I for matching
Just wondering about the different matching currents used.
E.g. NP showed in #1328 his matching of NSL32RS2S with 0,01mA (-> ca 15k) to 2mA (->ca 80R).
George, you prefer 2,5mA to 20mA.
May we assume, that matched pairs at 2,5mA to 20mA are still matching well enough with lower currents, down to 0,01mA? And vv.?
Cheers, Frank
Just wondering about the different matching currents used.
E.g. NP showed in #1328 his matching of NSL32RS2S with 0,01mA (-> ca 15k) to 2mA (->ca 80R).
George, you prefer 2,5mA to 20mA.
May we assume, that matched pairs at 2,5mA to 20mA are still matching well enough with lower currents, down to 0,01mA? And vv.?
Cheers, Frank
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Guys,
Just get several resistors and a 5V supply. Start measureing and recording. Its not anything to get worried about exactly what current to use or what voltage to use. Just as long as you are giving each one the same power for the same amount of time and recording it. Oh, same temperature to.
George tests at 5 different settings. Does it matter what 5 settings? Not really as long as they are the same for all the LDRs you test in that batch.
Test them all at once. Testing a few today and a few tomorrow wont work. They wont match even if the numbers say that they do.
I now test at 5 points as well. 4 was fine. 3 is NOT fine. My new setup lets me do it faster so I can take the time to do 5 settings..
Dont go to 20mA. Maybe 10mA at very most. Nearly zero difference between 10mA and 20. But huge between .1 and .05 because they are saturating at 10mA.
Uriah
Just get several resistors and a 5V supply. Start measureing and recording. Its not anything to get worried about exactly what current to use or what voltage to use. Just as long as you are giving each one the same power for the same amount of time and recording it. Oh, same temperature to.
George tests at 5 different settings. Does it matter what 5 settings? Not really as long as they are the same for all the LDRs you test in that batch.
Test them all at once. Testing a few today and a few tomorrow wont work. They wont match even if the numbers say that they do.
I now test at 5 points as well. 4 was fine. 3 is NOT fine. My new setup lets me do it faster so I can take the time to do 5 settings..
Dont go to 20mA. Maybe 10mA at very most. Nearly zero difference between 10mA and 20. But huge between .1 and .05 because they are saturating at 10mA.
Uriah
Banned
Joined 2002
Banned
Joined 2002
Thanks udailey,
I think my results confirm your findings. High current values are fairly stable but at low currents do take time to settle and actually continue to change over time.
I am trying to find a consistent test procedure. I did these tests (see attachment) shortly after sun rise, so it is interesting to see the change in ambient temperature. I have converted the actual resistances to a value between 0 and 1023. This makes it easier to see the trends and to sort the LDRs mathematically (I hope).
Initially the low current readings drop quickly but stabilize after 10 or so readings then gradually drop over time. I stopped and started the tests a few times to see what happens.
EDIT: I'll need to repeat this test once the ambient temperature stops rising.
regards
I think my results confirm your findings. High current values are fairly stable but at low currents do take time to settle and actually continue to change over time.
I am trying to find a consistent test procedure. I did these tests (see attachment) shortly after sun rise, so it is interesting to see the change in ambient temperature. I have converted the actual resistances to a value between 0 and 1023. This makes it easier to see the trends and to sort the LDRs mathematically (I hope).
Initially the low current readings drop quickly but stabilize after 10 or so readings then gradually drop over time. I stopped and started the tests a few times to see what happens.
EDIT: I'll need to repeat this test once the ambient temperature stops rising.
regards
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Greg what you have to remember is that, if you build it as I do it is in a fairly constant environment, the second regulated power supply inside the production Lightspeed Attenuator keeps the temp fairly constant inside the sealed chassis.
Also, and this is very important all the 4 x NSL32sr2S LDR's are set in very close proximity to each other and "potted" together in hard wax, is the way it should be built, and then you will have no drift problem over time. My prototype has now been on 24/7 for more than 5 years and is still in perfect channel balance as are the hundreds I have sent to customers, not one has come back with balance problems
It is important to match from 2.5 to 20 mA, as each pair are at either (opposite) high or low " max 20mA or min " depending if you are high or low position on the volume control
Cheers George
Also, and this is very important all the 4 x NSL32sr2S LDR's are set in very close proximity to each other and "potted" together in hard wax, is the way it should be built, and then you will have no drift problem over time. My prototype has now been on 24/7 for more than 5 years and is still in perfect channel balance as are the hundreds I have sent to customers, not one has come back with balance problems
It is important to match from 2.5 to 20 mA, as each pair are at either (opposite) high or low " max 20mA or min " depending if you are high or low position on the volume control
Cheers George
Hi George,
Thanks again. As you know, the temperature is only an issue during the matching proccess. If you are matching 50 or 100 LDRs and it takes a few hours, the temperature could have changed many degrees especially if you started at 6:00 am. Once you have your matched LDRs then drift doesn't matter that much if they all drift the same. Doing what you do in the production version really eliminates the issue altogether and ensures a constant impedance.
Hi George,
I have almost completed my light speed boards. All the components are hard wired from point to point using ultra pure silver wires. The power supply stage is pretty stable at 5.03 V. The cabinet is made of teak wood. Will post the pics once the light speed is completely ready...
1. What is the expected burn-in hours for light speed ?
Best regards,
Bins.
I have almost completed my light speed boards. All the components are hard wired from point to point using ultra pure silver wires. The power supply stage is pretty stable at 5.03 V. The cabinet is made of teak wood. Will post the pics once the light speed is completely ready...
1. What is the expected burn-in hours for light speed ?
Best regards,
Bins.
