So the Yamaha PM2000 is one of the only non-consumer products to use The Hitachi Corp HA1457 Chip. It was a very HiFi chip in it's day. It uses a dual rail +- 24VDC power scheme and it is clean reliable and has headroom for days. The down side is the rather cool but rare SIP package. So a replacement that plugs right in ain't out there. But time marches on. The TI OPA604 chip uses the same power scheme and has much better noise and linearity specs. So it is really a toss up. But I think to my ears the OPA604 is worth the time to replace. Yes I had to design my own PCB to make this work.