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Old 21st April 2012, 03:52 PM   #4521
soongsc is offline soongsc  Taiwan
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My matched LDRs came with measurements. Why not get yours and find out?
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Old 21st April 2012, 06:23 PM   #4522
tinitus is online now tinitus  Europe
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Originally Posted by soongsc View Post
Why not get yours and find out?
or maybe just build one, which shouldnt be too hard

ehh, wait a minute, that sounds strange, Im confused now
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Old 21st April 2012, 08:47 PM   #4523
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Originally Posted by soongsc View Post
My matched LDRs came with measurements. Why not get yours and find out?
Because I do not have this product and therefore I do not have this products measurements for left Right Channel balance. ...Yet more excuses and no measurements.

Cheers / Chris
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Old 22nd April 2012, 10:32 AM   #4524
soongsc is offline soongsc  Taiwan
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Originally Posted by tinitus View Post
or maybe just build one, which shouldnt be too hard

ehh, wait a minute, that sounds strange, Im confused now
Like this?

Click the image to open in full size.
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Last edited by soongsc; 22nd April 2012 at 10:35 AM.
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Old 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
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File Type: jpg Another clone crap.jpg (53.2 KB, 249 views)
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Old 22nd April 2012, 01:21 PM   #4526
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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
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Old 22nd April 2012, 01:56 PM   #4527
AndrewT is offline AndrewT  Scotland
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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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Old 22nd April 2012, 02:31 PM   #4528
godfrey is offline godfrey  South Africa
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Originally Posted by Chris Daly View Post
Accurate channel balance with LDR's is the the figure to strive toward, its the difference between a average LDR product and an exceptional one capable of accurate reproduction.
Yes, I agree.

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.
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Old 22nd April 2012, 03:00 PM   #4529
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Originally Posted by AndrewT View Post
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.
Hi Andrew
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
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Old 22nd April 2012, 03:03 PM   #4530
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Originally Posted by godfrey View Post
Yes, I agree.

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.
Hi Godfrey
Well explained Thank you
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