ARP 1004-T Voltage Controlled Oscillator (VCO)

A modular oscillator with dual triangle and sawtooth cores, manual sync via panel switch, and circuitry shared across several ARP modules.

Overview

The ARP 1004-T is a Voltage Controlled Oscillator (VCO) module for modular synthesizer systems. It has triangle and sawtooth waveforms. The square wave derived from the triangle oscillator resets the sawtooth core. Sync is manual, through a front-panel "inhibit" switch. There is no external input to trigger reset. The module is built from two printed circuit boards: the main 1004 VCO board and a dedicated "T" waveform selector board.

Specifications

Product Type	Voltage Controlled Oscillator module
Boards	Main 1004 VCO board and "T" waveform selector board
Waveforms	Triangle and sawtooth
Sync Function	Manual reset via panel switch (no external input)

Design

The 1004-T uses a dual-core design. The square wave output from the triangle core synchronizes the sawtooth wave. The main 1004 VCO board is shared with other ARP modules, including the 1023 Dual Oscillator and the 1045 Voltage Controlled Voice module. It carries transistors (TZ-81, TZ-581, 2N5460), ICs (1339, LM301AH), potted exponential modules (4001-003, 4002-003), and a range of resistors and capacitors with specific values. The "T" waveform selector board carries 2N5460 transistors, 1339 ICs, 2200 pF and 0.01 µF capacitors, and resistors of 390 Ω, 1 kΩ, 10 kΩ, 47 kΩ, and 100 kΩ.

Context

The main 1004 VCO board is also used in the 1004-P, the 1023 Dual Oscillator, and the 1045 Voltage Controlled Voice module. It was a common oscillator platform in ARP's modular synthesizer system.

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