Ampeg B15N Bass Amplifier

The B-15N centers on two versions of the Ampeg circuit rather than a generic bass-amplifier tone stack. Its 1964 and 1966 channels have distinct bass and treble responses, and the power-amplifier bias can be selected independently of the preamp. This makes it possible to compare complete period configurations or deliberately mix their characteristics.

Behind the amplifier is a studio-oriented FX Rack. Recording Chains combine cabinet and recording-path coloration, while Tight and Smooth filters can work before the amp or on its processed output. Input Gain determines how hard the preamp is driven; Power Soak controls the level of a driven power stage without making the same tonal change as backing down the amplifier.

For a practical starting point, choose a channel, keep input gain conservative, and audition recording chains before fine-tuning the tone controls. With compatible Apollo hardware, the Unison insert adds input-stage integration. Recording a dry DI while monitoring processing leaves the amp and cabinet choices open for the mix.

Manual, The Basics, p. 3; The Controls of the Ampeg Amplifier Section, p. 4; The Controls of the Ampeg FX Rack, pp. 5–7.

Amplifier

• Input Channels selects the 1964 B-15NC or 1966 B-15NF circuit. The upper jacks are unattenuated; the lower jacks apply a −15 dB input pad for hotter sources.
• Volume adjusts the selected channel's level. Use it as part of the amplifier sound, rather than substituting it for final output compensation.
• 1964 Treble / Bass provide ±18 dB at 5 kHz and ±10 dB at 40 Hz respectively. Both are flat at their center positions.
• 1966 Treble / Bass have different responses: Treble offers +18/−30 dB at 5 kHz; Bass offers ±11 dB at 40 Hz. Compare channels at similar perceived loudness rather than identical knob positions.
• Bias switches between 1964 cathode bias and 1966 fixed bias independently of channel selection. Power engages or bypasses processing.

FX Rack

• Noise Gate On, Threshold, and Range control whether gating operates, the input level that closes it, and the amount of attenuation. The Closed indicator shows when reduction is active. Raise the threshold only enough to suppress pauses without clipping note endings.
• Tight removes lows and Smooth removes highs. Each can be placed Pre, Post, or Off. Pre filtering changes what excites amplifier distortion; post filtering reshapes the completed amp tone.
• Input Gain compensates for pickup or recorded-DI level and adjusts preamp drive. Power Soak reduces the level of the modeled power-amp output while retaining its driven character.
• Rec Chains selects a combined cabinet/recording setup; the plus/minus controls step through choices. Auto / Bar auditions chains every one, two, or four host-tempo bars. Stop Auto when a useful chain appears.
• Horn adds the separately captured horn contribution. Empty Play Real Cab omits the internal cabinet chain when using another cabinet solution.

Comparisons

A/B/C/D stores four variations within a preset. Copy / Paste duplicates a starting sound, and Undo / Redo makes comparisons reversible. Use these to compare bias and cabinet choices with otherwise matched settings.

Manual, Amplifier Section, p. 4; FX Rack, pp. 5–7; Settings / Top Toolbar, p. 8.