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#### Power amplifier modes : stereo, parallel and bridge mono

In general, two-channel power amplifiers for professional use default to stereo mode. That is, each amplifier channel receives a signal from its input connector and its volume is controlled by... Read more

#### Basic electricity formulas

Although it not specific to sound, we include this document with some basic electricity formulas. They can be found in any electricity textbook, but we have added them to the DoPA Library for reference.

## Ohm's law

The most basic formulas derive from Ohm's law, which specifies that the electric current between two points is proportional to the potential difference (voltage) between them and inversely proportional to the resistance between them. The formula is:
 V I = ——— Z

where I is the current (intensity) in amps and V is the voltage in volts. Since we use alternating current in audio, we have replaced resistance with impedance (Z, and this could also be resistance R), measured in ohms. Clearing Z and V we have these other two formulas:

 V Z = ———