ARP Little Brother (1975 - 1977)

Name: ARP Little Brother
Brand: ARP

Keyboardless monophonic expander module designed to add an extra VCO and LFO to ARP synthesizers.

Overview

The ARP Little Brother is a keyboardless monophonic expander module. ARP Instruments, Inc. made it from 1975 to 1977. It was an add-on for other ARP synthesizers, commonly sold with the ARP Axxe. During a summer 1976 promotion, it was given away free with the purchase of an ARP Odyssey. The idea was to "fatten up" the sound of synths like the Axxe, Odyssey, 2500, and 2600 by adding an extra VCO and LFO. You can stack multiple Little Brothers for expanded, modular-like functionality.

Specifications

Production Years	1975 - 1977
Synthesis Type	Analog Subtractive
Oscillator	1 VCO with four selectable and stackable waveforms: brass (sawtooth), hollow (square), reed (pulse), and fuzz (pulse with PW modulation); includes sub-octave divider for -1, -2, and -3 octaves
LFO	1 LFO with triangle waveform; LFO out available
External Control	CV/Gate, ARP System Interface
Additional I/O	CV, Gate, and Trigger inputs; LFO out
Controls	Pitch bend/master tuning knob (2-octave range), LFO speed and vibrato depth sliders
Missing Components	No VCF, no VCA, no envelope generator (ADSR)
Memory	None
Effects	None
Arpeggiator/Sequencer	None

Design

Inside is a genuine ARP 4027 oscillator submodule, and the unit uses ARP's System Interface to talk to other synths. You connect its CV input to an ARP keyboard and route its audio output into the external audio input of a companion synth. The "big brother" synth then processes the signal through its VCF and VCA. The unit uses organ-style tone generation to get multiple notes from one oscillator. Components include a 1N4148 diode, 1458 op amp, 3086 transistor array, 4024 binary counter, 2N3904 transistor, and various potentiometers. A small hole above the Reed switch gives access to a calibration trimmer.

Context

The Little Brother was designed to augment the Axxe or Odyssey. It could be used with any analog synth that has a 1V/octave CV output and an external audio input. It was marketed as a way to add an extra oscillator and LFO to existing ARP systems, and you could stack multiple units for richer sound expansion.

Market

A refurbished unit is currently listed for $1,400 in good condition, with scratches but fully functional. The refurbishment included new sliders, a recapped power supply, replacement of all tantalum capacitors (except on 4027), replacement of all CMOS and op amp ICs, a new pitch bend knob, and calibration. Cosmetic flaws include a missing front tag, replaced switches, a missing switch cap, a power lamp that doesn't light, and panel scratches. Replacement parts are available: 1N4148 diode ($0.95), 1458 op amp ($2.95), 3086 transistor array ($9.95), 4024 binary counter ($2.95), pitch bend knob ($7.95), and slide potentiometers ($29.95 each).