A Musician's Intro to Live Sound, Pt. 2 - Inputs

Our previous blog post gave us a framework for talking about live sound: the three sections of the live sound system (inputs, transmission, outputs). We also introduced some of the different signal types (mic vs. line level, balanced vs. unbalanced). The one thing that will help the most in understanding a live sound system is knowing the differences between these signal types, and knowing which type of signal each piece of equipment uses. This blog post digs in deeper to the key fundamentals that a musician needs to know about the first part of the live sound setup: inputs.

Almost all input equipment takes physical vibrations and turns it into electrical signals. For a microphone, this is the physical vibration of the air (sound). For pickups, like on your guitar, this can be the physical vibration of the body of the instrument (such as on the bridge of a violin) or the vibration of metal in a magnetic field (the strings of your electric guitar). A few instruments (keyboards, synths, etc.) just produce electrical signals directly.

Let’s go through each one and point out what you need to know.

Microphones

A standard SM57 microphone. Notice
the round top, which is the pop filter.

In almost all live sound settings, you’ll be using dynamic microphones. This especially true in small, loud clubs (or where every musician that isn’t famous plays). The vibration of the air produces the electrical signal directly, so they don’t need external power. The Shure SM58 and SM57 are the most common ones you’ll see. These are very similar mics, but the SM58 has a built-in pop filter, so it’s used for vocals while the SM57 is used for instruments.

A condenser microphone is more sensitive, more delicate, and typically needs phantom power. Some instruments using small clip-on microphones are condenser (violin, saxophone), and in a setting where you can control the sound (recording studio) you can get better sound quality.

What you need to know:

• The biggest thing a musician needs to pay attention to is the position of their microphone. Just because it’s kinda near you doesn’t mean it will pick up sound. Keep it pointed directly at your mouth or instrument at all times. Take one minute to watch this video and you’ll understand what I mean:
  
  

• If you’re using a condenser microphone and aren’t getting any sound, it’s probably because the microphone needs phantom power.
• Microphones produce mic level signals (surprise!).

Instruments

Besides how to play your instrument, the main thing you need to know is whether you’ll use a cable or a microphone to connect to the system, and, if you’re using a cable, what type of signal your instrument produces.

• Guitar and bass pickups create an instrument level out. 
• A guitar or bass amplifier will often have a line out, or you can put a microphone in front of the speaker that is integrated into the amp.
• Keyboards typically have line out.
• Other instruments will use a microphone.

Almost all the rest of the stuff on your stage is designed to move electrical signals from place to place, or to change signals from one type to another. We'll get into that in more detail with our next blog post in the series, which is all about transmission.

Next post: Transmission