Leave that GND alone.
Mine is in an aluminum enclosure, and the safety Earth at the IEC inlet connected to the chassis too.
I used to have the GND by the pot connected to chassis and that had introduced considerable level of noise from the ground loop, as I use the amp at work and it takes signal from a sound card line-out in a PC. I could hear everything from hard drive transients, things moving on the display monitors, mice crawling, and CPUs working their ashes off on something heavy....So I lifted it and it became as quiet as vacuum can be. See the dangling lug in the pic. The safety ground to the chassis wiring was never removed though, by the way.
That dangling GND could also be grounded to chassis through a resistor of, say 10R or 47R, without ground loop noise penalties but I didn't bother.
Mine is in an aluminum enclosure, and the safety Earth at the IEC inlet connected to the chassis too.
I used to have the GND by the pot connected to chassis and that had introduced considerable level of noise from the ground loop, as I use the amp at work and it takes signal from a sound card line-out in a PC. I could hear everything from hard drive transients, things moving on the display monitors, mice crawling, and CPUs working their ashes off on something heavy....So I lifted it and it became as quiet as vacuum can be. See the dangling lug in the pic. The safety ground to the chassis wiring was never removed though, by the way.
That dangling GND could also be grounded to chassis through a resistor of, say 10R or 47R, without ground loop noise penalties but I didn't bother.
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I've just done the maths on the choice of relay and its series resistor and both are very poorly chosen in this kit.
I'm using a 15-0-15V transformer which gives me an unregulated DC voltage of approx 21V DC for the relay.
Rather than attempt to unsolder the 5V relay I have simply replaced the 200R series resistor with a 560R 1W resistor. (actually 2 x 270R 0.6W in series).
Where the original designer got 5V relay and 200R from beats me. Thge relay would have approx 9V across it and the resistor would have been right on the limits of its maximum dissipation ?
I'm using a 15-0-15V transformer which gives me an unregulated DC voltage of approx 21V DC for the relay.
Rather than attempt to unsolder the 5V relay I have simply replaced the 200R series resistor with a 560R 1W resistor. (actually 2 x 270R 0.6W in series).
Where the original designer got 5V relay and 200R from beats me. Thge relay would have approx 9V across it and the resistor would have been right on the limits of its maximum dissipation ?
This kit seems incredibly sensitive to mains pick-up.
With no input connected it is dead quiet. I use it as an amplifier for my laptop which has no mains earth connection. The amplifier itself also has no mains earth connection to 0V.
If I connect an open ended input to the board I get a faint, but acceptable, mains hum.
As soon as I connect the interconnect to the laptop the mains hum increases significantly. It's tolerable when the source volume is high but unacceptable with a quiet source.
With no input connected it is dead quiet. I use it as an amplifier for my laptop which has no mains earth connection. The amplifier itself also has no mains earth connection to 0V.
If I connect an open ended input to the board I get a faint, but acceptable, mains hum.
As soon as I connect the interconnect to the laptop the mains hum increases significantly. It's tolerable when the source volume is high but unacceptable with a quiet source.
It's quite common to get low level power supply and PC system noise when you couple to laptops via standard 3.5mm jacks or even via a USB > External DAC connection. PCs are generally even worse on noise because the inherent mains ground loop with most power amplifiers can make matters much worse. For lowest possible noise, I use an external DAC with the addition of a standard USB > OPTICAL adaptor from the PC/Laptop in stubborn cases. Sure, the arrangement is messy and means yet another gadget to go wrong but at least it works very quietly - or 3 set-ups that I occasionally use, have worked quietly for several years.
You're not alone in criticising your kit from a builder's point of view either. My TPA6120 kit may be a little different to yours but still the corners are cut everywhere on parts and layout. IMHO, even though they are neatly laid out and look professional and competent boards, the kits I have looked over, really need a lot of re-working and of course, finishing off with a properly designed case and separate PSUs to bring them up to expected datasheet performance level.
You're not alone in criticising your kit from a builder's point of view either. My TPA6120 kit may be a little different to yours but still the corners are cut everywhere on parts and layout. IMHO, even though they are neatly laid out and look professional and competent boards, the kits I have looked over, really need a lot of re-working and of course, finishing off with a properly designed case and separate PSUs to bring them up to expected datasheet performance level.
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