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Joined: 6/30/2021(UTC) Posts: 3 
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Setup: Placid HD (100mA Shunt), Legato (multichannel custom gain 600/2700) I was trying to get the most lenear phase response on a custom gain Legato and I was trying different caps and values, when I noticed that after power on I get widely different phase angles. Pulled my hair out with the cap combinations. Bottom line: When I hold the reset pins when powering on, and release reset pins after 5 sec. Everything is perfect. I think the reset should come out of low only when all analog stages in the DAC are fully active and set. Clearly there is not enough delay in the firmware before everything analog is settled. I really would like to avoid adding a micro controller just so I can introduce a start up delay (hold reset closed for ~sec). I think for those who use the BIII as a stereo dac this may never have been a concern, but in multichannel mode if your crossover points are in the effected region, this is a problem. all other measurements THD, THD+N, IMD, Magnitude, Noise Spectrum etc...are all in line with expectations it is only phase. Not sure what firmware version I have the board is 2014 vintage. See attached image, the curves bellow 10deg @40k are the once with rest pin shorted on power on then released after 5 sec. The correct response.  BIII Power On Phase Issue.PNG (187kb) downloaded 6 time(s).Edited by user Wednesday, June 30, 2021 6:41:31 AM(UTC)
| Reason: Added comment on other measurements
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Rank: Member
Groups: Member
Joined: 6/30/2021(UTC) Posts: 3
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Turns out removing the firmware results in the same issue. So it is not firmware or my firmware does nothing.
Also tried IVY-III same exact problem.
Tried powering IV boards first then the DAC PSU, same problem.
Measured the Trident regulators they report 3.27, 3.27, 1.17.
This will make it rather difficult to build a 4 way system with xo points with widely different phase depending on what happens at power on.
Any help ideas much appreciated.
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Rank: Member
Groups: Member
Joined: 6/30/2021(UTC) Posts: 3
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Well, I was using the SPDIF transceiver module to test different configs,. in pure frustration trying to get to the bottom of all this, I swapped the SPDIF board with a MiniSHARC, It seems to produce solid phase response with every power cycle or reset, but I think its about the fact that the MiniSHARC takes a few seconds to boot and provide sync. Clearly indicated by the LEDs on the buffalo, So I think this just "masks" the issue by adding delay in the boot process... So, does anyone have a firmware that implements a hold reset for a few seconds? As I said I am trying to avoid adding an arduino or some other micro controller to do this. Edited by user Friday, July 2, 2021 9:12:37 AM(UTC)
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