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NicMac  
#1 Posted : Saturday, April 16, 2011 2:09:16 PM(UTC)
NicMac

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Hi Russ, Brian (and LeonvB),
In the excellent manual of LeonvB, for a dual-mono configuration, i read: "Connect the pin PB1 to GND on the Volumite".
Q: WhyThink ?
I am having some troubles and I will post them if/when I give up solving them on my ownd'oh! or if I locate the problem.............
Cheers,
Nic
Russ White  
#2 Posted : Saturday, April 16, 2011 3:41:54 PM(UTC)
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The reason is because that lets the controller know to controller know you are doing dual mono. :)
LeonvB  
#3 Posted : Sunday, April 17, 2011 4:26:42 AM(UTC)
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The microcontroller has to know there are not 1 but 2 boards (each with their own address) to control. So in a dual mono setup, it can send commands to both boards to set the volume registers.

What problems do you have?
NicMac  
#4 Posted : Monday, April 18, 2011 6:29:29 AM(UTC)
NicMac

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LeonvB wrote:
What problems do you have?


To many unlabeled firmware chips around is one of them :-)

I'm building a dual-mono buffalo where one of my design goals is to have galvanic isolation not only between the controller (which will be in a separate cabinet) but also between the two channels of the DAC.
To isolate the I2C signals I'm using ADUM1250 chips but until now I have not made it work consistently. I think my problems relates to the powering up sequence on the DAC and bus side of the isolators but I'm not sure....



Russ White  
#5 Posted : Monday, April 18, 2011 6:51:35 AM(UTC)
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There is no value in isolating the I2C signal in any case since they should share the same power supply to be sure the controller and the DAC come up at the same time.
NicMac  
#6 Posted : Monday, April 18, 2011 9:44:01 AM(UTC)
NicMac

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They don't share the same supply. Actually there are 28 supply lines (independent secondaries) in the build......
How critical is it that the controller and the DAC come up at the same time?
Would it not be sufficient that the controller come up first?
Happy easter,
Nic
LeonvB  
#7 Posted : Monday, April 18, 2011 10:15:50 AM(UTC)
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Quote:
I'm building a dual-mono buffalo where one of my design goals is to have galvanic isolation not only between the controller (which will be in a separate cabinet) but also between the two channels of the DAC.

The way to do that while isolating the 2 halves would be to power the Volumite from 1 board (and directly attach it using I2C), and isolate the remaining I2C lines to the other board. I doubt however it is worth all the trouble.
NicMac  
#8 Posted : Monday, April 18, 2011 11:40:27 AM(UTC)
NicMac

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LeonvB wrote:
Quote:
I doubt however it is worth all the trouble.

For me it is not trouble - just fun and electronic education!
Russ White  
#9 Posted : Monday, April 18, 2011 1:22:36 PM(UTC)
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Notice I said they "should" share the same supply. My point is that there is no really good way to do otherwise because you will have power up/down sync issues. Plus as long as you are using volumite or the on-board controller there is zero benefit.

Edited by user Monday, April 18, 2011 1:23:23 PM(UTC)  | Reason: Not specified

NicMac  
#10 Posted : Monday, April 18, 2011 2:24:23 PM(UTC)
NicMac

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Anyway, it now works flawlessly (at least for a couple of power on/off cycles).
I'm not expecting a sonic benefit although it might be there eliminating a ground connection between the two channels.
One half of a LCDPS is now powering the Volumite controller and the bus side of the two ADuM chips while the device side of the ADuM's are powered by the BII's. Floating supplies for all three of course.
I will not be using the on-board controller, and hopefully not even Volumite, as I'm still dreaming to soon focus on a controller (AC2, maybe...) located in a different cabinet.
Cheers,
Nic

P.S. The ADuM1250 datasheet says that bypass caps between VD and GND are required. I'm not to worried as it seems to work without. The funny thing is that they suggest caps between 0.1 pF and 0.1 pF.... pretty narrow range and I'm not sure which value to use.
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