I have purchased, but yet to build, Uriah's Lighter Note kit. I plan to use it with a DCB1 buffer in hot rod mode (which generates a lot of heat) in the same case. I never gave the heat issue much thought until now, but I see that I need to.
The LDR board is separate from the power supply and small. Would it be good enough to place the LDR board in a small box to keep temps consistent? If so, should it be plastic, metal, or wood? Do I need to fill it with wax, silicone, or epoxy?
If I understand correctly, it is not the actual temperature that is the issue, it is keeping the temperature consistent between the LDRs. A slow gradual rise in case temperature is OK as long as both LDR rise at the same rate.
The LDR board is separate from the power supply and small. Would it be good enough to place the LDR board in a small box to keep temps consistent? If so, should it be plastic, metal, or wood? Do I need to fill it with wax, silicone, or epoxy?
If I understand correctly, it is not the actual temperature that is the issue, it is keeping the temperature consistent between the LDRs. A slow gradual rise in case temperature is OK as long as both LDR rise at the same rate.
I had built one used four trimmer for each LDR's. each LDR can independent
adjusted the resistance at four position of the pot. 7, 9, 12 and 5 O'clock.
For series LDR I adjusted at 7.5 O'clock= 20kr, 9=19kr, 12=15kr, 5= 50r, at
7 O'clock position the series LDR will open the resistor is greater than 20mr
the output is dead silent.
For shunt LDR at 7 O'clock=40r,9=1kr,12=5kr,5=20kr.
This attenuator had built in the channel balance pot and high/low impedance select switch also. The one I used now I adjusted high to 20kr and low for 10kr.
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Yes they are just that sensitive, especially when they are at higher resistances. At 250R or so you cant budge them but at 10k a 1 degree difference can mean hundreds of ohms. The motion of air from a door opening in another room can make a difference.
I have tested with two LDRs being monitored by one DMM each and have found that some LDRs will move more than others even though they get the same power and are initially set to the same resistance. So this is why I wait about an hour before I start testing and every time I change to a higher resistance I wait about 15 minutes before beginning the next test. I have a LDR attenuator running now that has been running for 2 years with the top off. My channel balance is pretty nice but its in a huge room and there are no hotspots around it. I have never built a LDR attenuator INTO an amp chassis. Not saying I wouldnt but I havent so I cant speak from experience. I can only say that table top testing of individual LDRs makes me think that, yes, temp changes will get them moving and the fact that they might move at different rates could show as a channel imbalance.
I recently was sent a DIY implementation of a Lightspeed for a look. The gentleman had issues with series LDRs not changing value and the balance being off to boot. Here he had done a point to point on breadboard using largish gauge wires as signal and power wires. The problem he had was that it took so much heat to get the wires to accept solder that the LDRs were damaged and in fact one gang of the control pot was damaged so that it no longer worked, while the other gang was okay. Heat kills.
I build LDR attenuators from time to time and sometimes I will find that the LDRs match according to my datasheets but past the max value of my datasheets they do NOT match. I never assume that they will but we can always hope.
With this build I have been able to solve the problem. Usually its one LDR of the 4 that is misbehaving at higher values. So lets say that at max resistance its sitting at 14k and its mate is around 12k and lets say this permeates a bit lower so that at 2k they are a great match and up to 6k they are a decent match and beyond they seem to be hundreds of ohms away from each other. I can fix this with a high value resistor in parallel with the misbehaving LDR. Oh LORD! You cant be serious! A real resistor in the signal?! Well, yes its a very high value that usually fixes the problem and its in parallel with a relatively low value LDR so the amount of signal passing the resistor is quite small in comparison to the offending LDR and to my ears and my Audio Precision the sound is not compromised subjectively or objectively. I start with a 249k and work my way to two 249k in parallel then try a 100k or a 75k. This is usually all it takes.. one of these options will make the problem disappear.
