Sorry,
but I don't understand why the Lightspeed attenuator should sound better than an Alps RK27112 or an reed-relay-based attenuator with Vishay Dale Resistors.
A LDR is no magic machine. It produces distortion and noise as well as a pot. It seems to be more difficult to get the same resistance values for the whole bandwith of regulation (synchronisation of both channels) than with a relay-based attenuator with 0,1% Rs.
Regards
Thomas
but I don't understand why the Lightspeed attenuator should sound better than an Alps RK27112 or an reed-relay-based attenuator with Vishay Dale Resistors.
A LDR is no magic machine. It produces distortion and noise as well as a pot. It seems to be more difficult to get the same resistance values for the whole bandwith of regulation (synchronisation of both channels) than with a relay-based attenuator with 0,1% Rs.
Regards
Thomas
Tolu said:
Can't speak of others but i've had pretty unpleasant experience with relays. Nice mechanical switches often sound good; relays do not. Maybe i've just been unlucky but a single relay contact junction is immediately audible in my system (Nais DS2Y).
Apparently mercury relays are less audible but at a price.
Tolu said:
You may be wrong here. It seems to produce a whole lot more distortion than a pot but it probably lacks the unpleasant distortion characteristic of relays.
As with other exotic audio solutions the final preference is based on listening. Maybe the LDR sounds so good because of its high distortion.
I think that relays are as variable as pots (and anything else). Undoubtedly, some sound bad and some don't.
My own experience is that an LDR volume control sounds better than an ALPs blue pot, but on a par with the relay switched attenuator I am comparing it with. I should stress that the relays and resistors used totally govern the sound in this case.
There are hundreds of types of relay that could be used, along with dozens of resistor types. That makes a lot of combinations.
And that's not even getting into the impedance matching (ie what impedance the source and sink see)
If someone tries to tell you that LDRs sound better than anything else, don't believe them unless they can convince you that they have tried every possible alternative. (This applies to anything of course).
I don't believe that a "contact" on it's own sounds bad (like in a pot or a relay). It depends on so many things. After all, the lightspeed itself has contacts... for the input and output phono plugs..perhaps the ultimate is to solder (or wirewrap??) all connections between the source and speakers
My own experience is that an LDR volume control sounds better than an ALPs blue pot, but on a par with the relay switched attenuator I am comparing it with. I should stress that the relays and resistors used totally govern the sound in this case.
There are hundreds of types of relay that could be used, along with dozens of resistor types. That makes a lot of combinations.
And that's not even getting into the impedance matching (ie what impedance the source and sink see)
If someone tries to tell you that LDRs sound better than anything else, don't believe them unless they can convince you that they have tried every possible alternative. (This applies to anything of course).
I don't believe that a "contact" on it's own sounds bad (like in a pot or a relay). It depends on so many things. After all, the lightspeed itself has contacts... for the input and output phono plugs..perhaps the ultimate is to solder (or wirewrap??) all connections between the source and speakers
Tolu said:
it looks like you have not read this long thread from the beginning...
a possible explanation have been proposed, though indeed no such thing as a convincing "scientific proof" have been shown (but are there any in "hi-end" audio? ).Nevertheless, a lot of independent people who have tried have confirmed the listening impressions. Thus, even in case the proposed explanation is not the right one, I guess that some reasons there should be... if you have doubts, try for yourself and let us know about your own impressions. And, if you can, try to find / prove the reasons behind it. That would be helpful.
OK, this may indeed be one possibility (though NOT the most likely, IMHO). However, this begins to remind me of silly tube vs. solid state wars... please, not once again!
@Unixman:
Yes, you caught me right-handed. I have read only the first 5 and the last 5 pages!
@beau2317:
Which combination (type, manufacturer) of relays and resistors have you compared on par with LDRs (model?).
I am of sceptical mind, so I am wondering why the whole industry (except of a dozen paradise birds) doesn't use this phenomenal attenuator for their products, especially regardind the low costs. Don't understand me wrong, but I am looking for the rub in it!
If I can get the Silonex parts anywhere in Germany and have a little time left, I will try to build one for comparison purpose.
My new preamp with the Opamp LME49710 from National should beat a rocket when you just look at the datasheet but in reality there is a big lack of warmth and bass.
So, believe it whether you can't explain it.
Regards
Thomas
Yes, you caught me right-handed. I have read only the first 5 and the last 5 pages!
@beau2317:
Which combination (type, manufacturer) of relays and resistors have you compared on par with LDRs (model?).
I am of sceptical mind, so I am wondering why the whole industry (except of a dozen paradise birds) doesn't use this phenomenal attenuator for their products, especially regardind the low costs. Don't understand me wrong, but I am looking for the rub in it!