It takes about 15mins to warm up on first power up, leave your volume control at half possition no music during playing during this initial warm up, just to add to the anticipated excitment.
Then treat your self for an eargasm.
Leave switched on 24/7 after that, when not in use leave powered up at half level.
Cheers George
Hi George,
Great....
1. What is the required input and output impedance values for the optimal performance ? Is there any way to adjust that ?
Best regards,
Bins.
Great....
1. What is the required input and output impedance values for the optimal performance ? Is there any way to adjust that ?
Best regards,
Bins.
If all 4 are quad matched then it behaves much like an approx 8k log passive pot.
As for load and source impedances.
Source, cdp/phono stage or da convertors output impedance should be less than <200ohm, this not a fast rule as I've had customers with 1kohm sources that have had great results.
Poweramp input should be more than >50kohm, again not a fast rule as we have done multi golden ear tests where no-one could pick the difference till we droped the variable input impedance of the poweramp in the test down to 33kohm
Cheers George
As for load and source impedances.
Source, cdp/phono stage or da convertors output impedance should be less than <200ohm, this not a fast rule as I've had customers with 1kohm sources that have had great results.
Poweramp input should be more than >50kohm, again not a fast rule as we have done multi golden ear tests where no-one could pick the difference till we droped the variable input impedance of the poweramp in the test down to 33kohm
Cheers George
Ready for final assembly...
Hello George,
Finally, I have completed the power supply and light speed boards. There is no PCB involved in my version. All the point to point wiring is done using ultra pure silver wires having Teflon insulation. Also, got the wood cabinet completely polished. The light speed will be finally assembled this week end.
Will post you the pictures on Sunday.
Best regards,
Bins.
Hello George,
Finally, I have completed the power supply and light speed boards. There is no PCB involved in my version. All the point to point wiring is done using ultra pure silver wires having Teflon insulation. Also, got the wood cabinet completely polished. The light speed will be finally assembled this week end.
Will post you the pictures on Sunday.
Best regards,
Bins.
A bit more info on the Dartzeel.
Are we learning? no switching in the signal path, and a Lightspeed for a volume control, pitty the reviewer thought it was a tad colored sounding, probably put that down to the no feedback active gain stage.
Absolute Sounds review
The DarTZeel NHB-18NS Preamplifier | AVguide
and we have the Stereophile review
http://www.stereophile.com/solidpreamps/607dart/
Cheers George
Are we learning? no switching in the signal path, and a Lightspeed for a volume control, pitty the reviewer thought it was a tad colored sounding, probably put that down to the no feedback active gain stage.
Absolute Sounds review
The DarTZeel NHB-18NS Preamplifier | AVguide
and we have the Stereophile review
http://www.stereophile.com/solidpreamps/607dart/
Cheers George
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I decided to integrate a lightspeed and the interconnects right into the CD player thus eliminating yet another RCA set from the signal path. A rather significant improvement.
Series LDR's tracked well from 50ohm to 55K corresponding to pot travel 0 - 130K.
Shunt LDR's 70ohm to 44K corresponding to 200ohm - 115K.
Using a 250K pot I paralleled a 300K resistor across the portion controlling the series and 220K on the shunt side giving me fairly smooth travel from feint to driver blowing. A rather simple yet effective tweak.
Series LDR's tracked well from 50ohm to 55K corresponding to pot travel 0 - 130K.
Shunt LDR's 70ohm to 44K corresponding to 200ohm - 115K.
Using a 250K pot I paralleled a 300K resistor across the portion controlling the series and 220K on the shunt side giving me fairly smooth travel from feint to driver blowing. A rather simple yet effective tweak.
I don't think that the impedance question is that important!
The maximum output imp. is reached at -6 dB. If you have 10k input imp. you have a range between -oo and -19 dB where the output imp. is lower than 1k! With 5k inp.imp. you can go until -11 dB and you'll have a max of 1.25k.
Many tube amp circuits work with 100k or 250k pots.
The maximum output imp. is reached at -6 dB. If you have 10k input imp. you have a range between -oo and -19 dB where the output imp. is lower than 1k! With 5k inp.imp. you can go until -11 dB and you'll have a max of 1.25k.
Many tube amp circuits work with 100k or 250k pots.
Good work Bins, it's been a long time comming.
Good to see that you like so much, as many others have, and the satisfaction of building one yourself. This is why I gave the circuit on how to diy, it maybe detracts from my production Lightspeed Attenuator sales a little, but I think that people that have electronic knowledge to build one would not purchase a production one anyway.
What it does it get the word out about potentiometers and their pathetic wiper contacts and active preamps, that they are not needed for the ultimate in controling the volume from the source.
Cheers George
Good to see that you like so much, as many others have, and the satisfaction of building one yourself. This is why I gave the circuit on how to diy, it maybe detracts from my production Lightspeed Attenuator sales a little, but I think that people that have electronic knowledge to build one would not purchase a production one anyway.
What it does it get the word out about potentiometers and their pathetic wiper contacts and active preamps, that they are not needed for the ultimate in controling the volume from the source.
Cheers George
Thanks...
Hello George,
I became really thrilled after hearing the light speed output. I never thought that I was missing so much of details with my old pre-amp. Thanks a lot for your support.
Can we use the light speed with a phono stage / cassette deck ?
Best regards,
Bins.
Hello George,
I became really thrilled after hearing the light speed output. I never thought that I was missing so much of details with my old pre-amp. Thanks a lot for your support.
Can we use the light speed with a phono stage / cassette deck ?
Best regards,
Bins.
No problem, so long as their output impedance's are below 100ohms and have enough output voltage.
Cheers George