AM1016 Dual Noise

ARP 1016 Module

Overview This is a replica of the ARP 1016 Dual Noise Source module from the ARP 2500 Analog Modular Synthesizer. The module consists of a two noise sources with pink. white and random outputs. The original design uses the traditional “transistor in avalanche mode” to generate white noise. This signal is then amplified and filtered (using LM301 Op Amps) to create the white and pink noise signals. The white noise is further filtered to produce the low frequency random voltage, using a fourth LM301 Op Amp.

The ARP 1016 module has two identical noise generating circuits, and the noise signals can be selected and turned off using slide switches. These switches also control front panel lights to show the noise has been turned on.

AM4016 PCB (2004)

AM4016 Module I originally replicated the 1016 in the AMSynths 4016 module as a single PCB for each noise source in 2004. At that stage I was building in FracRac format to preserve the 15V rails and because Euro Rack simply had not taken off. The circuits worked fine and were mounted on a PCB panel with a printed paper surface.

I added an Op Amp LED driver circuit to enable a red LED to monitor the slow random voltage level, but this did not prove very useful. The module never made it into a finished cabinet, as although I has designed a complete set of ARP2500 modules as the 4000 series in 2004, they never made it to prototypes. During 2004 I focused on completing my Emu Systems Modular and had no time available for the 2500 project.

AM1016 Module The AM2500 Project was restarted in 2015 and the 1016 laid out in the August on a 150 x 150 mm PCB with wide traces and a planned use of precision PRV6 potentiometers. It is not the most important of modules, so it never made it to a prototype PCB stage.

In 2019 the PCB was refined to use PCB mounted CTS 270X potentiometers which are lower cost and enable the PCB to be mounted directly to the panel. This saves hand wiring and PRV6 pots were at £10 each in 2019, compared with the 270X at £3.

The PCB is laid out for the original TO5-8 can style LM301AH Op Amps, carbon composition resistors, metal can axial capacitors and ceramic disc capacitors (which are used for filtering and bypass). The only changes are modern trimmer potentiometers, 270X potentiometers and LED indicator lights (White, Pink and Red). Standard panel mounted toggle switches are used.

Controls  The module has the following front panel controls:

  • Noise Level A and B
  • Random Level A and B
  • Noise Colour Selection A and B (White, Off, Pink)
  • Random ON/OFF

Connections There are 10x 3.5mm jack sockets mounted at the base of the front panel, these are:

  • Noise A Output
  • Noise B Output
  • Random A Output
  • Random B Output
  • Two 3x Multiples

Build History I bought the ARP detailed service notes back in 2004 and this was the first module I designed and made from the ARP 2500 in the same year. Fast forward 15 years and the 2019 PCB version was ordered in March and built up in October. I ultimately sold the 5U 1016 module.

2024 Update The release of the Behringer 1016 module in Eurorack in 2020 came with a lot of scrutiny from customers, who quickly identified a serious issue with the noise level controls. It turns out the original ARP circuit is flawed. There is a great explanation of the issue and resolution here by Yusynth.

AMSynths released a new set of ARP 2500 Eurorack modules in 2024. One of the additional modules is a reworked 1016 module that contains the corrected 2500 Noise and Random circuits, as well as the 2600 noise circuit with variable colour (pink to white). This module is just 8HP wide and therefore much more space savvy.


Copyright AMSynths 2024