An apparatus for coupling RF and AC signals to provide power to a multipole in a mass spectrometer, the apparatus comprising: a first circuit (210, 410) comprising: an RF power source (230, V1) configured to provide difference mode power to said multipole via said RF signal; at least one inductor (232, 234, L3, L4) configured to form at least one resonant LC circuit with said multipole to provide voltage gain for said RF signal; and a transformer (250, TX4) comprising a secondary tap, said transformer connected in parallel to said RF power source and further connected to said at least one inductor such that signals injected into said secondary tap are communicated to said at least one resonant LC circuit; and a second circuit (220, 420) comprising: an AC power source (260, V2) configured to provide common mode power to said multipole via said AC signal, an output from said second circuit connected to said secondary tap such that said common mode power is injected into said first circuit and said multipole can be operated in common mode and difference mode simultaneously; and a further at least one inductor (264, L5) configured to form a further resonant LC circuit with said multipole via said transformer to provide voltage gain for said AC signal, wherein each of said RF power source and said AC power source is configured to operate at the same frequency and with a predefined phase difference, such that the addition of each said RF signal and said AC signal results in an RF unbalance on said multipole, that is controllable by varying said phase and amplitude of said AC signal. a first circuit (210, 410) comprising: an RF power source (230, V1) configured to provide difference mode power to said multipole via said RF signal; at least one inductor (232, 234, L3, L4) configured to form at least one resonant LC circuit with said multipole to provide voltage gain for said RF signal; and a transformer (250, TX4) comprising a secondary tap, said transformer connected in parallel to said RF power source and further connected to said at least one inductor such that signals injected into said secondary tap are communicated to said at least one resonant LC circuit; and an RF power source (230, V1) configured to provide difference mode power to said multipole via said RF signal; at least one inductor (232, 234, L3, L4) configured to form at least one resonant LC circuit with said multipole to provide voltage gain for said RF signal; and a transformer (250, TX4) comprising a secondary tap, said transformer connected in parallel to said RF power source and further connected to said at least one inductor such that signals injected into said secondary tap are communicated to said at least one resonant LC circuit; and a second circuit (220, 420) comprising: an AC power source (260, V2) configured to provide common mode power to said multipole via said AC signal, an output from said second circuit connected to said secondary tap such that said common mode power is injected into said first circuit and said multipole can be operated in common mode and difference mode simultaneously; and a further at least one inductor (264, L5) configured to form a further resonant LC circuit with said multipole via said transformer to provide voltage gain for said AC signal, an AC power source (260, V2) configured to provide common mode power to said multipole via said AC signal, an output from said second circuit connected to said secondary tap such that said common mode power is injected into said first circuit and said multipole can be operated in common mode and difference mode simultaneously; and a further at least one inductor (264, L5) configured to form a further resonant LC circuit with said multipole via said transformer to provide voltage gain for said AC signal, wherein each of said RF power source and said AC power source is configured to operate at the same frequency and with a predefined phase difference, such that the addition of each said RF signal and said AC signal results in an RF unbalance on said multipole, that is controllable by varying said phase and amplitude of said AC signal.