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compression/ downward expansion audio or rf influence?

K4EAR
K4EAR Member ✭✭
edited March 2017 in SmartSDR for Windows
I like to use an external mic preamp and rack gear, as the compression/expander function seems too aggressive for my tastes with 1.05. Does any of the onboard processing happen in the RF domain or is it in the audio codec before the IPA/PA? What is the recommended max input for the rear panel jack? I feed -10dbm and the COMP level at 0. It seems the compression/downward expansion fight each other. Maybe in 1.1 we can have more control over this.

Answers

  • Tim - W4TME
    Tim - W4TME Administrator, FlexRadio Employee admin
    edited March 2017
    It is all in the DSP. The audio input device in the FLEX-6000 series radios is designed for a “consumer line level” specification. This is defined as -10 dBV. If you plan to use “professional line level” (+4 dBu) devices to feed your radio, you will need to reduce the output level so that it does not exceed the -10 dBV level. The hardware input will clip around 0 dBm. I use a mic preamp and it is set for 0 dB on voice peaks. In SmartSDR, the +20 dB boost is turned off and the mic gain is set for 10, which shows 0 dB on voice peaks. Since I am not using an outboard compressor, I have compression on at a setting of 50. The compressor is actually a compander with a downward expander. If you are using very low levels of compression, the action is mostly going to be downward expansion.
  • G4BIM
    G4BIM Member
    edited January 2015
    Hello Tim This kind of information is very useful indeed, thank you. I am using the 6700 with an Optimod 9300 Digital audio processor. The two units seem to be working fine together, but I would be grateful for any comments or guidance from you. Kind regards Peter G4BIM
  • K4EAR
    K4EAR Member ✭✭
    edited April 2014
    In the next generation of hardware go to AES/EBU and S/PDIF options for input options :-)
  • G4BIM
    G4BIM Member
    edited January 2015
    Agreed.....

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