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Old 6th August 2008, 08:37 PM   #1
Tolu is offline Tolu  Germany
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Default Attenuator: Sonic influence of voltage divider branches

Hi,

one question that concerns me:

How is the sonic influence of each part of a voltage divider? Or, is there a difference between them. Is it audible if I use better/ worse parts (relays/resistors) in the series or shunt part? Which one is the more important branch?
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Old 6th August 2008, 08:43 PM   #2
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Well, it seems like both are equally important, with shunt section maybe even more:

Shunt Attenuator Myth
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Old 6th August 2008, 09:25 PM   #3
KSTR is offline KSTR  Germany
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A voltage divider's gain is
g=R2/(R1+R2)=1/(1+R1/R2), with R2 being the lower resistor and R1 the upper.

We can apply an error/nonlinearity factor to each, like
R1*e1 and R2*e2,

then we can rewrite the gain as
g=1/(1+e*R1/R2), with e being e1/e2

As long as e1 and e2 are close to 1 (say, +-10% max), it doesn't matter much which one changes.

But the ratio of the resistors matters, the lower the gain (that is, the bigger the term R1/R2) the more the error dominates the gain equation denominator.

Net result is, as long is the error is low (which we shall assume) it doesn't matter which leg of the divider contributes to it. More important, the effect of any error is worst when the gain is very small and it goes to zero when the gain becomes 1. This is assuming zero drive impedance and infinite load impedance, otherwise these impedance must be factored in (drive in series with R1 and load parallel to R2). In a real world situation one will certainly have to experiment which variant of leg arrangement sounds and/or measures better, and often secondary/overlooked other effect (layout etc) may dominate the performance anyway.

And like (I think) was stated in that other thread, it may be wise to optimize for the mostly used level settings, which is only an option for the DIYer, of course.

- Klaus
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