Microphone, Line & Instrument Inputs

Microphone preamplifiers

ASP880 has eight Class-A microphone preamplifiers with a discrete eight-transistor front end. The preamp provides 0–60 dB gain and an equivalent input noise of less than −127.5 dBu.

Channels 1 and 2 include a −10 dB pad, extending their padded gain range from −10 to +50 dB for hot sources such as kick and snare drums.

Line inputs

The 1/4-inch TRS socket in each rear-panel Combi connector is a padded balanced line input with an input impedance greater than 6 kΩ. The line signal passes through the microphone preamp and can use polarity reverse, variable input impedance and the high-pass filter, but not phantom power.

The input-impedance switch also acts as a variable pad for line-level signals.

Discrete JFET instrument inputs

Channels 1 and 2 provide front-panel Class-A JFET D.I. inputs. Inserting a 1/4-inch TS plug automatically selects the instrument signal in place of the corresponding rear-panel input.

The 1 MΩ input impedance is intended to reproduce the loading of a classic guitar amplifier input. Passive guitar and bass pickups may have source impedances from approximately 6 kΩ to 40 kΩ, depending on volume and tone control positions. A high input impedance avoids loading the pickup excessively and helps retain its signal and tone.

JFETs are valued for tube-like behaviour when overdriven. When pushed, the ASP880 D.I. circuit can add second- and third-harmonic distortion, from a specified minimum THD+N of less than 0.03% at 0 dBu to much stronger colouration at higher drive.