What type of EQ circuit maintains a constant Bandwidth (Q) despite amplitude adjustments?

The correct choice is Constant-Q because this type of equalization circuit is designed so that its bandwidth, or Q factor, remains unchanged regardless of the amplitude adjustments made to the gain. This characteristic is particularly useful in audio production and live sound, as it allows for precise control over frequency adjustments without altering the overall bandwidth of the affected frequencies.

In contrast, other types of EQ circuits, such as variable-Q or parametric, can have their bandwidth altered when the gain is adjusted. Variable-Q circuits allow for a change in the Q factor based on the amplitude, leading to broader or narrower bandwidths depending on how much boost or cut is applied. While parametric EQs can offer a range of features, they still generally include the capability to change Q in relation to gain adjustments, which differentiates them from constant-Q designs. Graphic EQs, while useful for visual representation of frequency adjustments, also do not maintain a constant Q; instead, they have fixed bandwidths for each band that can be adjusted independently. Therefore, constant-Q EQs provide the stability in bandwidth that is essential for certain audio applications.