This brings us to gootee's suggestion about parallel LDRs. I made a batch of 10 of these boards a few years ago. I still have one of them. I goofed them because I designed it using the default pin sizes in my pcb layout software and never expanded them. SO I had to drill out several of them and then never rebuilt them. One reason only. It was just beginning to be to much for the builders. I was considering 8 LDRs where 4 are dynamic and 4 stay the same value during operation for fine tuning balance and for limiting max resistance. It works and its nice.
Back to matching: I match up to an average of 6k for a few reasons. 1: 6k sounds fantastic to me compared to other values so thats a subjective reason. 2: LDRs are relatively stable at 6k. They start to get a little squirrely around 5k but 6k is not to bad. Squirrely meaning affected to a greater degree by heat. So if I match to an average of 6k I can be sure I am selling the customer a reality up to that point. When I say an average of 6k I mean that I choose a voltage and current that results in most of the LDRs on the test boards to be grouping around 6k. Still I will have many up into 12-15k but most at 6k.
In no way should anyone assume that a set of LDRs that are tested to, lets say 8k, should be a great match at 15k. They might be but I dont know if they are.
So some things can be done here. If its a Lightspeed implementation a trimmer of a few hundred K can be placed in rheostat mode across each of the gangs of the 100k control pot. Max resistance of the LDRs can be brought a bit lower. Lower means more stable. So you can now control your Lightspeed's total resistance.
Lost in all these posts is a way to increase your Lightspeeds total resistance. A 100R multiturn trimmer in series with the 5V fed TO the volume pot. Around 10R will make dramatic changes in max resistance and you will need the multiturn capability as its very dramatic changes with just a touch of the dial on the trimmer.
I have tested with two LDRs being monitored by one DMM each and have found that some LDRs will move more than others even though they get the same power and are initially set to the same resistance. So this is why I wait about an hour before I start testing and every time I change to a higher resistance I wait about 15 minutes before beginning the next test. I have a LDR attenuator running now that has been running for 2 years with the top off. My channel balance is pretty nice but its in a huge room and there are no hotspots around it. I have never built a LDR attenuator INTO an amp chassis. Not saying I wouldnt but I havent so I cant speak from experience. I can only say that table top testing of individual LDRs makes me think that, yes, temp changes will get them moving and the fact that they might move at different rates could show as a channel imbalance.
I recently was sent a DIY implementation of a Lightspeed for a look. The gentleman had issues with series LDRs not changing value and the balance being off to boot. Here he had done a point to point on breadboard using largish gauge wires as signal and power wires. The problem he had was that it took so much heat to get the wires to accept solder that the LDRs were damaged and in fact one gang of the control pot was damaged so that it no longer worked, while the other gang was okay. Heat kills.
I build LDR attenuators from time to time and sometimes I will find that the LDRs match according to my datasheets but past the max value of my datasheets they do NOT match. I never assume that they will but we can always hope.
With this build I have been able to solve the problem. Usually its one LDR of the 4 that is misbehaving at higher values. So lets say that at max resistance its sitting at 14k and its mate is around 12k and lets say this permeates a bit lower so that at 2k they are a great match and up to 6k they are a decent match and beyond they seem to be hundreds of ohms away from each other. I can fix this with a high value resistor in parallel with the misbehaving LDR. Oh LORD! You cant be serious! A real resistor in the signal?! Well, yes its a very high value that usually fixes the problem and its in parallel with a relatively low value LDR so the amount of signal passing the resistor is quite small in comparison to the offending LDR and to my ears and my Audio Precision the sound is not compromised subjectively or objectively. I start with a 249k and work my way to two 249k in parallel then try a 100k or a 75k. This is usually all it takes.. one of these options will make the problem disappear.
This brings us to gootee's suggestion about parallel LDRs. I made a batch of 10 of these boards a few years ago. I still have one of them. I goofed them because I designed it using the default pin sizes in my pcb layout software and never expanded them. SO I had to drill out several of them and then never rebuilt them. One reason only. It was just beginning to be to much for the builders. I was considering 8 LDRs where 4 are dynamic and 4 stay the same value during operation for fine tuning balance and for limiting max resistance. It works and its nice.
