ARP 4019

Voltage Controlled Amplifier module for the ARP 2600 synthesizer

Overview

The ARP 4019 is a Voltage Controlled Amplifier (VCA) module for the ARP 2600 synthesizer. It replaced the earlier ARP 4010, which was used only in the first 2600 units. Dennis Collins designed it, and it has both linear and exponential control voltage inputs. The 2600 needs trimmer adjustments to keep the module from distorting, though the CV rejection and high-frequency rejection trims have little effect. There is also a known circuit board error in the ARP 2600. It places the exponential trim across V+ and GND instead of between -V and V+, which is how the original Tonus 4019 schematic has it.

Design

The ARP 4019 VCA is a long-tailed pair with a current mirror and a diode buffer, built around a non-potted 4005 VCA type 1P. It uses three pairs of matched transistors to minimize VCA thump, a characteristic of the original ARP design. The exponential converter uses complementary transistors Q1 and Q2 with matched saturation currents (Is) and base-emitter voltages (Vbe). An external 54.9K resistor on pin 4 drives it. The linear control voltage drives a 100K external resistor on pin 3. A Wilson current mirror (Q6, Q7, Q8) sums the currents from the two inputs and sets the operating current for the differential pair (Q9, Q10). That pair's collector load is a cascode current mirror (CR10, Q11, Q12, Q13). Audio goes to both sides of the differential pair, and an LM301 opamp works as a current-to-voltage buffer to turn the output current into voltage.

Specifications

Format	Original ARP 2600 sub-module
Linear CV Input	Drives 100K external resistor connected to pin 3
Exponential CV Input	Drives 54.9K external resistor connected to pin 4
PCB Mounting	Long gold PCB pins not supplied; 1mm gauge wire can be used

Context

The ARP 4019 VCA module was used only in the ARP 2600 synthesizer and is not a standalone instrument. It succeeded the ARP 4010, which appeared only in early ARP 2600 units. Modern reproductions, such as the New England Analog NEA-4019, come as Eurorack modules and PCB/panel sets for repair or DIY replacement.

Market

A New England Analog NEA-4019 clone PCB/panel set sells for $40.00.

Similar items on eBay

No exact ARP 4019 listings are live right now — these searches show current ARP and similar vintage synth gear on eBay:

Search ARP 4019 on eBay Browse ARP synth gear on eBay

As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.