Originally Posted by AudioImages
If it's not drive units, and not Comms/Config, then sounds like power amplification to me.
You'll need to remove the back panel complete with associated amplification and DSP and send it off to be serviced.

So, it's definitely not the 861, as the problem recurred, I plugged the 6000s into channels 1/2 and they worked fine.

Next, I swapped the 8000 heads, and the left speaker still displayed the same problems - so it's not the drive units.

Looks like it is amplification / DSP as originally thought. At least now, I believe I've confirmed exactly where the problem is.

Thanks everyone.

Best,
Andrew

Speaker Systems:
1. 2xDSP 8000s, DSP 5500C, 861v4, HD621
2. 2xDSP 6000s, HDMI Switch > Atlona HDMI De-embedder
Headphone Systems:
1. Audeze LCD 3, Stax 009, Chord 2Qute > Violectric 281 > Stax 717
2. Audeze LCD XC, Fostex TH900, Bel Canto Reflink > Chord Hugo > CI Audio Passive Pre, Auralic Taurus
Sources:
Oppo BDP 93 and 83, Project Carbon TT, J River