Back to matching: I match up to an average of 6k for a few reasons. 1: 6k sounds fantastic to me compared to other values so thats a subjective reason. 2: LDRs are relatively stable at 6k. They start to get a little squirrely around 5k but 6k is not to bad. Squirrely meaning affected to a greater degree by heat. So if I match to an average of 6k I can be sure I am selling the customer a reality up to that point. When I say an average of 6k I mean that I choose a voltage and current that results in most of the LDRs on the test boards to be grouping around 6k. Still I will have many up into 12-15k but most at 6k.
In no way should anyone assume that a set of LDRs that are tested to, lets say 8k, should be a great match at 15k. They might be but I dont know if they are.
So some things can be done here. If its a Lightspeed implementation a trimmer of a few hundred K can be placed in rheostat mode across each of the gangs of the 100k control pot. Max resistance of the LDRs can be brought a bit lower. Lower means more stable. So you can now control your Lightspeed's total resistance.
Lost in all these posts is a way to increase your Lightspeeds total resistance. A 100R multiturn trimmer in series with the 5V fed TO the volume pot. Around 10R will make dramatic changes in max resistance and you will need the multiturn capability as its very dramatic changes with just a touch of the dial on the trimmer.
I should add that in light of my tests and finding LDRs changing at different rates when subjected to exactly the same power, ambient conditions and having been proven to match at certain resistances I would assume that glueing them together will help but will not guarantee symmetry change. I would never discourage glueing and waxing or boxing. I like these approaches. I just have seen proof that this will not be a fix-all type solution.
I have been discouraged by the quality of these LDRs over the years. I truly love the sound there is no doubt. The manufacturer, Silonex, quite obviously changes the manufacturing plant almost yearly. I have noticed the LDR being built in Canada, Mexico, California and China. I buy in bags of 1k so I usually get original quality control stickers on my bags so I can glean some info that way. How can you make a process better when you consistently change the place of manufacture? The wires have gone from nice and thick, malleable wires to so small and fragile as to cause trouble in the matching jig because I was counting on a little spring action in the wire. Right now they wires have gone back to a respectable size. When I break them open I have noticed the internals have changed. There used to be a sort of lens between the resistive and LED side. I have seen a rubbery tube for the light to shine through and the one I just cracked open has what I suspect is hot glue on top of the LED. These are all different ways to diffuse the light. I can make no guesses as to the better way to do this. It does give differing heat absorbing mass to the LDR.
I just hooked up the cracked open LDR, minus LED, to the DMM and got 1700R. Blowing on it made zero difference. Can we assume its the temp of the LED? I know that we are looking at differences of micro-amps making changes to LDR resistance so I think we can assume that stable voltage and stable current are of importance. Differing currents over the LED cause the Vf of the LED to change which bolsters the argument for a solid supply.
Well, anyway.. That all said and still nothing sounds better than an LDR in replace of resistors and pots.
I have been discouraged by the quality of these LDRs over the years. I truly love the sound there is no doubt. The manufacturer, Silonex, quite obviously changes the manufacturing plant almost yearly. I have noticed the LDR being built in Canada, Mexico, California and China. I buy in bags of 1k so I usually get original quality control stickers on my bags so I can glean some info that way. How can you make a process better when you consistently change the place of manufacture? The wires have gone from nice and thick, malleable wires to so small and fragile as to cause trouble in the matching jig because I was counting on a little spring action in the wire. Right now they wires have gone back to a respectable size. When I break them open I have noticed the internals have changed. There used to be a sort of lens between the resistive and LED side. I have seen a rubbery tube for the light to shine through and the one I just cracked open has what I suspect is hot glue on top of the LED. These are all different ways to diffuse the light. I can make no guesses as to the better way to do this. It does give differing heat absorbing mass to the LDR.
I just hooked up the cracked open LDR, minus LED, to the DMM and got 1700R. Blowing on it made zero difference. Can we assume its the temp of the LED? I know that we are looking at differences of micro-amps making changes to LDR resistance so I think we can assume that stable voltage and stable current are of importance. Differing currents over the LED cause the Vf of the LED to change which bolsters the argument for a solid supply.
