I recently installed a transformer (12VAC, 2Amp) in a musical
instrument amplifier (rated at 10 Watts RMS), and when I test it with
a variety of input sources (guitars, keyboards, different cables), for
about 30 seconds, the amplifier produces a nice healthy volume level,
and then, consistently, the volume just drops about 50%. For some
reason, this problem sounds like it might be heat-related. Has anyone
else experienced this?

Thanks
Louis