I’m experiencing this exact same issue. The only difference is that it happens to me when I first power on the Firehawk 1500 - thin sound, very thin, almost no volume or drive. It does somehow come back after a while of being powered on (full sound through the speakers). Just started doing this about 2 months ago, after years of flawless use. I love my Firehawk 1500 - perfect amp, but I can’t trust it to perform at the moment. Any solutions or ideas?