I see, that makes a lot of sense! Only one question: the pin header outputs constant 12V? So, no control at all even on DC (3-pin) fans? Because in that case, I'd get the PWM, too. But if it meant losing fan control, I'd prefer an actual DC fan whose RPM can be controlled by the miner. No reason to 'over-cool' the hashboard, if there's more noise reduction to be had, right?
It seems the miner only outputs 12v, with no control on the voltage.
You could use the
Noctua NA-FC1 (link) to control the fan speed of a PWM fan.
I didn't play with the fan speed, but at 525MHz, you'll need the fan at full blast to cool it properly.
With the Noctua NF-A8 PWM and at 525MHz, the heatsink is at 55°c; you can barely keep your finger on it.
You'll probably need to lower the frequency, to lower the fan speed.