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Old 3rd February 2011, 12:41 AM   #11
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Originally Posted by Francec View Post
Thanks Don, if by DSP you mean control of the digital signal to achieve a loudness method of control then we aren't talking about the same thing.

Frank
Ah, I thought that "you" were discussing DSP processing to achieve "loudness control". I see you are actually discussing using something (for example, DSP) to make a "loudness control" circuit, implemented in a PGA2310 or similar, to track a "volume control" implemented in a a PGA2310 or similar. In this case, the thread I referred to is still relevant, as it discusses how to make a "loudness control" track a "volume control". My original suggestion was all-analog, but it required a scarce part (a 6-gang pot). I'm currently looking for suitable "electronic potentiometer" chips so that I can drive 6 such channels/chips from one physical pot.
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Old 3rd February 2011, 12:57 AM   #12
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The AD5206 is a 6-channel 8-bit (256 step) digital pot available in 10k, 50k & 100k. I just built an 8-channel PIC-controlled pot using 2*AD5204s.

w
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Old 3rd February 2011, 01:09 AM   #13
Francec is offline Francec  Australia
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Don, do you mean like this?

Silicon Chip Online - 6-Channel IR Remote Volume Control - Part 1

Frank
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Old 3rd February 2011, 10:46 AM   #14
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w,
Do you know of such a chip that accepts a voltage or an up/down pulse train as a control input? I'd like to avoid a PIC or glue logic if possible.

Frank,
I'll go get my paper copy of the magazine and see.

Thank you both.
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Old 3rd February 2011, 05:21 PM   #15
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Here's a dual-pot 8-bit volatile chip from Maxim, MAX5389:- http://datasheets.maxim-ic.com/en/ds/MAX5389.pdf. It has a simple up/down interface. You can get ones that remember their last setting. It's a matter of searching through by category on a suppliers website such as Farnell, RS or Digikey. This is a linear pot, but it can be made into a pseudo-logarithmic one by adding a resistor from the wiper to GND, see:- ESP - A Better Volume Control.

You have to read the datasheets to find out what the distortion, linearity and accuracy are. This make finding the best chip fairly labour-intensive.

w
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Old 3rd February 2011, 11:28 PM   #16
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Originally Posted by wakibaki View Post
Here's a dual-pot 8-bit volatile chip from Maxim, MAX5389:- http://datasheets.maxim-ic.com/en/ds/MAX5389.pdf. ...
You have to read the datasheets to find out what the distortion, linearity and accuracy are. This make finding the best chip fairly labour-intensive.

w
Thanks. That chip appears suitable for rotary encoder control. I want to use a "real" pot for control, but it's not hard to build a pulse generator to interface the pot to the chip(s).

For my initial proof of concept, I'm less concerned about chip performance and more about cost and availability at this end of the world. I believe it will work, and the circuit sim appears to confirm this, but there is no substitute for listening tests. I want to see if it actually proves useful in real world music listening.
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Old 4th February 2011, 04:46 PM   #17
gpapag is offline gpapag  Greece
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Hi Don Hills

Quote:
My original suggestion was all-analog, but it required a scarce part (a 6-gang pot). I'm currently looking for suitable "electronic potentiometer" chips so that I can drive 6 such channels/chips from one physical pot.
Have you thought of using 6 tracking optocouplers instead of the “6-gang pot” ?

When time permits, I have to try a simple version with one optocoupler (per channel) as the variable element of an LP shelve filter. This optocoupler will vary with the same “physical pot” used for varying a volume optocoupler.

Regards
George
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Old 6th February 2011, 11:03 AM   #18
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...
Have you thought of using 6 tracking optocouplers instead of the “6-gang pot” ? ...
I'd need 12 tracking optocouplers, and something to linearise their curves.
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