Wire a Balanced Microphone to Unbalanced Inputs
How to connect a Professional XLR Mic to a Consumer 3.5mm Jack
Aug 11, 2008
Camcorder users can boost sound quality greatly by getting the mic off camera and closer to the actors. However, professional microphones tend to come with balanced XLR connections whereas much consumer and semi-pro gear comes with 3.5mm jack inputs. See the pictures with this article for what these connectors look like.
Connector Pinout
The first thing to identify is what signals are present. On a balanced 3-pin XLR cable, the connections are as follows:
Pin 1 – cable shield
Pin 2 – signal +
Pin 3 – signal –
The connector carries a mono signal from the single microphone. It is common practice to connect this mono signal to both left and right channels of a stereo input.
On a typical unbalanced 3.5mm consumer jack socket as a mic input, the jack connection is
Tip – Left hand +
Ring – Right hand +
Sleeve – left and right ground
Microphone Powering
Check how the microphone is powered. Professional and stage microphones can be unpowered, battery powered or phantom powered. Most vocal stage microphones are dynamic mics and these do not need power. Some capacitor (a.k.a. condenser) and electret microphones take a small battery, and these also do not need external power.
Other professional capacitor microphones need 48V supplied along the microphone cable, called P48 phantom power. These can be connected to unbalanced inputs. How to do that is described in Use Phantom Power Mics with Consumer Camcorders.
Dynamic microphones.
These are low output compared to capacitor/electrets. A step-up microphone transformer is a good option to connect a dynamic mic to a typical unbalanced consumer microphone input. The transformer raises the signal level a little, which reduces noise a bit, and keeps the microphone cable balanced. The transformer should be located close to the recorder end, not the microphone end. Alternatively dynamic microphones can be connected like battery-powered capacitor microphones.
Dynamic and Battery-powered Capacitor Microphones
An adapter cable can be used - connect the pins like so
XLR pin 1 (ground) to the minijack sleeve
XLR pin 3 (signal -) to the minijack sleeve. Pins 1 and 3 can be shorted at the socket to save extra wiring)
XLR pin 2 (signal +) to the minijack tip and ring. This puts the mono microphone signal onto both stereo channels of the consumer recorder.
Stereo working
If two mono microphones are to be used for stereo then it is possible to vary the wiring, by taking XLR pin 2 of the left-hand mic to the minijack tip and XLR pin 2 of the right-hand mic to the ring. Pins 1 and 3 of both XLRs are taken to the sleeve, as before.
These adapter cables are available from some specialized audio suppliers, but are not as well known as they should be to consumer electronics suppliers.
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