If you use a 100k pot, ala Pauls boards, you will get about 1k or so of resistance. Probably not what you wanted. To get the output desired in a lightspeed you will need a 500k pot.
I have used the LM334 one time on one set of LDRs and found that it did not track the same as it had with a pot. I always wait at least 15min to test before measuring for matching. Using the LM334 I did not do so. I was only seeing what kind of range I could get. NOW, I think you could drive the LM334 with the 100k pot and drive the LDRs with that, but again I have to test more.
I think, and am not sure, but I think the LDRs need to be tested and matched in the same way they will be driven. All this is based on one mild one minute test and as the saying goes 'your guess is as good as mine'.
This sale of LDRs is for the lightspeed and while Pauls is a variation on an idea it is not a lightspeeed.
Uriah
I have used the LM334 one time on one set of LDRs and found that it did not track the same as it had with a pot. I always wait at least 15min to test before measuring for matching. Using the LM334 I did not do so. I was only seeing what kind of range I could get. NOW, I think you could drive the LM334 with the 100k pot and drive the LDRs with that, but again I have to test more.
I think, and am not sure, but I think the LDRs need to be tested and matched in the same way they will be driven. All this is based on one mild one minute test and as the saying goes 'your guess is as good as mine'.
This sale of LDRs is for the lightspeed and while Pauls is a variation on an idea it is not a lightspeeed.
Uriah
Love Michael Percy's shop. Dont like the wait though, but I guess I dont need to be in such a hurry to build amps.
I just got done printing off the little datasheets that go with each pair of LDRs so you guys will get two datasheets for each single ended set of 4 and either 4 datasheets or one big one for each set of 8 for balanced.
Here is an example:
LDRs numberes 233 and 234 happen to be right next to each other and are a good match. Nowhere near the best match but still a good match and will work great in the Lightspeed. I wanted to use a decent but not fantastic pair as an example so you can see how to decide whether to use a pair as the shunt pair or the series pair.
So here we have:
LDR number___100k_____200k_____300k_____400k
233___________1693_____4383_____8073_____12280
234___________1677_____4430_____8365_____12614
Except at 100k the resistance of 233 is a bit lower than 234. It will be the louder channel so you will trim this resistor. Probably there will be no need to trim, but if you wanted perfection...
This pair of LDRs exhibit their best tracking from 100k-200k. This is a good candidate for shunt LDRs. WHY? Because when they are in half volume or lower they dont track as well as they would at full to half volume on your 500k pot. If you can notice the difference you would notice it at lower volumes because of the way your ear works. At high volume you will probably be partying anyway. What would be a good candidate for series LDRs? The best candidate for series LDRs has best tracking in 300-400k readings or all the way across. Put your very best as series.
If I feel a set of LDRs would be best as series or shunt I will write that on the datasheet. If I do not write anything then that means they could be for either position. Nevertheless, the matching went really really well and I dont see anyone hearing a difference on any of them anyway. Its nice to be able to match a huge number of LDRs for that reason.
Uriah
I just got done printing off the little datasheets that go with each pair of LDRs so you guys will get two datasheets for each single ended set of 4 and either 4 datasheets or one big one for each set of 8 for balanced.
Here is an example:
LDRs numberes 233 and 234 happen to be right next to each other and are a good match. Nowhere near the best match but still a good match and will work great in the Lightspeed. I wanted to use a decent but not fantastic pair as an example so you can see how to decide whether to use a pair as the shunt pair or the series pair.
So here we have:
LDR number___100k_____200k_____300k_____400k
233___________1693_____4383_____8073_____12280
234___________1677_____4430_____8365_____12614
Except at 100k the resistance of 233 is a bit lower than 234. It will be the louder channel so you will trim this resistor. Probably there will be no need to trim, but if you wanted perfection...
This pair of LDRs exhibit their best tracking from 100k-200k. This is a good candidate for shunt LDRs. WHY? Because when they are in half volume or lower they dont track as well as they would at full to half volume on your 500k pot. If you can notice the difference you would notice it at lower volumes because of the way your ear works. At high volume you will probably be partying anyway. What would be a good candidate for series LDRs? The best candidate for series LDRs has best tracking in 300-400k readings or all the way across. Put your very best as series.
