5 Power amplifiers
5.3 Minimum load
There's only so much an amplifier can drive. It is designed for a specific minimum load impedance. This is not the actual output impedance of the amp itself 
, but a rating for the load that can be safely connected to the amplifier. This has to do with the maximum output current the amplifier can deliver, as a low-impedance load draws more current than a higher-impedance load. It may be hard to understand why it's called minimum load, but as described earlier , amplifier load increases when impedance decreases.
Now for some real world examples:
- If an amplifier is capable of driving an 8 Ω load, it can drive 1 8 Ω cab. With a special series-Y cable it can drive two identical 4 Ω or 8 Ω cabs.
- If an amplifier is capable of driving a 4 Ω load, it can drive 1 4 Ω cab or 2 8 Ω cabs.
- If an amplifier is capable of driving a 2 Ω load, it can drive 2 4 Ω cabs, 1-4 8 Ω cabs, or 1 4 Ω cab AND 1 or 2 8 Ω cab(s).
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© Joris van den Heuvel 2001-2009