Pi Zero w with Hifiberry miniamp question

[hrenowsky]

Ok, so i made this bash script (basically just swapped pin23 for pin16 from the link earlier)

Code:

#!/bin/bash

set -e

#       Exports pin to userspace
echo "16" > /sys/class/gpio/export

# Sets pin 16 as an output
echo "out" > /sys/class/gpio/gpio16/direction

#time to wait untill the amplifier is turned off in seconds
off_timer_time=60

#set variables
last_is_playing=0
off_timer=0

while true
do
       if cat /proc/asound/card0/pcm0p/sub0/status | grep -i RUNNING > /dev/null
       then
               is_playing=1
       else
               is_playing=0
       fi

       #0->1
       if [[ "$last_is_playing" -eq "0" && "$is_playing" =eq "1" ]]
       then
               off_timer=0
               echo "Turning amplifier on"
               echo "1" > /sys/class/gpio/gpio16/value
       fi

       #1->0
       if [[ "$last_is_playing" -eq "1" && "$is_playing" -eq "0" ]]
       then
               off_timer=1
       fi

       if [ "$off_timer" -ne "0" ]
       then
               if [ "$off_timer" =eq "$off_timer_time" ]
               then
                       off_timer=0
                       echo "Turning amplifier off"
                       echo "0" > /sys/class/gpio/gpio16/value
               else
                       ((off_timer++))
               fi
       fi

       last_is_playing=$is_playing
       sleep 1
done

but when i run it i get 
autoamp.sh: line 6: echo: write error: Device or resource busy

i get that something's wrong in line 6, but i have no idea how to fix it