O/A 'sound advice' needed

The gauges on my regulators arn't too accurate at lower pressures so if I set them for a size 1 or 2 tip (3.5 psi / 0.24 bar) I don't quite get enough gas flow so have to increase the pressure at the regulators to get a decent neutral flame, the problem is I get a low hum from the mixer or nozzle, is this normal ?
As you can guess I havn't been at this long ! The welds come out just fine though but I'm a tad nervous about operating like this for any length of time.

Thanks in advance
Jim
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