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Old 15th May 2013, 05:16 AM   #1
usul27 is offline usul27  Switzerland
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Default Quad channel volume control

Hi folks,

I've finished and testet the first prototype of my 4-channel volume control. It is designed to be used in my 4-way active speaker project, but can be used for any other project. It features optocouplers for the digital control connection to decouple the circuit from the controller.
It uses a PGA4311 and a OPA1664 input buffer. No output buffer is used, because the circuit should be located near the power stage.

Click the image to open in full size.

Control has been tested from an Arduino and from the RaspberryPi - both work well. I'm thinking about a specific controller board designed just for this project.

Any comments?

Regards
Daniel

http://www.crazy-audio.com

Last edited by usul27; 15th May 2013 at 05:18 AM. Reason: Added signature
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Old 15th May 2013, 09:38 AM   #2
maxw is offline maxw  United Kingdom
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Very nice!

What ICs did you use for opto isolation?
What will you use for a power supply?
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Old 15th May 2013, 10:37 AM   #3
usul27 is offline usul27  Switzerland
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I'm not sure about the power supply. For the tests I'm using a small LM317/LM337 based supply: SimplePower | Crazy Audio. Right now I'm creating a similar circuit with an integrated mains transformer and 100mA LM317L/LM337L which are powerful enough for this circuit (it uses < 20mA).

The Optocouplers are standard KB817 compatible. They are rather slow, but for this application that doesn't matter. Data traffic are only 32 bit per volume change. With the current configuration they should work up to 10-30kHz, but I'm using 1kHz at the moment to be on the safe side.
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Old 20th May 2013, 05:34 PM   #4
usul27 is offline usul27  Switzerland
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Started to code the control software, it is now available on GitHub (link on my site).
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Old 20th May 2013, 06:22 PM   #5
maxw is offline maxw  United Kingdom
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Quote:
Originally Posted by usul27 View Post
Started to code the control software, it is now available on GitHub (link on my site).
The link in your signature doesn't work.
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Old 20th May 2013, 07:07 PM   #6
usul27 is offline usul27  Switzerland
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Thanks, corrected this.
The link to the project site is Quad volume controle, PGA 4311 | Crazy Audio
The Arduino code is here: Controlling QuadVol with Arduino/Sparrow | Crazy Audio
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Old 20th May 2013, 09:27 PM   #7
maxw is offline maxw  United Kingdom
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Quote:
Originally Posted by usul27 View Post
Thanks, corrected this.
The link to the project site is Quad volume controle, PGA 4311 | Crazy Audio
The Arduino code is here: Controlling QuadVol with Arduino/Sparrow | Crazy Audio
Nice one!
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Old 25th May 2013, 08:07 PM   #8
Nisbeth is offline Nisbeth  Denmark
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Very nice, thanks.

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Old 2nd June 2013, 02:43 PM   #9
usul27 is offline usul27  Switzerland
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The final PCB should be here in some days, but at least I finished the power supply :-)
Click the image to open in full size.
Trafopower
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Old 2nd June 2013, 02:44 PM   #10
usul27 is offline usul27  Switzerland
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P.S. Does anybody have an idea, why these images are squeezed?
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