I don't really know in what forum to ask...
Can I put a simple shunt volume control in front of differential line receiver ? Just as attached, but without the two opamps buffering the inputs of the receiver. Any problems I might run into ?
It's to sum the outputs of a pcm1794 (after I/V conversion).
Can I put a simple shunt volume control in front of differential line receiver ? Just as attached, but without the two opamps buffering the inputs of the receiver. Any problems I might run into ?
It's to sum the outputs of a pcm1794 (after I/V conversion).
Attachments
You would have to use low value resistors and a pot infront of the existing diff stage (inc resistors). This may mean that when the volume is attenuated a lot you place too much load on the driving stage.
Think of it as the same impednace problem with any passive pre-amp.
Think of it as the same impednace problem with any passive pre-amp.
What I had in mind:
4.7K resistors for the fixed resistors of the shunt and also 4.7K for the input resistor of the receiver. 22k resistors for the feedback around the opamp. A 10k stepped attenuator as shunt.
I can tailor the values of the attenuator to get true logarithmic attenuation. I'm not overly concerned by the current drawn by the shunt as the I/V stage is buffered by class A buffers iddling at 20ma. The whole thing is of course in the same box, no cables involved here.
4.7K resistors for the fixed resistors of the shunt and also 4.7K for the input resistor of the receiver. 22k resistors for the feedback around the opamp. A 10k stepped attenuator as shunt.
I can tailor the values of the attenuator to get true logarithmic attenuation. I'm not overly concerned by the current drawn by the shunt as the I/V stage is buffered by class A buffers iddling at 20ma. The whole thing is of course in the same box, no cables involved here.
Doesn't sound too bad. There may be some funny curve characteristic due to interaction between the shunt and input resistors, but other than that OK I think.
Is there a reason you can't just use one side of the converter with a conventional unbalanced level control? As you seem to be ending up with an unbalanced output anyway.
Is there a reason you can't just use one side of the converter with a conventional unbalanced level control? As you seem to be ending up with an unbalanced output anyway.
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