Grounding loops of chips on shared heatsink ?

[MathWizard]

I'm building a 5.1-channel stereo, on proto-type boards, with some TDA2030A AB-class audio amps. So far I have a main PWR board w/ Gnd rail, and made a star grounding w/ each little board (inputs/preamp/driver-outputs) having 1 GND branch into.

As for the 6x TDA2030 output chips, their tab is on the negative supply, so for me that's just GND. And I put them all on 1 great big aluminium heatsink, w/ thermal compound. So it's probably not even a good GND connection really.

Each TDA2030 still has it's own gnd wire, back to the driver boards (3 boards, for L/R, RL/RR,Center/woofer)

looks about like this


So should I be isolating them from the shared heatsink or not, the shortest signal path and lowest impedance should still be back to the originating driver/output board ?

The only mains earth connection, is on the input jacks from the computer, power is from a non-grounded transformer.

[wraper]

Tab is connected to -Vs, not GND. It's just a negative power pin as far as you should be concerned. What matters is no ground loops in input and feedback circuit. But I do not suggest using it to begin with. It's no longer produced by ST. What you can buy are knockoffs of different level of crappiness. Not it was that good to begin with.