonlinear input impedances??Khaleesi said:
While I take no issue with what you experienced - you heard what you heard and didn't like it - I think it's worth noting that the vast majority of the easily 1000+ people who've test driven an LDR based passive come away with a positive experience with most expressing genuine surprise at how good an LDR attenuator sounds.
"Flat, compressed and lifeless" is so far removed from how even the least impressed hands-on user characterizes the "LDR sound" that I suspect that something was amiss with the particular unit you tried. I see where George suspects the same.
Best,
Morten
Late to the party, but I brought a candle
So folks, I think I have an idea of what's going on here with the LDR devices encouraging favorable responses in quite a few listeners. Anyone heard of the pro audio devices designed by Aphex to enhance harmonic content (referred to as Aural Exciters)?
They were used with enormous popularity back in the 1980's and '90's both for final pop and rock mastering, as well as by radio stations to draw and maintain listeners. Essentially they were very subtly designed harmonic generators that had a dynamically responding attribute.
I haven't yet heard an LDR attenuator myself, but wouldn't be surprised if their popularity could be linked to the same psycho-acoustic proclivity for those who enjoy their sound. All the reported benefits line-up with the same subjective responses of the listeners back when A.E.'s were being used regularly.
Perceived increases in "impact", "clarity", "bass response", and "loudness" were fairly common, until the process began to be overused in the initial battles of the "Loudness Wars", which eventually led to their falling out of favor. Utilized with subtlety, however, most listeners would never have perceived the devices' effects consciously, and would simply have preferred the sonic results.
I look forward to obtaining and experimenting with one of these LDR devices when time and budget permits. Maybe even as a gain control element in the negative feedback loop of an op-amp, if it can be used in a stable way.
So folks, I think I have an idea of what's going on here with the LDR devices encouraging favorable responses in quite a few listeners. Anyone heard of the pro audio devices designed by Aphex to enhance harmonic content (referred to as Aural Exciters)?
They were used with enormous popularity back in the 1980's and '90's both for final pop and rock mastering, as well as by radio stations to draw and maintain listeners. Essentially they were very subtly designed harmonic generators that had a dynamically responding attribute.
I haven't yet heard an LDR attenuator myself, but wouldn't be surprised if their popularity could be linked to the same psycho-acoustic proclivity for those who enjoy their sound. All the reported benefits line-up with the same subjective responses of the listeners back when A.E.'s were being used regularly.
Perceived increases in "impact", "clarity", "bass response", and "loudness" were fairly common, until the process began to be overused in the initial battles of the "Loudness Wars", which eventually led to their falling out of favor. Utilized with subtlety, however, most listeners would never have perceived the devices' effects consciously, and would simply have preferred the sonic results.
I look forward to obtaining and experimenting with one of these LDR devices when time and budget permits. Maybe even as a gain control element in the negative feedback loop of an op-amp, if it can be used in a stable way.
@mbrennwa - Thanks for the re-link to those measurements, I have read all the way through the thread, and it was your measurements, and the anecdotal evidence supplied by others that have lead me to my conclusion.
@ All others - This thread and its presented debates certainly bring into relief the classic dichotomy in audio, the challenge of realistic "clinical" reproduction given the technologies of our time, vs. the need for a "euphonic" listener experience, whether or not that experience is an exact duplicate of the original production (it cannot be currently, although we continue to get closer asymptotically).
@ All others - This thread and its presented debates certainly bring into relief the classic dichotomy in audio, the challenge of realistic "clinical" reproduction given the technologies of our time, vs. the need for a "euphonic" listener experience, whether or not that experience is an exact duplicate of the original production (it cannot be currently, although we continue to get closer asymptotically).
Hello,
The title of this thread says it all, listening impressions.
I would suggest that you get some and not speculate. You might find it helpful.
There are essentially two issues with LDR volume controls. One is the nonlinearity of the LDR itself. Unless this is accounted for then the LDR is essentially useless.
The other is the small amount of harmonic distortion, well shown in mbrennwa's post. Yes, it's there. It's more than you get with a stepped attenuator. It's less than you get with any preamp. If one is bothered by this small amount of harmonic distortion, then simply avoid LDR volume controls.
