I had the 990 & 991 power amps and the only difference internally is that the 991 had balanced inputs... All other parts are exactly the same. I have both schematics and they are EXACTLY the same other than the fake heatsinks on the 1080 & 991. The 1080 I believe has the 12V trigger circuit as well.
Soundwise 990 & 991 sound exactly the same.... 1080 is probably very close if not the same....
I hope this helps...
Dan
Soundwise 990 & 991 sound exactly the same.... 1080 is probably very close if not the same....
I hope this helps...
Dan