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#1 Posted : Thursday, March 31, 2016 9:58:30 PM(UTC)

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20160319_164638.gif (296kb) downloaded 12 time(s).Hi all,

I have a dual-mono configuration of Opus DACs controlled by software with arduino I2C. I have a OTTO switch also controlled by arduino to switch from PCM to DSD coming from the amanero USB.

The sound is better described by music in the background and with a lot of noise. Before getting to the DACs the PCM signal is upsampled by a metronome upsampler.

Without connection to an amplifier, in the outputs of the DACs (one for the left and other for the right channel) I have consequently in the ventus EZ:

0.115 to 0.120 vdc in the output of both ventus
0.125 vdc in In+
0.025vdc in In-

With no music and connected to the pre I have:

0.065 vdc in the output of both ventus
0.000 vdc in In+
0.053 vdc in In-

I also have the CC1 installed in both ventus for my XLR to RCA conversion. Don't know if this is correct and I hear some little noises in the speakers with no music playing. Should i remove CC1 from the ventus?

I tried to input a DSD signal through the USB amanero. In the speakers sounded music also with a lot of noise. At the same time I checked the OTTO switch voltages and there was 3.3vdc on the DSD data output side but the PCM output side of the OTTO also had voltages around 1.6 vdc for clocks and 1.2vdc for data pin. Is this normal? shouldn't the output (for the PCM side) be zero with DSD signals?

I have arduino outputing 5V to OTTO's S pin when DSDON pin from amanero is 3.3Vdc but something seems wrong with the switching. I also have a shunt from OE to GND in OTTO and R1, R2 and R3 installed. What are your thoughts?

What might be the problem?

Edited by user Saturday, April 2, 2016 5:32:01 PM(UTC)  | Reason: Attached an image

Brian Donegan  
#2 Posted : Monday, April 4, 2016 2:24:26 PM(UTC)
Brian Donegan

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The noise you are hearing is most likely clock noise injected into your power supply wiring from nearby I2S data lines.

In the center of your picture, you can see these wires overlapping.

You should minimize the length of your I2S wiring, and keep it well away from the power supply wiring.

I suggest stacking the Metronome (and spinning it around) over the Opus DACs, which would make the I2S lines significantly shorter and keep them from crossing over the power lines. I woudl also move the OTTO and possibly Amanero closer to the DACs, again, to minimize the I2S/DSD line lengths.

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