If one reads the personal observations of listeners the favorable ones are generally from those who preferred the LDR unit to their preamp. It's a bit mixed with regards stepped attenuator comparisons.
If you start viewing the anode and cathode of the internal led, not as a connection satisfied by just a 7805 and a capacitor - which it appears most measurements are derived, the resulting audio of an LDR improves immensely. A simple LM317 arranged instead as a current regulator Vref/ R should start to give clues as to what is possible.
Next you need to remove all components in parallel with the anode and cathode
such as capacitors or potentiometers.
Having more than one input is easy, achieved by using more series pairs. The attribute
of Resistance off for a NSL32SR3 being 25m ohms can be used to great advantage as a contact less switch (when anode is off, and as a attenuator when current is reapplied) ,
Also to make your LDR attenuator have silence at zero volume
is also pretty easy to achieve.
I'd be curious to understand that as well.
Using a LM317 (or 100ma TL317 for that matter) as a current regulator works great with current set via the formula 2.5/R. If you make the R adjustable now you have an adjustable current regulator so you could control the LDR by adjusting R. But as far as the LDR is concerned it will simply be seeing a voltage at the + side of the LED (or voltage differential across the LED) where that voltage just happens to be coming from an adjustable current regulator. Since the control voltage is indeed coming from a regulator it's bound to be reasonably clean especially if the voltage driving the input of the current regulator is itself coming from a regulated source.
If the point of all this is that the LDR is now being controlled via a lower noise souce of power then I agree that's beneficial for sound quality.
I don't think noise is the issue; if it was then he would want to add capacitors across the LED but he says it is best with them removed.
That raises a curious thought: it is conceivable that Chris's method of feeding the LED increases noise, thus raising LF noise intermodulation (the slow LDR response would eliminate HF noise intermodulation) which could just about be audible and then misperceived as an improvement. The sound could be 'richer'. However, most likely that it makes no difference at all so the 'improvement' is all in the mind of the listener.
That raises a curious thought: it is conceivable that Chris's method of feeding the LED increases noise, thus raising LF noise intermodulation (the slow LDR response would eliminate HF noise intermodulation) which could just about be audible and then misperceived as an improvement. The sound could be 'richer'. However, most likely that it makes no difference at all so the 'improvement' is all in the mind of the listener.
Conceivable perhaps but unlikely that using a current regulator as LDR driver would increase noise (compared to what though?). I do use TL317s as a fixed current source in a buffer application and find them to be very stable and quiet. My own work with LDRs has convinced me that a low noise LDR control signal is better than a noisy one....up to a point since LDRs do self-filter higher frequency noise. We currently use simple 12/16 bit ladder DACs to drive our LDRs. Those control signals are low noise, stable and repeatable assuming the reference is also.
'Immensely' !.....Oh really ?.
'Extraordinary' !.....Oh my, the exaggerations keep getting bigger.
One thing that needs examination/research is the optical output 1/f noise of LED's when driven from voltage or current sources.
Dan.
If LEDs are good for biasing tubes etc., why would they be too noisy in an LDR?
I am suggesting that there may be a difference in the very low frequency (<10Hz) noise performance.
In an amplifier this is usually not of great consequence, but in a gain control element it may be ?.
Chris does not give description of the 'improvements'....this would be useful to help track down what is going on.
Dan.
In an amplifier this is usually not of great consequence, but in a gain control element it may be ?.
Chris does not give description of the 'improvements'....this would be useful to help track down what is going on.
Dan.
There's some good info in this stackexchange.com thread on driving LEDs that suggests there are inherent advantages to a current regulated LED over the traditional voltage control with a resistor. Still, it's not clear to me how this would translate into improved sound quality when used with an LDR unless the voltage control approach proved to somehow be unstable or produce unstable light output. Either ought to be measureable. I use voltage control on our LDRs with stable/repeatable results.
driver - How can I efficiently drive an LED? - Electrical Engineering Stack Exchange
driver - How can I efficiently drive an LED? - Electrical Engineering Stack Exchange
If there is an LF noise difference then it ought to be possible to measure this. Use an LED-LDR optocoupler, put some current through the LDR and see how the LDR noise voltage changes when the LED drive is changed from voltage to current. Even if a change is seen, I still doubt Chris's "immensely" claim; perhaps 'small' would be more accurate?