[Veltliner]

I just took a new 1 Tb G-Tech G Drive Q into service.

It's constantly running, even if nothing is copied to it. Constant scratching noises.

My old G-Tech (500 Gb) spins down after copying things to it and is quiet as a mouse.

What could be the reason?

It can't be copying in the background as I'm not using Time Machine with it.

[reader50]

Idle spindown is up to the case's controller. Some (like oxford) are good, and allow spindown. Others just run the drive endlessly.

[Veltliner]

My other G-Tech ( a bit older) spins down.

The new one's doesn't. It has an Oxford chip set.

[Veltliner]

It has an Oxford 934 chip set.

[reader50]

My old PATA FW enclosure has an oxford 911+, it spins down. The other enclosure is a USB/esata with generic chipset, which I haven't used enough to notice.

Check with G-Tech, see if there is a firmware update available? It might be worthwhile to check the Oxford site for firmware too.

[Veltliner]

There is a software on this external hard drive that helps you enable Time Machine. Maybe it's the culprit, keeping the drive busy (even though I didn't enable Time Machine).