- Written by John E. Johnson, Jr.
- Published on 11 May 2012
The Design of the Anthem P2 Power Amplifier
The Anthem P2 and P5 are modular power amplifiers, meaning that each amplifer has its own power supply circuitry except for the main transformer, which delivers rail voltage AC to each module.
The amplifier is biased as Class AB, single-ended. However, the XLR input is balanced. This means there is signal inversion on one conductor in the circuit immediately following the XLR input jack. The two signals, one inverted with respect to the other, are combined before being sent to the input stage, which is single-ended as is the remaining portions of the amplifier, e.g., the output stage. This provides for Common Mode Rejection (CMR) of any noise that is picked up along the way coming in from the cable feeding the XLR input.
The single-ended nature of the amplifier allows it to drive very low impedance loads, which is the principal reason I chose the P2 to try out with my ESLs (besides the fact that the P series is highly regarded). Each module has 14 output devices, which is another reason it can work with low-impedance loads.
The rear panel of the P2 is easy to deal with because the chassis is the same one as in the P5. So, the two sets of speaker binding posts are spread out nicely for big fingers like mine, and the switches for changing the input from XLR to RCA also have plenty of room. The AC recepticle is a two-prong non-grounded type. Even though there are only two modules in the chassis, it still weighs a hefty 75 pounds, and the two handles on the rear are useful for moving the amplifier.