Tutorials and Guides

Investigating Signal Chain Optimization

by João Neves
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Anyone working with amplified and electronic instruments has experienced signal chain issues of one kind or another. With the output of one device routed into another, characteristics of the chain can develop causing a well-known villain in the audio world to appear- noise. In its various manifestations noise can be annoying and difficult to deal with. However things are not always as they appear on first listen and a closer look at a few common factors can clarify the true nature of the unwelcome tones… 

In this entry I will bring to mind some common circumstances and possible solutions within the MOD system. Starting with some of the quintessential system settings that intersect with this issue.

The first factor to consider is Gain Staging. Managing the relative levels in each step of an audio signal flow in the process, falls into this concept. This includes faders in a DAW, or mixing consol as well as inserts. If you happen to find the input signal is a bit too quiet, we suggest to increase the gain on the device connected to the input, while decreasing on the MOD Device output using a Gain plugin or Master Volume when appropriate. If the output signal is too quiet, increase the output on the MOD Device while decrease gain in device connected to output when appropriate. Taking a moment to assess where the volume adjustments need to be made are always crucial step in music making so dont over look the obvious. 

  1. Gain staging
    1. input signal too quiet
      • increase gain on device connected to input, decrease on MOD device
    2. output signal too quiet
      • increase output gain on MOD device / decrease gain in device connected to output

Secondly the pedalboard arrangement should be monitored for any possible signal modifications that the effects themselves might make or when aligned in a series. Some amp and tape simulators color the signal with their own programammed enhancements and often can be dialed back when necessary. When this is not the case and when dealing with compressors or amplifiers we suggest using a Noise Gate to filter out all sounds happening below a dialed in DB. This is common practice and can be carried out in a straightforward way or creatively depending on the settings. Again exploring the unique characteristics of each plug in is very important to get the ideal sound. 

  1. Pedalboard
    1. compresses / amplifies pick-up noise
      • use noise gate
    2. plug-in generating noise (as the original)

The third more hardware centered zone to consider is when Ground Loop is in effect. This is a much wider topic and falls into a few possible physical arrangements within your instrument and effects system. This encompasses the holistic connection environment including the power source and cables used. Here are a few examples of connection points and solutions. 

Some places to investigate within the ground loop occurrence. 

  1. Ground loop (modulated 50/60Hz hum)
    1. multiple grounded devices plugged to different power sockets
      • use same power strip (limit loop size)
      • keep power cables closely together (limit loop size)
      • check for other equipment leading to interferences (e.g. dimmed LED)
      • experiment with other power sockets (increases loop size, but could be less prone to interference due to shape and orientation)
    2. unbalanced cables between MOD device and grounded gear (e.g. mixer)
      • if the receiving device has one, try using the “ground lift” switch.
      • add passive DI / ground loop isolator if receiving device has unbalanced ports
      • use balanced cables if receiving device has balanced ports
      • experiment with passive DI / ground loop isolator if noise persists with balanced cables (insufficient common mode rejection)
    3. USB connection to grounded device (e.g. computer)
      • use MOD USB cable
      • try without USB connected
      • try different USB port
      • try through a USB hub
      • add USB isolator 

The complex nature of signal routing and audio processing can be observed as a directional web of connection moving in a defined direction but being affected by other internal webs. Having a good understanding of the overall hardware architecture and cabling profile will open up whats happening within the signal chain. Overall this guide is quite specific to the MOD hardware system but can be applied to most effects led environments you might encounter. Happy patching!