Unfortunately, some drives and devices can’t draw enough power when using this adapter. The best part? It’s complete pot-luck unless you know the power requirements for your devices off-hand. Apple does state it will provide power for devices that need up to 7W but that information may not be easily identified on your drive or audio interface. I had a look at the G-Technology drives and can’t for the life of me find anywhere on their site that lists their bus-powered drive’s requirements.
Whilst investing in new Thunderbolt or USB3 devices will ensure compatibility, if you’re workflow comprises of using perfectly good FW800 drives then be prepared to lug around a power adapter and hope you’re not going to work in the field.