Kontrol S4/Mac Audio Routing

Evening all,

I've finally switched my venerable PC desktop to an iMac (2009), but still retaining the Win7 lappy for gigs.

I'm new to MacOS but very familiar with troubleshooting PC audio routing, and I've done the usual search for topics regarding Mac/S4/Audio/Routing however I can't quite find the solution to what seems a simple audio routing setup. For late evening (i.e. no monitor use) broadcasting purposes I tend to use the following routing (Win7):

S4 USB Port > PC USB2.0 Port
S4 RCAs > 3.5mm jack PC Soundcard input i.e. line in
PC H/Phone Out (3.5mm jack) > Headphones

In terms of Audio Setup in TP2: Audio Device set to 'Traktor Kontrol S4' and the Built-In Soundcard set to 'Kontrol S4 WDM Audio' i.e. shared.

This results in a lovely blue speaker icon at the top of the TP2 window.

Basically with the Win7 setup listed above I'm able to control/play audio in TP2 from the S4 to PC Line In, broadcast this input, and monitor the output from the PC headphone output... lovely jubbly, happy Backtothefront

So forwarding on to the Mac:

I've set up the physical connections similarly to the PC config above i.e.

S4 USB > iMac USB Port
S4 RCAs > 3.5mm jack to iMac Line In
iMac Headphones Out > Headphones

Within TP2 the Audio Device is set to Kontrol S4, however the speaker icon at top of the TP2 window is orange which obviously identifies a audio routing problem. I've checked within Sys Prefs in MacOS which is seeing an audio signal correctly to Line In however I cannot hear any audio out of the Mac built in speakers/headphones (when connected). Within TP2 itself the audio appears to be playing correctly, with exception of the 'orange lit speaker icon'.

If I switch the Audio Device to 'Built-In Core Audio' then the icon goes blue and I can now hear the tracks playing over the Mac speakers/headphones. In this situation however the hardware Main Vol knob has no effect on the output volume from TP2, which I know is independent from the 'inside TP2 Main Vol'. This essentially means the output I can hear is the audio via USB as opposed to the S4 RCA output which is what I'm after.

I've been through the MacOS utils to see what I can change audio wise without any luck. I suspect this is just a case of how it works, but I wondered if anyone had any solutions to being able to use the actual S4 RCA Audio Output through the Mac for broadcasting and monitoring purposes.

I hope I've explained it so it can be understood, thanks in advance, it is appreciated.

Cheers,

BTTF