Digital Sound & Music: Concepts, Applications, & Science, Chapter 1, last updated 6/25/2013
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The ¼" phone plug and its corresponding jack (Figure 1.28) are also widely used. The
¼" plug comes in two basic configurations. The first is a Tip/Sleeve (TS) configuration. This
would be used for unbalanced signals with the tip carrying the audio signal and the sleeve
connecting to the shield of the cable. The TS version is used on musical instruments such as
electric guitars that have electronic signal pick-ups. This is an unbalanced high-impedance
signal. Consequently, you should not try to run this kind of signal on a cable that is longer than
fifteen feet or you risk picking up lots of noise along the way and get a significant reduction in
signal amplitude. The second configuration is Tip/Ring/Sleeve (TRS). This allows the connector
to work with balanced audio signals using two-conductor cables. In that situation, the tip carries
the positive polarity version of the signal, the ring carries the negative polarity version, and the
sleeve connects to the signal ground via the cable shield. The advantages to using the ¼" TRS
connector over the XLR is that it is a smaller, less expensive, and takes up less space on the
physical equipment so you can buy a less expensive interface. However, the trade-off here is
that you lose the locking ability that you get with the XLR connector, making this connection
more susceptible to accidental disconnection. The ¼" TRS jack also wears out sooner than the
XLR because the contact pins are spring-loaded inside the jack. There's also the possibility for a
bit more noise to enter into the signal because, unlike the XLR connector, the ¼" TRS connector
doesn't keep the signal pins perfectly parallel throughout the entire connection. Thus it's possible
that an interference signal could be introduced at the connection point that would not be equally
distributed across both signal lines.
1/4" Tip/Sleeve plug
1/4" Tip/Sleeve jack
1/4" Tip/Ring/Sleeve
plug
1/4" Tip/Ring/Sleeve
jack
Figure 1.28 TS and TRS connectors
The Neutrik connector company makes a XLR and ¼" jack hybrid panel connector that
accepts a male XLR connector or a ¼" TRS plug, as shown in Figure 1.29. Depending on the
equipment, the XLR connector could feed into a microphone preamplifier and the ¼" jack would
be configured to accept a high-impedance instrument signal. Other equipment may just feed both
connector types into the same signal line, allowing flexibility in the connector type you use.
Figure 1.29 Neutrix XLR and 1/4" combination connector
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