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Placid HD - Shunt Current - Differs between I2S and SPDIF source
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tdmckellar  
#1 Posted : Sunday, October 8, 2017 5:18:22 PM(UTC)
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I have got my DAC up and running, which consists of a B3, OTTO-II, Sidecar, SPDIF 4 inout board all powered by a single Placid HD.

When powered on, I measure 640mV between TP_VIN+ and TP_CSS+. When I select a I2S source (USB module), I measure 20mV between TP_OUT and TP_SHUNT. However, when I switch to an SPDIF source, the current being shunted jumps to 50mV.

My question is, are these readings okay as they are, or should I adjust the current to a kind of middle ground, as I am aware the recommended current to be shunted is 50mV. I will mainly be using I2S source over SPDIF.

Thank you.
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Brian Donegan  
#2 Posted : Sunday, October 8, 2017 8:28:48 PM(UTC)
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You should adjust the shunt so that it is 50-60mV when playing the I2S source. It will be a bit higher when playing SPDIF, but should not cause any problems.

You will notice that the higher the bandwidth of the material being played, the more current the DAC will consumed. You should choose source material appropriately for setting the shunt headroom.
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tdmckellar on 10/9/2017(UTC)
tdmckellar  
#3 Posted : Monday, October 9, 2017 5:39:49 AM(UTC)
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Thanks for your reply, regarding the source material, would you therefore choose the highest hi-res file type available, ie. 24/192?
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Brian Donegan  
#4 Posted : Wednesday, October 11, 2017 2:42:33 PM(UTC)
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Yes.
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