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Old 22nd March 2013, 02:48 PM   #1
JanErik is offline JanErik  Finland
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Default Variable gain op-amp for volume control (vs normal voltage divider pot)

What are the advantages and drawbacks of either approach? I see there will be no pots in the actual signal route. But could it be more sensitive to noise anyhow? And an open track in the pot could of course make the circuit go infinite gain.
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Old 22nd March 2013, 02:59 PM   #2
djoffe is online now djoffe  United States
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The feedback volume controls offer the best combination of SNR versus gain...that is...they only give the gain they need, so the SNR is always optimum.

Doug Self has examples in his most recent preamp design. Doug attributes the topology to work done by Peter Baxandall.

In this approach, if the wiper goes open, the gain doesn't go to infinite, but it does go to the maximum gain that the stage was capable of, for example, 16 dB.


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