If I feel a set of LDRs would be best as series or shunt I will write that on the datasheet. If I do not write anything then that means they could be for either position. Nevertheless, the matching went really really well and I dont see anyone hearing a difference on any of them anyway. Its nice to be able to match a huge number of LDRs for that reason.
Uriah
Salut Uriah
Hmm again - 1k might actually be perfect - it's the value of the IR resistor in my DIY DACs...
However, more flexibility in the future might be nice - I'll ask Paul in the other thread. I did BTW mention in this thread that I'll be using his circuit - but I know you've got a lot of takers.
@+
Vernon
Hmm again - 1k might actually be perfect - it's the value of the IR resistor in my DIY DACs...
However, more flexibility in the future might be nice - I'll ask Paul in the other thread. I did BTW mention in this thread that I'll be using his circuit - but I know you've got a lot of takers.
@+
Vernon
However the recommendation by George is to use an audio taper pot. You can use a linear taper of course but the rise in volume might be even more extreme. As it is the Lightspeed jumps very quickly in volume and takes a little getting used to.
I think Rod Elliot has a page on turning a linear pot into a log pot by adding a resistor to its wiper to ground or something similar.
The audio taper starts to rise in volume very slowly and then really takes off in the last 1/3 of the pot. Because it is following a curve set by our logarithmic hearing.
Uriah
I think Rod Elliot has a page on turning a linear pot into a log pot by adding a resistor to its wiper to ground or something similar.
The audio taper starts to rise in volume very slowly and then really takes off in the last 1/3 of the pot. Because it is following a curve set by our logarithmic hearing.
Uriah
Hi Uriah -
I'm sorry but I'm still quite new to DIY and I'm a little confused...
Based on the discussion in the latter pages of this thread, is it safe to directly substitute a 500k pot for the 100k pot in the schematic posted in the link in "Instructions..." (linked in your signature)???
While this may seem obvious... it's not to a noobie - or, at least, it's not to me... I try not to post questions with obvious answers and I also try to use the 'search' function on the various forums.
I really appreciate your efforts in offering these LDR.
Thanks,
I'm sorry but I'm still quite new to DIY and I'm a little confused...
Based on the discussion in the latter pages of this thread, is it safe to directly substitute a 500k pot for the 100k pot in the schematic posted in the link in "Instructions..." (linked in your signature)???
While this may seem obvious... it's not to a noobie - or, at least, it's not to me... I try not to post questions with obvious answers and I also try to use the 'search' function on the various forums.
I really appreciate your efforts in offering these LDR.
Thanks,
All USA shipments went out this morning.
I just finished printing the Customs forms. Way faster than handwriting!
So now to apply them to the boxes and get the international boxes to the post office.
Thanks everyone for trying my matched LDRs and for helping get out quantity up on the overall LDR buy from Allied if you purchased unmatched LDRs.
I am done matching LDRs for a while. I have about 4 sets left and will be keeping them.
IF YOU WANT MATCHED LDRS please contact me and I will put you on a waiting list. I imagine I will do more matching in about a month but right now I would like to work on an amplifier.
If you have questions about building the Lightspeed please go to the DIYaudioProjects.com website and view the build and project in the projects section. It is very detailed. Just change the 100k pot into a 500k pot and it will work. You can use P2P wiring or use a breadboard.
If you still have questions please email me but if it is obvious you have no clue as to how it works I will refer you to the project first.
I really appreciate you guys and take a lot of pride in the fact you are using my matched LDRs. It has been amazing to me to watch how many international builders there are vs US builders. About 25% are US and then it is NewZealand, Singapore, Australia, France, UK, Germany, Italy in about that order. I might have Singapore and NewZealand reversed or they might be same quantity but man there are a lot of orders out of the total from both countries.
