The audio analyser pope owns already outputs + 20 dBu (11 Vpeak) which can be generated by using ± 15 VDC rails.
As pope needs signals with higher values, a low distortion PA (<> Class C) needs voltage rails above the 15 VDC mark.
With ± 22 VDC (max value for most opamps), 17 Vpeak (24 dBu) can be obtained, best case. That is just 4 dB more that the analyser.
For more output voltage, amplifiers that accept higher voltage rails are required.
By pushing the LM1875 that trobbins suggested to its' limits (so 60 VDC or ± 30 VDC supply), 24 Vpeak (27 dBu) should be possible : a 7dB improvement.
But pushing a PA to its' limits always raises distortion.