How To | Understand the difference between bridging and paralleling on QSC Cinema DPA Amplifiers

Learn about the differences between bridging and paralleling QSC Cinema DPA Amplifiers for optimal operation.

Updated at June 8th, 2023


QSC’s DPA and DPAQ amps have feature called Flexible Amplifier Summing Technology (FAST). This gives the user the option of bridging 2 channels together or paralleling 2 (or more) together to increase the power output when necessary.

Bridging two channels together (A+B) effectively doubles the output voltage that the load sees. Paralleling two channels together will double the available current.

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Since the DC voltage rails of the DPA 4.3 and 4.5 are already very high (higher than the DCA3422), there is little benefit to operating them in bridge mode.


See the figure below for the behavior on the DPA4.5 amplifier at Power Output(Y axis) vs Load Impedance(X axis). Notice the available voltage is doubled by bridging two channels (A+B), show in the yellow area. In this region, more power is available at higher impedances, but there is not much benefit in the power transfer at the lower impedance range (2-5Ω).

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In cinema, most applications that require increased power output also tend to be scenarios with low impedance loads. The Pink (AB) region in the figure above.


  • LF cabinets for stage speakers (4-6ohm)
  • Subwoofers (4ohm)
  • SR-1590 surrounds in Atmos rooms
  • Surrounds wired in parallel (2-4ohm)

For this reason it’s typically best practice to operate the DPA(Q) 4.3, 4.5, 8.4, and 8.8 amplifiers in parallel(AB) not bridge mode(A+B). The DPA(Q) 4.2 is the one exception where it may benefit to run in either bridge mode depending on the application.