How do you setup for amplifier measurement?

Measurement setup is critical for nearly all applications, and for amplifiers this is no different. Audio analyzers are highly effective tools for audio power amplifier measurements, as they can handle the wide voltage and frequency ranges commonly seen in audio amplifier testing. 

For most amplifier tests, non-inductive dummy loads are essential. These loads must be appropriately sized and well heatsinked to handle the amplifier’s full output power, and dummy loads ranging from wire-wound resistors to precision thin-film metal-film resistors can be used depending on the amplifier under test. Testing filterless Class D amplifiers is unique, as their design depends on the inductance of connected speakers for low-pass filtering; using purely resistive loads may lead to inaccurate results. In these cases, inserting an Audio Precision AUX filter in series with the analyzer inputs can prevent carrier signal overloads and false readings. 

The overall measurement configuration is quite simple: connect the analyzer outputs to the amplifier inputs and the amplifier outputs to the analyzer inputs, along with the dummy loads. With Class D amplifiers, which often have DC bias, it’s necessary to use balanced inputs and properly sized speaker wires to avoid significant voltage drops. Paying attention to grounding configuration minimizes noise pickup, and lifting the shield on one end can help with balanced connections. For reference levels, set 1-watt output as the generator reference level, and configure impedance as needed. Finally, filters are generally set at 20 kHz, which is particularly important for Class D amplifier accuracy, while DC level verification ensures proper operation in DC-coupled amplifiers.