I hope you all have fun and I know you will enjoy this project. If you insist on using a 100k pot please dont contact me as since June 4th I have been saying I think a 100k wont work. I have included a single gang pot in each order and it is of 500kOhm. You did not pay for this pot. If you do not like the pot please feel free to find one on your own that you like more. I know this pot is of low quality, but please consider that we are only using it as a variable resistor and not to pass an audio signal through. It does its job very well. It seems to me to be of same quality of the pot I use in mine that I got from Radio Shack. Works like a dream and I love the smooth rotation.
Please dont forget you will need a trimmer for whichever channel is louder. I can recommend pots over 5k and up to about 25k. Which one you choose is up to you. I like a large resistance multiturn pot. This gives me the most flexibility while allowing fine tuning that a single turn might not offer.
If anyone would like to start a Lightspeed build thread please consider going to the already existing Lightspeed thread started by GeorgeHIFI and posting there to get George's thread some more attention and more posts. He is attempting to get a Passive PreAmp forum going on DIYaudio and to get that going the moderators and admins have told him he needs more attention on his original thread. Please give him a hand, he deserves it.
When I am done shipping I will do a final count and donate $3 per order originating from DIYaudio to DIYaudio. I do have several orders originating from the DIYaudioProjects thread and since the admin of that thread has refused any donations I will be donating that money to the Ronald McDonald House a charity for children.
Thanks guys and gals
Uriah
I just finished printing the Customs forms. Way faster than handwriting!
So now to apply them to the boxes and get the international boxes to the post office.
Thanks everyone for trying my matched LDRs and for helping get out quantity up on the overall LDR buy from Allied if you purchased unmatched LDRs.
I am done matching LDRs for a while. I have about 4 sets left and will be keeping them.
IF YOU WANT MATCHED LDRS please contact me and I will put you on a waiting list. I imagine I will do more matching in about a month but right now I would like to work on an amplifier.
If you have questions about building the Lightspeed please go to the DIYaudioProjects.com website and view the build and project in the projects section. It is very detailed. Just change the 100k pot into a 500k pot and it will work. You can use P2P wiring or use a breadboard.
If you still have questions please email me but if it is obvious you have no clue as to how it works I will refer you to the project first.
I really appreciate you guys and take a lot of pride in the fact you are using my matched LDRs. It has been amazing to me to watch how many international builders there are vs US builders. About 25% are US and then it is NewZealand, Singapore, Australia, France, UK, Germany, Italy in about that order. I might have Singapore and NewZealand reversed or they might be same quantity but man there are a lot of orders out of the total from both countries.
I hope you all have fun and I know you will enjoy this project. If you insist on using a 100k pot please dont contact me as since June 4th I have been saying I think a 100k wont work. I have included a single gang pot in each order and it is of 500kOhm. You did not pay for this pot. If you do not like the pot please feel free to find one on your own that you like more. I know this pot is of low quality, but please consider that we are only using it as a variable resistor and not to pass an audio signal through. It does its job very well. It seems to me to be of same quality of the pot I use in mine that I got from Radio Shack. Works like a dream and I love the smooth rotation.
Please dont forget you will need a trimmer for whichever channel is louder. I can recommend pots over 5k and up to about 25k. Which one you choose is up to you. I like a large resistance multiturn pot. This gives me the most flexibility while allowing fine tuning that a single turn might not offer.
If anyone would like to start a Lightspeed build thread please consider going to the already existing Lightspeed thread started by GeorgeHIFI and posting there to get George's thread some more attention and more posts. He is attempting to get a Passive PreAmp forum going on DIYaudio and to get that going the moderators and admins have told him he needs more attention on his original thread. Please give him a hand, he deserves it.
When I am done shipping I will do a final count and donate $3 per order originating from DIYaudio to DIYaudio. I do have several orders originating from the DIYaudioProjects thread and since the admin of that thread has refused any donations I will be donating that money to the Ronald McDonald House a charity for children.
Thanks guys and gals
Uriah
Great news Uriah, could I suggest that you do the matching in Winter - although if your aircon breaks down then you will be freezing!
Whatever - I think you need a break from all this matching - how you can consider the possibility of a third marathon effort is beyond me.
Thanks as always for your efforts and enthusiasm.
Alan
Whatever - I think you need a break from all this matching - how you can consider the possibility of a third marathon effort is beyond me.
Thanks as always for your efforts and enthusiasm.
