Multiple circuits on one supply

[Taylor]

So I haven't done much with DIY circuits in a couple of years, and I've forgotten a lot. A few questions:

I built a preamp and an 8 watt power amp (kits), and I want to run them off of the same power supply. The pre is 9volt, the power amp says it can use between 9 and 15 volts. What do I need to do to run them off of the same supply? Anything more than connecting the + and - leads of the supply to both? Will the poweramp have less wattage at 9 volts? Would it be better to run the poweramp at 12v, which is recommended, and step the power down to 9v for the pre? Also (this is embarassing), what do I connect the ground to? I can't remember if you just solder it to the enclosure or what.  Is it necessary to connect the ground to get the circuit to work (that is, while this circuit is not boxed up, can I leave the ground pad not soldered to anything)?

[axg20202]

So I haven't done much with DIY circuits in a couple of years, and I've forgotten a lot. A few questions:

I built a preamp and an 8 watt power amp (kits), and I want to run them off of the same power supply. The pre is 9volt, the power amp says it can use between 9 and 15 volts. What do I need to do to run them off of the same supply? Anything more than connecting the + and - leads of the supply to both? Will the poweramp have less wattage at 9 volts? Would it be better to run the poweramp at 12v, which is recommended, and step the power down to 9v for the pre? Also (this is embarassing), what do I connect the ground to? I can't remember if you just solder it to the enclosure or what.  Is it necessary to connect the ground to get the circuit to work (that is, while this circuit is not boxed up, can I leave the ground pad not soldered to anything)?

If the preamp is made with components that are rated well above 9v you should be able to run it at a higher voltage than 9v without any problems - eg. you could run everything at 12v as you suggest if the components are rated at 16v and above. As for ground, you need it connected to something to complete the circuit. Best bet would be to have ground connections from the two circuit boards coming to single ground point e.g. the shield of the input jack. Connect the power input ground to here too. This all assumes that the circuits are both DC (not AC) and they both only require a positive voltage (some amp circuits require bipolar power e.g. +xV, -xV and ground).