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audiovolume

Radio audio volume

ULARI audio input and output is served by microprocessor audio ADC/DAC peripheral and a proper analog frontend. Audio settings in Armbian Linux are controlled by ALSAmixer application. Let's issue a command:

root@nanopiduo:~# alsamixer

Signal levels in ALSA mixer

OK, so we are only going to touch options which are important for us, these are:

  • “Lineout volu” (Lineout volume control) - this controls the audio output signal level (from ULARI to radio). Lowest values result in a signal of about few milivolts (do not use levels 0 and 3 as they are really no signal according to my oscilloscope). Highest values result in a signal of more than 1Vpp.
  • “ADC input ga” (ADC input gain ctrl) - this controls the audio input amplification (from radio to ULARI). Do not set it too high or your audio signal may be clipped and decoding will work very poor (TODO: check exact signal amplitudes for each level).
  • “MIC1 boost A” (MIC1 boost AMP gain control) - this also controls the audio input amplification (different stage), but this value is hardcoded in kernel settings and will restore every time to the same value, better do not touch!

Audio output levels for different Lineout volume control values:

  • 10 - 30 mV
  • 23 - 52 mV
  • 32 - 84 mV
  • 42 - 134 mV
  • 52 - 218 mV
  • 61 - 364 mV
  • 71 - 592 mV
  • 81 - 1000 mV
  • 90 - 1620 mV
  • 100 - 2740 mV

Every change will immediately be visible in real analog level. After setting these values to desired levels we can save them to nonvolatile memory using command:

alsactl store
Different radios need different audio levels (from ULARI to radio) for proper operation. Especially radios with MINIDIN 6-pin DATA connector need it around 40mV, some of them will even not key the PTT if audio signal level is higher than acceptable.
Different radios provide different audio levels (from radio to ULARI). Especially, when you are using an audio signal from speaker output and your radio has a volume knob, then do not set the knob above 1/3 of the scale because this signal level is often good enough and higher levels can cause signal clipping.

What's next

Now we need to take a look at Ulari-manager configuration.

audiovolume.txt · Last modified: 2019/02/27 15:45 by sq3plx