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Hi all, I have captured two scope measurements at output of Legato. No digital inputs at BIII. No load at Legato Outputs. USB cable is disconnected. Measurement at SE output (7 mV, 200 kHz):  Measurement at Balanced ouput (34 mV, 200 kHz):  Noise is exactly the same on both channels. Some idea what's the source of this noise? Regards, Luis. Edited by user Sunday, April 7, 2013 8:22:31 AM(UTC)
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Hi Luis..
Are you using the updated AVCC shunt module ?
Try taking a measurement at the ACVV output pin. Careful - don't short anything ;-)
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Originally Posted by: avr300  Hi Luis..
Are you using the updated AVCC shunt module ?
Try taking a measurement at the ACVV output pin. Careful - don't short anything ;-) SRA2 v1.0 Measurements at Outputs: DVCC: Sinusoidal 1.9 MHz, 14 mV signal.  AVCC: sawtooth signal, 250 kHz, 118 mV 
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I think your AVCC shunt is oscillating. As pr. Russ: "If you have a couple 100-220pf caps try putting one across each -IN and OUT of the dual opamp on the AVCC.This makes the module very stable and more immune to instability that can be induced by RF/EMI etc." Before upgrading to the new version I did it to my version 1.0. The attached picture shows where to insert the caps. Picture shows non-cleaned development stage, sorry for quality. avr300 attached the following image(s):  IMG_9803.JPG (85kb) downloaded 64 time(s).You cannot view/download attachments. Try to login or register.
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avr,
It seems that you have had same problem.
Seeing your picture capacitors seems ceramics.
Regards.
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Those was what I had at the very moment.
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and perfectly well suited of this task. :)
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I have added two wima 100 pF MKP capacitors, I don't have ceramic caps at home. AVCC out is clean now !  DVCC is the same that before: a 14 mV sinusoidal noise.  How to fix this noise at DVCC output? Is it worth the effort? or have no efect over quality sound? Regards, Luis.  Uploaded with ImageShack.us
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If its the older trident, the best bet is to upgrade. But it really should not impact things very much.
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Originally Posted by: luismc DVCC is the same that before: a 14 mV sinusoidal noise. How to fix this noise at DVCC output? Is it worth the effort? or have no effect over quality sound? Regards, Luis. DVCC is the Digital side of the power supply arrangement. It's not used for the AVCC shunt. I wouldn't do anything there. Good work on the AVCC.
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hi avr, If DVCC is not used, why is it connected to DVCC DAC module?  luis
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He was saying it is not connected to the AVCC module. :) It is there as an optional voltage reference or relay trigger for power synchronization, but the AVCC module does not use it. Edited by user Saturday, April 13, 2013 2:04:11 PM(UTC)
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