R
RogerFoote
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:shock: Cool!
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StephenGiles
Well-known member
A good trick here would be to have the panner under voltage control - not easy I should think. How would you go about this Wayne, optos or PWM of 4016s?
I too would like to learn more about " non-linear distortion caused by potentiometer wiper-current. ". :?:
JR
JR
I "suppose" it's marketing BS, but am always interested when I hear about a common design practice causing distortion. If true, what a huge opportunity to improve so much circuitry in wide use everywhere. 
The only non-linearties I am aware of wrt wiper/resistive element contact, are similar to switch/jack contacts so limited to contamination or oxidation.
I got to learn more than I wanted about wiper design with one oddball pot series where there were less fingers on the wiper (per track) than optimal and wiper bounce during rotation could cause momentary open circuits. Wipers bounce occurs more often than you would expect due to small surface irregularities, but most wipers have several fingers in parallel so there is always one or two making contact at any time. These momentary opens are what you hear when a pot gets dirty or worn and sounds scratchy when rotated.
JR
PS: Indeed one could come up with appropriate pan laws, and there might be some merit in a current source summing topology if enough channels are involved, as we've discussed before. I would caution against substituing VCAa for potentiometers in an attempt to reduce "distortion" since the distortion mechanisms that I am aware of are all greater in VCAs.
The only non-linearties I am aware of wrt wiper/resistive element contact, are similar to switch/jack contacts so limited to contamination or oxidation. I got to learn more than I wanted about wiper design with one oddball pot series where there were less fingers on the wiper (per track) than optimal and wiper bounce during rotation could cause momentary open circuits. Wipers bounce occurs more often than you would expect due to small surface irregularities, but most wipers have several fingers in parallel so there is always one or two making contact at any time. These momentary opens are what you hear when a pot gets dirty or worn and sounds scratchy when rotated.
JR
PS: Indeed one could come up with appropriate pan laws, and there might be some merit in a current source summing topology if enough channels are involved, as we've discussed before. I would caution against substituing VCAa for potentiometers in an attempt to reduce "distortion" since the distortion mechanisms that I am aware of are all greater in VCAs.
StephenGiles
Well-known member
[quote author="mediatechnology"]Thanks Stephen for your reply.
On this one you could make the pot a VCA. But the span would be 0 to -6 dB for Left to Center, and -6 dB to full attenuation for Center to Right. So not tidy at all to deal with but possible.
I've also looked at modifying this one for combined voltage control. As shown it is a panner only:
http://www.thatcorp.com/datashts/dn120.pdf
What I wanted to do in the above was combine the fade, pan and mute functions so that both VCAs do double/triple duty instead of just voltage-controlled panning. Another proposed "trick" to that one is to eliminate the I-V converter and sum the VCA output currents directly into the mix bus.[/quote]
Mmmmm Barberpole Phasing driver possibilities perhaps??
On this one you could make the pot a VCA. But the span would be 0 to -6 dB for Left to Center, and -6 dB to full attenuation for Center to Right. So not tidy at all to deal with but possible.
I've also looked at modifying this one for combined voltage control. As shown it is a panner only:
http://www.thatcorp.com/datashts/dn120.pdf
What I wanted to do in the above was combine the fade, pan and mute functions so that both VCAs do double/triple duty instead of just voltage-controlled panning. Another proposed "trick" to that one is to eliminate the I-V converter and sum the VCA output currents directly into the mix bus.[/quote]
Mmmmm Barberpole Phasing driver possibilities perhaps??
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