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Inverting or non-inverting for audio applications?
ricko_uk:
Hi,
when it comes to audio applications, assuming signal polarity is not relevant for the specific case (i.e. mono signal just for signal quality analisys), what is best configuration to use?
Inverting or non inverting? and Why?
The only thing I am interested is the highest quality signal amplification, nothing else.
Thank you :)
SiliconWizard:
Are you specifically talking about opamp-based amplification?
ricko_uk:
Thank you SiliconWizard,
Yes... But... What would be the alternatives you seem to imply? If you are referring to various classes (B, D etc) of audio amplifiers the yes because I want to use a op-amp specifically as power dissipation is not an issue. I want to stick to linear solution (and no switching anywhere on the entire board, not even for the PSU.
Thank you :)
schmitt trigger:
Some time ago, there was a heated argument over the DIYAudio forum.
Someone cited a paper, as far as I remember one of the “Analogue Dialogue” series by ADI.
There was a case presented in which the non-inverting configuration was preferred.
TimFox:
In general, the inverting configuration, with a resistor in series between the input and summing point, has inferior noise performance due to the voltage noise of a relatively large resistor, but does not suffer from common-mode-induced distortion.
The non-inverting configuration is therefore usually preferred for noise-sensitive applications, since the resistors in the feedback network can be made smaller than what one would use in the inverting configuration. The common-mode problem can be important, since the common-mode voltage equals the input signal voltage. If there be a non-linear input current due to the common-mode voltage (common with BJTs), it flows through the source impedance (including any input coupling capacitor). The voltage from that current looks exactly like an input voltage, and will not be affected by feedback.
An interesting variation, almost never used, is to place the input signal between the feedback voltage divider and the inverting input, with the non-inverting input grounded, thus avoiding both problems but requiring a non-grounded source (possibly a phono pickup, microphone, or transformer secondary).
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