I'm not sure the 33VDC supply will be enough. The resistors and other parts of the circuit are designed for the 48VDC power supply. The power supply is easily available on ebay. Just search for "cisco psa18u-480" on ebay and you'll get many economical choices. As for the hum, I suggest you find out what you did wrong with the CMoy before you try building another amp. Maybe thousands of CMoys have been built without any hum and noise. The CMoy design uses batteries. It's sort of difficult to get hum from a battery.