I have a small Roland amp and an rd600 keyboard. I’ve tried hooking the keyboard to the Roland amp several ways. With just the L mono. I tried both r and l mono. There’s 2 different r and l monos I haven’t tried them all at once. I tried the phones input on the keyboard to every input to the amp. Nothing. My computer speakers work if I use the phones input on the keyboard with a 1/8” to 1/4”. But I wanted to use an amp. Does anyone have an rd600 and understand what I’m saying?