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Russ White  
#21 Posted : Sunday, February 20, 2011 7:15:21 PM(UTC)
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Nothing on the DAC side of things. :)
kpavey  
#22 Posted : Monday, February 21, 2011 4:44:07 AM(UTC)
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OK, pics at last...and some notes

* Preliminary layout until I fit everything in (HiFace USB to replace dddac.de USB-I2S and Tent Clock modules) powered by its own bridge and 15kuf Jensen 4 pole capacitor - unregulated (and probably should be)
* Extra rectifier bridge not used - a carryover from the last project
* Lundahl 1527XL transformers - wired in parallel each side to reduce op impedance (not that relevant to this issue)
* Placid installed today (old version) - set to around 327mA and 5.5V
* Note - despite the switch on the PSU (Brian suggested I add to ensure the firmware/Vol and Buff 2 were synced) and the Placid supply the Volumite still doesn't work properly
* Automute LED is now not on and lock is - which is normal. (Flash makes it look like Automute is lit but it is not)
Buff 2 Pics - initial implementation

Did this help troubleshoot things? Cheers.

Edited by user Monday, February 21, 2011 4:47:16 AM(UTC)  | Reason: Not specified

NicMac  
#23 Posted : Monday, February 21, 2011 10:22:01 AM(UTC)
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Haven't you wired the positive supply line (usually red) to the GND pad in stead of VCC on Volumite?
Cheers,
Nic

EDIT. No - it seems wired the same (red = GND) on Buffalo.

Edited by user Monday, February 21, 2011 10:27:39 AM(UTC)  | Reason: Not specified

avr300  
#24 Posted : Monday, February 21, 2011 2:10:08 PM(UTC)
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kpavey - do you have access to an oscilloscope ?
kpavey  
#25 Posted : Monday, February 21, 2011 2:25:46 PM(UTC)
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Hi AVR

Yes I have an old ex Saudi Airforce Tektronics 475 CRO. A couple of broken knobs but she works OK. What did you have in mind?
avr300  
#26 Posted : Monday, February 21, 2011 2:34:24 PM(UTC)
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I once had similar problem. It turned out that it was a faulty (programmed) Atmel.

Try to measure the digital lines. SCL will continuously send a clock signal. SDA will continuously send the digital representation of the pot position. In other words, both lines will be "live" all the time.
kpavey  
#27 Posted : Monday, February 21, 2011 3:50:24 PM(UTC)
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Thanks for the tips AVR

Is the clock signal the same as BCLK? I guess it's unlikely to need to be anywhere near that fast.

Followup - can only measure what I'd describe as noise - 50-200mV max, period around 1us, generally sinusoidal but nothing constant and repeatable like you'd expect a clock to be. Similar rubbish on both SDA and SCL.

Then....

I was swapping in my valve preamplifier late tonight, and went to try the Volumite on the odd chance it would work. And now it does. I did NOT change anything in the DAC at all, I left it on whilst changing out front end preamplifiers. Very odd. Hopefully it stays this way. Hmmmm. The pot is not that linear in its response, seems like a 30dg turn from full on takes out 85% of the volume. I assume that's normal?

Edited by user Tuesday, February 22, 2011 5:17:39 AM(UTC)  | Reason: Not specified

avr300  
#28 Posted : Wednesday, February 23, 2011 10:30:11 AM(UTC)
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It's normal. It's not implemented linear, but logarithmic.
kpavey  
#29 Posted : Thursday, February 24, 2011 8:00:48 AM(UTC)
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But.the pot IS linear right?
avr300  
#30 Posted : Thursday, February 24, 2011 8:20:54 AM(UTC)
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So it say in the BOM.

"5K Linear"
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