Alan
Well, Alan I have an idea for an integrated amp but it needs matching so thats the driver behind that idea about matching again. Selling more matched sets would pay for buying maybe a hundred boards and then I could offer those. I think the Lightspeed is magic with LM3886 and I have a few other ideas to integrate into the amp. I know everyone is mono amp crazy and it has its merits, but I like the idea of a single board with everything on it using a single heatsink in a small enclosure. Nice layout with proper grounding will get rid of some of the noise that is often present in stereo configurations. Well, anyway, I will give more info on that when I get the layout done and a prototype built. Will be my fun for the month.
Uriah
Uriah
Another 500K stereo pot
Though not as expensive as the TKD from PERCY, still not cheap but one of high quality. The PEC pots are very good. This looks like what I will use.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=KKA5041S28-ND
Concerning Mr. Percy, i have discovered the secret to getting great service from him: calculate to the best of your ability your order.
Make a PAYPAL transfer with the parts list attached and send him an email also detailing what you want.
This proves to him you are a serious customer and you will get your parts QUICKLY!!!! He is lucky enough to be very busy and I do not doubt he gets bogged down with orders that go nowhere. When "faced" with a REAL order, meaning money has been transferred, the man reacts quickly. He is my favorite parts supplier especially since I have learned to work with him.
Uriah, THANKS for your group buy!!!!
Though not as expensive as the TKD from PERCY, still not cheap but one of high quality. The PEC pots are very good. This looks like what I will use.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=KKA5041S28-ND
Concerning Mr. Percy, i have discovered the secret to getting great service from him: calculate to the best of your ability your order.
Make a PAYPAL transfer with the parts list attached and send him an email also detailing what you want.
This proves to him you are a serious customer and you will get your parts QUICKLY!!!! He is lucky enough to be very busy and I do not doubt he gets bogged down with orders that go nowhere. When "faced" with a REAL order, meaning money has been transferred, the man reacts quickly. He is my favorite parts supplier especially since I have learned to work with him.
Uriah, THANKS for your group buy!!!!
Hey Rick,
thanks for that Michael Percy tip. Thats the tactic I will use next time. I can understand his latency when I consider what you just said.
Please make sure your pots you buy are not guitar pots per say. They have a weird taper to them. You want an audio or log taper and you could probably get away with a linear taper if you had to.
The APEXJR pots may be regular audio pots but check with him. Otherwise they would be great pots and its nice to take care of Steve at ApexJr. He certainly takes care of us.
Uriah
thanks for that Michael Percy tip. Thats the tactic I will use next time. I can understand his latency when I consider what you just said.
Please make sure your pots you buy are not guitar pots per say. They have a weird taper to them. You want an audio or log taper and you could probably get away with a linear taper if you had to.
The APEXJR pots may be regular audio pots but check with him. Otherwise they would be great pots and its nice to take care of Steve at ApexJr. He certainly takes care of us.
Uriah
Could this be useful? UC39431?
If this has been brought up, please accept my apologies.
Seemed interesting.
http://focus.ti.com/lit/ds/slus192/slus192.pdf
Available from DIGIKEY for about ten dollars.
I am not up to the task; doesn't someone here have a learned opinion?
Thanks,
If this has been brought up, please accept my apologies.
Seemed interesting.
http://focus.ti.com/lit/ds/slus192/slus192.pdf
Available from DIGIKEY for about ten dollars.
I am not up to the task; doesn't someone here have a learned opinion?
Thanks,
Cool little IC. Available in PDIP so we could socket it. So you should try it and tell us what you think I am sure you could throw it together on veroboard/perfboard or just P2P but boards would be easier.
Also try the LM334 or LM385. LM334 is very good at controlling the LDRs and getting super high resistance out of them. I have the LM385 but only tried the circuit once and goofed it. Now I have time to try again.
Uriah
I am sure you could throw it together on veroboard/perfboard or just P2P but boards would be easier.Also try the LM334 or LM385. LM334 is very good at controlling the LDRs and getting super high resistance out of them. I have the LM385 but only tried the circuit once and goofed it. Now I have time to try again.
Uriah
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