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Analog Line Level Preamplifiers , Passive Preamps, Crossovers, etc. 

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21st April 2012, 03:52 PM  #4521 
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Join Date: Mar 2005
Location: Taiwan

My matched LDRs came with measurements. Why not get yours and find out?
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Hear the real thing! 
21st April 2012, 06:23 PM  #4522 
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21st April 2012, 08:47 PM  #4523 
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Join Date: Sep 2004
Location: hobart tasmania


22nd April 2012, 10:32 AM  #4524  
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Join Date: Mar 2005
Location: Taiwan

Quote:
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Hear the real thing! Last edited by soongsc; 22nd April 2012 at 10:35 AM. 

22nd April 2012, 11:40 AM  #4525 
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Or this one, another clone piece of crap, advertised as being new and superior, around the traps, one of my customers got it on loan from the maker and took this shot of the guts.
One can clearly see it's just bad a clone of a MkI Lightspeed Attenuator using series resistors and shunt really cheap LDR's. Cheers George 
22nd April 2012, 01:21 PM  #4526 
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Join Date: Sep 2004
Location: hobart tasmania

Silonex NSL32SR2 is the part I use in L pad format, the same part used in this threads product.
I look forward to measurements being published for Left Right channel balance through full attenuation range Cheers / Chris 
22nd April 2012, 01:56 PM  #4527 
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Join Date: Jul 2004
Location: Scottish Borders

Chris,
you are chasing a parameter that is relatively unimportant. A 100k vol pot that is followed by a 100k input impedance resistor does not hold a constant load impedance for the Source feeding that vol pot. That tolerable Zin as seen by the Source does not create added distortion, if the Source is adequately specified to drive the cables and load that follow. Adding together the resistances of LDRseries & LDRshunt gives the equivalent to the vol pot resistance. It does not matter that the total resistance seen by the Source is not absolutely constant nor does it matter if one channel is slightly different from the other. Try measuring actual dual track log pots. I have found they vary quite a bit in total resistance. What matters for "stereo balance" is the resistance ratio of the Series : Shunt elements. Go and do your homework and when you understand or get stuck come back and clarify where you then stand.
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regards Andrew T. 
22nd April 2012, 02:31 PM  #4528  
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Join Date: Nov 2009
Location: Cape Town

Quote:
However, calculating the aggregate resistance for each channel and comparing those numbers tells you nothing about the channel balance. You need to calculate the attenuation of each channel and compare those figures. Example: L Series = 21700 Ohms L Shunt = 1550 Ohms aggregate = 23250 Ohms Attenuation = 23.5dB R Series = 22800 Ohms R Shunt = 450 Ohms aggregate = 23250 Ohms Attenuation = 34.3dB The aggregate resistances are exactly the same but the channel balance is out by more than 10dB. The left channel will subjectively be twice as loud as the right channel. 

22nd April 2012, 03:00 PM  #4529  
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Join Date: Sep 2004
Location: hobart tasmania

Quote:
Whilst this circuit uses a dual pot, mine uses a single, which is an advantage in avoiding imprecise tracking. It would be interesting to see what this product does series shunt L vs series shunt R . given that its purpose is a stereo audio device, We could also start to see the effect of a fixed voltage and variable potentiometer relative to the photocell series/ shunt resistance variance. Measurement, ..the more we know, the less we guess. Cheers / Chris 

22nd April 2012, 03:03 PM  #4530  
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Join Date: Sep 2004
Location: hobart tasmania

Quote:
Well explained Thank you 

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