Loud click on startup

[apmcpherson]

This has been around since the beginning, but it would be nice to squelch it. When you start a program, there's a loud click at the audio outputs. It is related to the codec, not the speaker amps. I think it could be silenced through a different order and timing of I2C initialisation.

[TheTechnobear]

yeah, this makes you jump if you have bela connected to a mixer, which then goes to your monitors :)
(there seems to be a much softer one when the patch stops too, you can hear it best, if you use a silent patch like 'scope')

[giuliomoro]

diff --git a/core/I2c_Codec.cpp b/core/I2c_Codec.cpp
index 70197ed..f22b9a2 100644
--- a/core/I2c_Codec.cpp
+++ b/core/I2c_Codec.cpp
@@ -117,6 +117,7 @@ int I2c_Codec::startAudio(int dual_rate)
        if(writeRegister(0x66, 0x02))   // Clock generation control register: use MCLK, PLL N = 2
                return 1;

+       usleep(10000);
        if(writeRegister(0x33, 0x0D))   // HPLOUT output level control: output level = 0dB, not muted, powered up
                return 1;
        if(writeRegister(0x41, 0x0D))   // HPROUT output level control: output level = 0dB, not muted, powered up

This would get rid of MOST of the click at startup. There is still a quieter tick after the usleep, which seems to be the same that you get when a silent patch stops.

[apmcpherson]

A quiet tick is much better than a loud pop! I'm not sure there's much that can be done about that either -- e.g. Mac laptops do the same thing when audio is turned on or off. The only alternative might be to leave the headphone amp powered up all the time, regardless of whether a program is running, but that might have other drawbacks.

[giuliomoro]

I tried to set the headphone level to 0 and mute the DAC before powering up the HPamp, but it makes no difference: that small click is still there.

If someone wants to get rid of this, then they probably also want to use the line output instead of the headphone output.
Not sure what it sounds like from the line output?