If I can get the Silonex parts anywhere in Germany and have a little time left, I will try to build one for comparison purpose.
My new preamp with the Opamp LME49710 from National should beat a rocket when you just look at the datasheet but in reality there is a big lack of warmth and bass.
So, believe it whether you can't explain it.
Regards
Thomas
Tolu said:@Unixman:
Yes, you caught me right-handed. I have read only the first 5 and the last 5 pages!
I am of sceptical mind, so I am wondering why the whole industry (except of a dozen paradise birds) doesn't use this phenomenal attenuator for their products, especially regardind the low costs. Don't understand me wrong, but I am looking for the rub in it!
If I can get the Silonex parts anywhere in Germany and have a little time left, I will try to build one for comparison purpose.Thomas
Thomas, you need to have a little patience, read more of the thread, also be a little less sceptical, make one yourself, and here is a little help to start you off with seeing your short on time, supply in Germany of the NSL-32SR2S, and if you don't have the time to build one, it's your loss.
http://www.rsonline.de/cgi-bin/bv/r...cdladdlgekejlfcefeceeldgondhgi.0&cacheID=deie
Cheers George
I am not sure of the relay manufacturer, but as far as I know somebody selected them for good audio performance. The resistors currently are some japanese metal film, quite good quality but not real top of line stuff. I am thinking of trying some different resistors. I am not finished with this yet..or with the LDRs. Lots of things to try.
Good relays I've used in the past were sealed reed relays designed for precision work, not the lower cost more traditional type relays that are often exposed to the air. I think these relays are also that sort of thing. I've heard that mercury wetted can also be good but I've not (consciously) tried these.
Hi,
getting next week 4 matched NSL-32SR3 from another member! Try to build one with Georges blueprint.
My questions:
1. Has anybody built the lightspeed with a current regulating DAC or resistance ladder and µController so far? How does it work and sound?
2. Has anybody built an input selection with optocouplers? How does it sound?
3. How about the developing of resistance in the life cycle of an Silonex optocoupler? Are they constant or is there a shifting in time response? E. g. will 0.5 mA result in 2000 Ohms now and 2 years later!
Thanks in advance.
Regards
Thomas
P.S.: Don't use Safari for Windows! It's a bug machine!
getting next week 4 matched NSL-32SR3 from another member! Try to build one with Georges blueprint.
My questions:
1. Has anybody built the lightspeed with a current regulating DAC or resistance ladder and µController so far? How does it work and sound?
2. Has anybody built an input selection with optocouplers? How does it sound?
3. How about the developing of resistance in the life cycle of an Silonex optocoupler? Are they constant or is there a shifting in time response? E. g. will 0.5 mA result in 2000 Ohms now and 2 years later!
Thanks in advance.
Regards
Thomas
P.S.: Don't use Safari for Windows! It's a bug machine!
Hi Thomas,glad to see your building one, you may run into trouble with channel balance with the NSL32SR3 as even thou they are matched, their resistance span (60R- 25meg) is much wider than the NSL32SR2 (40R-5meg)
I doubt whether the matching will be good enough so you don't hear channel imbalance between left and right, if so you can use the 1k calibration pot as a form of balance so you will with patience get a good centre image. Then you can decide whether it's worth trying to get some NSL32SR2S (sorted) for yourself.
And to your question about long term tracking stability, no probelm my original latest MkII prototype has been on permenently now for over I think 5 years 24/7 and it is behaving just like the first day I built it.
Cheers George
I doubt whether the matching will be good enough so you don't hear channel imbalance between left and right, if so you can use the 1k calibration pot as a form of balance so you will with patience get a good centre image. Then you can decide whether it's worth trying to get some NSL32SR2S (sorted) for yourself.
And to your question about long term tracking stability, no probelm my original latest MkII prototype has been on permenently now for over I think 5 years 24/7 and it is behaving just like the first day I built it.
Cheers George
R3 Types
I have one unit with R3 and another with R2. If using a stereo control for both channels, the R3 will work best with about a 25K log pot. Should end up somewhere close to 10K impedance.
Mine are high range, J grade sorted, and that is about what they ended up.
The grade also makes a fair difference. I play with the range of pots to get close to the same impdeance in both channels. Control tracking with mono controls.
George
I have one unit with R3 and another with R2. If using a stereo control for both channels, the R3 will work best with about a 25K log pot. Should end up somewhere close to 10K impedance.
Mine are high range, J grade sorted, and that is about what they ended up.
