by kt88pppamp » Sat Jun 15, 2013 3:21 pm
Each transformer is different. One due to inductive properties may cause a motorboat condition and the other may not. I do not know about the cap boards but the original MKIII had called for wiring a ground loop because the main filter cap shared a common ground since they were all in a multi-section can. To eliminate the resulting low level hum, I was forced to install a separate main filter cap.
The cap before the choke must have its own path to ground, or at the very least, you will have a hum. At the worst, you will get a motorboat condition. I never bought the cap boards because I do not trust them (proper grounding was my main concern). I would check the PCB construction to see if the designers routed it properly. If they did not, demand a refund and that they revise the circuit.
Therefore in all my new designs, I never use multi-section caps due to cost and ground loop potential. When I do PCBs, I put the main star point on a large copper pour on the board or even better, route each ground to a terminal strip lug that connects to the chassis.
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