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Old 4th June 2009, 07:39 PM   #101
udailey is offline udailey  United States
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Well you still have time to go balanced of course. Make sure your CDP has balanced out.

So I spoke with Fred from Silonex. He says "whats the lowest ohms you get" and I say I have only tested with 80k in series with 5V so still its about 900-1.2k but that I dont care to much if I get 40ohms or not. He asks what the max resistance I get is and I say that I only test to 80k in series so my answer is the same. He says if I turn it off (the LED) then what? I say that a few megohms. He says 'see its in spec'. What? To me thats not in spec. They have a curve on their datasheet that shows an expected response and he says that that would be a typical response but not a guaranteed response and I said that I have over 500 and not one of them follows that graph so how can this be typical? We go back and forth a lot. It comes down to him not wanting an unhappy customer and Allied freaking out a bit because they are concerned that the 3k or so they have of these could all be junkers. So he wants to work with me to find a good solution that may even produce better matching results. Fine, this is fine, lets work on it and see what we come up with.
This means that your matches may take longer. Nearly a guarantee. I will email you all that have placed orders and explain what is going on. It may take longer or it may not. Allied already sent my other bag supposedly so I will try those out to.
He is going to send me some samples of other LDRs. I am hoping to use the same resistive material or at least get the same quality of beautiful sound out of any new ones. I will not compromise the sound quality even if distortion figures are better that does not guarantee a better quality of sound in my opinion. These are extremely low anyway since we are using them at one of the lowest distortion voltages we can. If you need to know more about this its in the datasheet and on the website. Check it out.
I will keep you updated. He is supposed to email me today to start the ball rolling on my needs.
Uriah
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Old 4th June 2009, 08:42 PM   #102
pchw is offline pchw  United States
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5V in series 80K is very close to full attenuation of a 100K pot. In fact, that is the exact case with my POS surplus 100K pot, it max out at 80K, way sooner than the specs. I don't recall seeing anything this low. Did you check how much current the LED draw?

I will check the lowest readings of those that I have measured so far when I get home. I will post the date code and reading for your reference.
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Old 4th June 2009, 09:11 PM   #103
udailey is offline udailey  United States
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Actually I have done some further testing. (Fred I forgot to recheck your numbers and will do so).
SO I tested at 18k and at 200k. Very promising. We may have to use 250k or higher like even 500k dual audio pots to control them, but this MAY be the BEST batch ever. When I got 1k at 80k I was crestfallen. Very upset that they were so terrible. However they were all within 300 ohms of each other. If I was going for 1k pots it would be heaven. So I went and tested at 200k. Almost all of them were at 3-3.4k. Very good news so far. Fred from Silonex had said they get really unpredictable at super low amps. I am at microamps and they seem promising. At 18k they were all around 260-300R. So maybe they proceed linearly. I need to check this with some massive trimmers. Then I need to make a prototype with a 250k - 500k somewhere around there dual log pot and see if we have a winner. If so I will be buying more and revising my recommendation for a circuit. That would only be that we should use a higher value than 100k. SO this is simply due to the inconsistencies in their manufacturing process, but hopefully it will work to our advantage today.
I will keep you all updated, you know that
Uriah
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Old 5th June 2009, 08:24 AM   #104
pchw is offline pchw  United States
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Quote:
Originally posted by pchw
5V in series 80K is very close to full attenuation of a 100K pot. In fact, that is the exact case with my POS surplus 100K pot, it max out at 80K, way sooner than the specs. I don't recall seeing anything this low. Did you check how much current the LED draw?

I will check the lowest readings of those that I have measured so far when I get home. I will post the date code and reading for your reference.
The 2 lowest readings from my batch have date 408. One was measured at 1.8K and the other measured at 2.5K with 5V in series of 80K. With 180K in series, both rised to above 10K. So, a 250K pot will work with these nicely.
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Old 5th June 2009, 01:48 PM   #105
udailey is offline udailey  United States
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Yesterday I ordered 50 25turn trimmers at 500k and 50 more at 1MOhm. This is very strange as normally I would be only testing up to 40k. However I LIKE this change of events for matching. So far anyway. We will see how testing turns out. This is costing a lot of money but hopefully it will be worth it and if it is hopefully Silonex got their act together and started getting these manufactured with higher quality control. Maybe its just a weird quirk.
Bought a few 250 and 500k dual log pots so I can build up prototype LSAs and test out the new LDRs after I find a few matches. THEN I will test out of this batch for you guys as long as things are looking good. Otherwise I will continue with the return and exchange with Allied.
Will keep you in the loop.
Uriah
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Old 5th June 2009, 03:24 PM   #106
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Uriah - would you recommend that I change my pots - currently using a 50k Alps and 1K trimmers?

Alan
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Old 5th June 2009, 04:05 PM   #107
udailey is offline udailey  United States
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Alan,
You have LDRs from an earlier matching that I think you are referring to. I think its best to use 100k with them. This new batch is acting completely different than any other batch I have ever matched. It might allow 500k pots. I have to get testing once I get my trimpots in. They are on order with Mouser.
So for you Alan, I would use a 100k pot as you will get greater range with the matched sets you have now.
For your recent order I dont know yet. I suspect 250k or 500k, not sure yet.
Uriah
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Old 7th June 2009, 11:41 AM   #108
ccliu is offline ccliu  Taiwan
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Is this still available?

I have sent email for 1 balanced stereo matched set.
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Old 7th June 2009, 12:54 PM   #109
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Uriah - I have sent more money for a second set of the newly matched LDRs.

I will wait until you know the best value for the pots before buying any.

Regards

Alan
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Old 8th June 2009, 03:33 PM   #110
udailey is offline udailey  United States
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Default First Round Results

I have tested 549 LDRs at 200k in series with 5.039VDC
Results are great and average resistance is 4296R at 200k in series with voltage. Min was 2.5k max was 6k.
This particular batch of LDRs is frankly weird. Maybe it will become the norm. Maybe they changed the manufacturing process. I dont know but their datasheet has not changed and these do not fit the datasheet. Nevertheless, they will work for our purposes.
Given this strange situation I didnt know what 4 points I would match at since normally my max resistance in series with 5VDC would be 40k and would result in numbers similar to those achieved with 200k. You can see where these LDRs present a bit of an unknown and are acting 'weird'. I want to provide you guys with LDRs that I know will function similar to the average Lightspeed in terms of overall output impedance. I will consider what to do next. I am considering testing half of them for use with a 250k pot and the other half for use with a 500k pot. The half that are measuring 5k-6k would be used with a 250k pot and the half that are measuring lower would be used with a 500k pot. I think its best if I measure that lower half next at about 400k and see how that works out. If they are getting to erattic because of the miniscule power they are getting then I will abort that plan and go for a 250k pot for all of them which would mean my next measuring would be at 150k, 75k, 37k or thereabouts. We will see what works best.
Uriah
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