9500.0Hz peak with stereo input and other annoying noise

[eapo]

My PiFmRDS emits a really annoying 9500.0Hz peak and other lower noises when the input has more than 1 channel (and i really want stereo!).

• 9500.0Hz peak spectrum

Reducing the channels to 1 (-c 1) solved the high peak, but still noisy:

• 1 channel, still noise spectrum

Went trough the necessary preemphasis (Issue #50) problem, but still not satisfied.

Here is my actual command with a lot of hacks:
sox -S http://ice1.somafm.com/suburbsofgoa-128-mp3#.mp3 -c 1 -t wav - firfit ~/75usPreEmphasis.ff speed 2 | sudo ~/PiFmRds/src/pi_fm_rds -freq 107 -audio -

Acting the same with different sources and different -freq and even with different DEVIATION, the noise is still there.

Really wish to use this amazing app. Thx for your effort (where is your donation link?) ;)

---

$ cat /etc/os-release
PRETTY_NAME="Raspbian GNU/Linux 9 (stretch)"
NAME="Raspbian GNU/Linux"
VERSION_ID="9"
VERSION="9 (stretch)"

$ uname -a
Linux raspi_valto 4.14.79-v7+ #1159 SMP Sun Nov 4 17:50:20 GMT 2018 armv7l GNU/Linux

$ cat /proc/cpuinfo
Hardware        : BCM2835
Revision        : a020d3

[etiennedemoulin]

Maybe your Raspberry's power supply isn't powerful enough? (2A is good)
If you don't have, you can add the line gpu_freq=250 to the /boot/config.txt file.
Let us know