原文是
M³ as a pre-amplifier
The low-noise performance and moderate voltage gain of the M³ also makes it an excellent line-stage pre-amplifier. The ultra-low output impedance allows the M³ to drive a very long interconnect cable without loss of quality. Since a pre-amplifier's primary function is to switch among multiple input sources, just add multiple input jacks and a selector switch. To minimize noise and crosstalk, mount the selector switch as close to the rear panel input jacks as possible, and use a shaft extension kit (with couplers and panel bearings) for the front panel knob. For example, see the shaft accessories from Ocean State Electronics.
If the M³ will serve strictly as a pre-amplifier (which would be used to drive an outboard speaker power amplifier), then the output ground channel can be left unpopulated (i.e., all parts with designations ending with a G-suffix). The pre-amplifier output jacks should have its ground connected to the IG pad of the M³ board, not the OG pad. The easiest way to do this is to wire all the input jack grounds and preamp-out jack grounds together and run a single wire to the IG pad of the M³ board.
If the M³ pre-amplifier will also serve as a headphone amplifier, then the ground channel should be fully populated. The headphone jack should be connected as described in the wiring & ground section.
其中be left unpopulated和fully populated是什麼意思啊????
