INST – two switches changing the input configuration for the jack contacts at Inputs 1 and
2. When INST is selected, the gain range and input impedance are altered (relative to LINE),
and the input is made unbalanced. This optimises it for the direct connection of instruments
(usually via a 2-pole (TS) jack plug). When INST is off, the inputs are suitable for the connection
of line level signals. Line level signals may be connected either in balanced form via a 3-pole
(TRS) jack or unbalanced via a 2-pole (TS) jack. The switches each have an associated red LED
indicating that INST is selected.
你用前面那两个孔 它有切换开关 INST那个 按下去就是乐器输入 不按就是线路输入,你的话放接这个孔不会二次放大的应该