Well, anyway.. That all said and still nothing sounds better than an LDR in replace of resistors and pots.
Mine looks like this post
http://www.diyaudio.com/forums/anal...otrodded-blue-dcb1-build-255.html#post3319899
You can "almost" see the actual lightspeed on bottown right. Mounted it above 2 of the transistors.
My dcb1 does not get hot at all.
http://www.diyaudio.com/forums/anal...otrodded-blue-dcb1-build-255.html#post3319899
You can "almost" see the actual lightspeed on bottown right. Mounted it above 2 of the transistors.
My dcb1 does not get hot at all.
You can't get much closer to the heat source. Some of the higher current hot rod implementations require huge heat sinks, so I suspect if you started to crank up the current, stability could be a problem in that config.
On the other hand: if you are that close to the mosfets and there are no stability issues, maybe heat isn't an issue. The mosfets likely generate constant and even heat keeping the temps of the LDRs also constant. So maybe in the end, high heat may be OK as long as it is even and constant.
On the other hand: if you are that close to the mosfets and there are no stability issues, maybe heat isn't an issue. The mosfets likely generate constant and even heat keeping the temps of the LDRs also constant. So maybe in the end, high heat may be OK as long as it is even and constant.
Just like to point out to those who like the technical details :
The LDRs for sale through this thread aren't the exact ones used in the Lightspeed.
Thread: Silonex NSL-32SR2
Lightspeed: Silonex NSL-32SR2S
This wasn't clear to me until I investigated further and that's why I posted this link before:
Silonex - NSL-32SR2S - Optoelectronics & Lighting - Optocouplers/Optoisolators - Allied Electronics
Implication: if you want to hear a real Lightspeed like circuit, use the fancier parts.
The LDRs for sale through this thread aren't the exact ones used in the Lightspeed.
Thread: Silonex NSL-32SR2
Lightspeed: Silonex NSL-32SR2S
This wasn't clear to me until I investigated further and that's why I posted this link before:
Silonex - NSL-32SR2S - Optoelectronics & Lighting - Optocouplers/Optoisolators - Allied Electronics
Implication: if you want to hear a real Lightspeed like circuit, use the fancier parts.
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You are correct AudioLapDance.
Typical ON resistance @ 20mA for the NSL32RS2S is 40ohms
" " " " " " NSL32SR2 is not stated and can be anything
Also the 1mA resistance is a much tighter grading on the NSL32SR2S
The NSL32SR2S are batched and are graded ABCDEF&G and sent to suppliers/retailers as a graded batch packages.
This is why the NSL32SR2S is 50% more costly than the NSL32SR2
Cheers George
They are more than just basic sorted and matched, they have less variation in many of their other parameters as well. A good analogy would be two 170 FETs that are matched (but only at certain points) and a 389 whose two FET are very similar in many parameters.
Sorry, I didn't mean to step on any toes.
I'm sure good preamps could be made from both. It's just as DIYers we often, nay must!, go to extremes and choose parts matched at the edges of function and performance!
George,
I've followed your argument before and on reading it again, I think you are assuming too much from the datasheet.
As far as I can see the S graded components are selected components from the SAME production.
The extra cost is surely down to the extra work/processing of measuring and batching.
I cannot see how the datasheet is confirming that different production components are being used for the S graded components.
I've followed your argument before and on reading it again, I think you are assuming too much from the datasheet.
As far as I can see the S graded components are selected components from the SAME production.
The extra cost is surely down to the extra work/processing of measuring and batching.
I cannot see how the datasheet is confirming that different production components are being used for the S graded components.
What I said and also R on is typicaly lower resistance giving better low volume capabilities. And being batched if you match these they will give you many more matched sets with lower R on than the NSL32SR2 can, unless you hammer them with too much current and shorten their life.
Cheers George
Wow. Thanks for your latest excellent contributions to everyone's knowledge. You have made many, many important contributions, here, and it has not gone un-noticed.