If my memory serves me right, there's a very common mod where you switch out a capacitor and a resistor and it adds a touch more gain and smoothes out the treble a little bit. This was a common mod to the GP-1000's even back in the 90's by Lee Jackson himself, but I know Alexi had his GP-1000 modified I think after HCDR to get a little more bass out of it, which you can definitely hear when they recorded AYDY. Would love to hear what mods the guy from Finland did! I've got an 87 transitional model, an 88 model, and an SP-1000 and I love them all dearly lol.