From f73780ad2d00eb1ca8ffd302a4fa74e4459c40cb Mon Sep 17 00:00:00 2001 From: drowe67 Date: Sun, 21 Sep 2014 08:41:56 +0000 Subject: [PATCH] added change log entries for U8 bypass and ADC1 & 2 series resistors to remove static clicks git-svn-id: https://svn.code.sf.net/p/freetel/code@1846 01035d8c-6547-0410-b346-abe4f91aad63 --- smartmic/SM1000-C/Change-Log-C.txt | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/smartmic/SM1000-C/Change-Log-C.txt b/smartmic/SM1000-C/Change-Log-C.txt index 794ce6ab..aad5d3bf 100644 --- a/smartmic/SM1000-C/Change-Log-C.txt +++ b/smartmic/SM1000-C/Change-Log-C.txt @@ -211,7 +211,7 @@ renumber to correct for duplicate #31 RGB 9/8/14 I see your point though, change would aid assembly. Status: Will change part footprint & PCB. -42. [] added 3n9 between U8 p3 and ground +42. [] added 3.9nF between U8 p3 and ground + removed some tonal noise and Status: No action taken - What is 3n9? Will add. @@ -293,7 +293,11 @@ Status: Researching effect on TPS54329E SW PS chip. RGB 09/15/14 58. Nice tactile feeling switch for PTT (like power switch, put perhaps not locking?) -59. 1nF on ADC1 and ADC2 inputs close to uC. While debgugging noise I found big spikes and ringing when the ADCs sample. I think it's the inability of the op-amps to drive high frequencies. These caps removed the ringing, but made no apparant difference to the noise. However I think they are useful as a precaution to reduce the general level of noise on the board. +59. 1nF on ADC1 and ADC2 inputs close to uC. But DNL for now. While debgugging noise I found big spikes and ringing when the ADCs sample. I think it's the inability of the op-amps to drive high frequencies. These caps removed the ringing, but made no apparant difference to the noise. However I think they are useful as a precaution to reduce the general level of noise on the board. + +60. 1500 resistor between ADC1 and ADC2 and outputs from op-amps. After much experimentation these were found to reduce the static type clicks being produced by ADC to acceptable levels. + +61. LM386 power supply bypassing to remove switcher "washing macine" type noise from ouput audio. 4.7 ohm (rated at 200mA, IIR=0.2W) between VIN and pin 6 U8. 220uF electrolytic between pin 6 and GND. Both placed near U8. Questions: 1. SM1000 designed to be operated with 6-16V power supply. Would should recommend 9-15V. Should we recommend PS? Many will operate at 13.8V(rig supply). Do we risk ground loops, etc. using rig supply? -- 2.25.1