The grade also makes a fair difference. I play with the range of pots to get close to the same impdeance in both channels. Control tracking with mono controls.
George
Hi George and Panelhead,
I will first start with SR3 because it's easier to get them. Next try will be SR2S.
My questions 1 and 2 are pending. I am very interested how fine you can regulate the LDR. What are the smallest steps you can get by the smallest voltage/current change?
If you are simulating a 20k log pot with constant input impedance in series/shunt-configuration you need a series resistance at a level of -32dB with value of 19500 Ohms but at -64dB with R1 of 19988 Ohms. So, for an attenuation of 32 steps of -1 dB you need a series resistance change of about 15 Ohms. Is it possible to get this result via voltage/current change (perhaps by DAC)?
One question confuses me: The pot: log or lin. Some say log, some say lin. George wrote about 100k lin, in the drawing it's 100k log. Panelhead says 25k log for SR3.
Regards
Thomas
I will first start with SR3 because it's easier to get them. Next try will be SR2S.
My questions 1 and 2 are pending. I am very interested how fine you can regulate the LDR. What are the smallest steps you can get by the smallest voltage/current change?
If you are simulating a 20k log pot with constant input impedance in series/shunt-configuration you need a series resistance at a level of -32dB with value of 19500 Ohms but at -64dB with R1 of 19988 Ohms. So, for an attenuation of 32 steps of -1 dB you need a series resistance change of about 15 Ohms. Is it possible to get this result via voltage/current change (perhaps by DAC)?
One question confuses me: The pot: log or lin. Some say log, some say lin. George wrote about 100k lin, in the drawing it's 100k log. Panelhead says 25k log for SR3.
Regards
Thomas
Tolu said:
Listen to Georgehifi, he either knows more about these or he is sharing more than anyone else.
The impedance of the control pot is more complicated than it looks. There are many grades, A,B,C, D etc. The lower the letter grade the lower the impedance of the resistive element at a fixed current. So A, B, C, D grade LDR's might work with a much higher impedance pot compared to J, K,L grade.
My SR3 are J or K grade, the SR2 are D,E grade. This where I will lose you, but using a control per pair of LDR's, the SR2 are controled with a 230K pot. The SR3 controled with a 47K. These are the actual measured pot values.
Both Measure 10 - 12k impedance from input to ground as the pot is rotated full range.
My resistance values are doubled because there is a pot for each channel. Most have both channels being controlled by a single pot. That is why I stated that a 25K log pot should work with the SR3 type you have.
As far as the dac controlls and self calibrators, this looks good. But how complicated is it going to be in practice? Once you have matched the LDR's and found the value pot that give the desired impedance you are done with the Lightspeed method.
Now if I would stop diddling with the power suply, all there would be left to do is listen to music.
George
Sorry for my inscrutable enunciation!
I want to remote control the lightspeed without a pot and will simplify and improve the matching process. My goal is a channel deviation of about 0.5 to 1 dB.
Therefore I am considering to solve it with a 12 or 16Bit-DAC in a range of 0-2.5V. And that was my question. How big is the smallest resistance step with the least voltage change? I need an accuracy of about 15 Ohm per step.
Has anybody a plot or graph of the dependency of voltage (or current) and resistance? That would be very helpful in advance.
Regards
Thomas
I want to remote control the lightspeed without a pot and will simplify and improve the matching process. My goal is a channel deviation of about 0.5 to 1 dB.
Therefore I am considering to solve it with a 12 or 16Bit-DAC in a range of 0-2.5V. And that was my question. How big is the smallest resistance step with the least voltage change? I need an accuracy of about 15 Ohm per step.
Has anybody a plot or graph of the dependency of voltage (or current) and resistance? That would be very helpful in advance.
Regards
Thomas
Tolu said:Sorry for my inscrutable enunciation!
I want to remote control the lightspeed without a pot and will simplify and improve the matching process. My goal is a channel deviation of about 0.5 to 1 dB.
Therefore I am considering to solve it with a 12 or 16Bit-DAC in a range of 0-2.5V. And that was my question. How big is the smallest resistance step with the least voltage change? I need an accuracy of about 15 Ohm per step.
Has anybody a plot or graph of the dependency of voltage (or current) and resistance? That would be very helpful in advance.
Regards
Thomas
Hi Thomas,
the matched quad I got from Panelhead has a 1dB max deviation, so using a calibration you can reach better results even with unmatched optocouplers.
To drive the leds you need at least a series resistor. The LDR resistance is plotted versus the led current (in the datasheet), so you have to control this parameter.
Using a DAC you need either a series resistor or a VCCS (voltage controlled current source)
Regards
Andrea