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Old 16th December 2010, 02:45 PM   #3851
udailey is offline udailey  United States
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I should also mention that of great importance and to be remembered is what George said about a very hot tip. A relatively cool tip will take a long time to solder/unsolder. Again use flux but also use a very hot tip and things will happen very quickly which is what we want. Count on your heatsink and blowing on the LDR to remove the heat before it gets destructive. Cool tips will be damaging. Your 10w/20w iron is not hot enough. A 30W+ iron will do the trick. I keep mine around 350-400C.

Anyone that has tried to contact me in the last few days please excuse my lack of attention. I will get to everyone today and have been busy with holiday preparations.
Uriah
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Old 16th December 2010, 04:15 PM   #3852
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I Visualize what you are going to do.. Pray.. Now apply flux to the joint Uriah
Uriah....at last something funny !
Never mind this being the removal procedure this is what I did building the bl....y thing !!
Talk about pray, visualize and ...talk to myself during the whole nerve racking process and then blow like a loony on the LDR's !!

Apologies for this technical contribution

Andrew
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Old 19th December 2010, 10:03 PM   #3853
markusA is offline markusA  Sweden
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I just want to add a thought on balanced operation and the Lightspeed.
Due to my current (other) project I've been forced to really take a look on balanced topology.
Although I'm a n0ob it seams to me there are two viable options for balanced operation.
1) Trasformercoupling and SE Lightspeed
2) Fully balanced build with servo

Just my $0.02, I don't know if it's worth anything?
Either way you still have to match the LDR to get L/R linearity.
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Old 20th December 2010, 01:34 AM   #3854
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Quote:
Originally Posted by markusA View Post
I just want to add a thought on balanced operation and the Lightspeed.
Due to my current (other) project I've been forced to really take a look on balanced topology.
Although I'm a n0ob it seams to me there are two viable options for balanced operation.
1) Trasformercoupling and SE Lightspeed
2) Fully balanced build with servo

Just my $0.02, I don't know if it's worth anything?
Either way you still have to match the LDR to get L/R linearity.
As for transformer coupling, it is a step backwards from the purity of the Lightspeed, they ring and have limited bandwidth as well as other problems with inductance resistance and other drawbacks.

For servoing "sensing" the output level and auto correction for any level L/R change, this works but has a detrimental effect on the sound as well being attached to the output, a bit like dc auto servos some say and myself you can heard them when compared to a manual nulled out offset voltage in a direct coupled active stage.

The best is still to pain stakingly match the LDR's at 5 different levels over the volume span anything else is a compromise on sound quality.

Cheers George
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Old 20th December 2010, 05:56 AM   #3855
markusA is offline markusA  Sweden
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I suppose you're right, it would be important to get a good trafo and it would still be affecting the sound. (The best one could hope for is negligible influence.)

As for the servo, I never said it was for L/R action. I was actually thinking it would be hard to implement that way. So, strictly servoing the actual balanced signal, not L/R.
(I suppose it could be done but it would be ugly and not optimal.)

Going for matched LDR's only will probably be the most transparent but matching will be important and you risk not having perfect balanced performance. In the end it's all about the price you're willing to pay.

It opens up for some interesting experiments though.
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Old 20th December 2010, 06:32 AM   #3856
ondesx is offline ondesx  France
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The best is still to pain stakingly match the LDR's at 5 different levels over the volume span anything else is a compromise on sound quality.
Even matched for 5 points isn't enough to insure a correct attenuation range ! Unfortunately...

It must be determined, for each attenuation step, the required current for ALL the LDRs... This is mandatory otherwise a mismatch will happen. Obviously, for balanced operation (and I know what I'm speaking...), these correct values are definitely required.

Last edited by ondesx; 20th December 2010 at 06:35 AM.
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Old 20th December 2010, 06:49 AM   #3857
soongsc is offline soongsc  Taiwan
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Adaptive linearization and matching.
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Old 20th December 2010, 06:52 AM   #3858
markusA is offline markusA  Sweden
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Let's not be hasty and dismiss georgehifi that fast.
There are problems but they might be of a theoretical nature. Mathematically correct might not be necessary for good irl operation.

Bearing in mind general speaker behaviour, small deviations might be negligible as long as the sonic signature is pleasing. Theory and reality doesn't always add up.
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Old 20th December 2010, 07:56 AM   #3859
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Any form of monitoring the resistance of the LDR's means it's going to be tacked on the signal path "not good" and this would be the only other way one could keep all LDR's tracking together, been there and done it. The only and best way is by matching them at the minimum of 5 points, this gives an overhaul deveation of around +- 1db, undetectable when using the NSL23SR2S which go down to 40ohms at 20mA low enough at a whisper for any system, save a pair of 110db horns or JBL's and such with high gain amps.
Cheers George
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Old 20th December 2010, 08:14 AM   #3860
soongsc is offline soongsc  Taiwan
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Quote:
Originally Posted by markusA View Post
Let's not be hasty and dismiss georgehifi that fast.
There are problems but they might be of a theoretical nature. Mathematically correct might not be necessary for good irl operation.

Bearing in mind general speaker behaviour, small deviations might be negligible as long as the sonic signature is pleasing. Theory and reality doesn't always add up.
I think with any good idea, other ideas are going to branch from it. Whether they be better is unknown. Is a VCCS controlled one better? Is the buffered one better? There are so many things involved in the sound quality that it's really hard to be sure which is the most dominant. Just for example, the Lightspeeds; if the original concept was just to remove the wipers from the signal path, it's hard to believe that research has proven this to have very good results if it had not been tried in practice.
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Last edited by soongsc; 20th December 2010 at 08:17 AM.
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