So I hooked up my Gould oscilloscope (50MHz analogue bandwidth, not calibrated) and checked a few things out, the circuit looks fine from what I can see.
The picture below could be any random square wave from anything, but it is actually the BCLK signal probed right on the DAC input pin (right on the package). It looks pretty clean. I can not work out why it seems to be running half the speed it should. It seems to be 6.144MHz, I was expecting 12.288MHz. That might explain why the DAC sounded horrid running at what I thought was 48kHz. Half that is obviously 24kHz which isn't ideal for audio! I think it is a software thing (SigmaStudio) as the hardware looks and tests just fine, or I could be calculating it incorrectly..
An electronics engineer and a long term electronics hobbyist. I like tinkering with stuff and making things.