LOW-CUT Filter Action, Controls and Connectors

CONTROLS AND CONNECTORS

WARNING

This apparatus must be earthed (grounded)! The M267 power supply is energized when the unit is connected to an ac source; disconnect mains (power) plug from supply when not in use.

Inputs

The four inputs are professional three-pin female XLR audio connectors located on the rear panel and designated INPUT 1 through INPUT 4. The inputs are balanced (inter- nal transformer, MUMETAL shielded); pins 2 and 3 are ªhotº, and pin 1 is ªgroundº. For microphone operation, the switches labeled LINE/MIC (directly above the input con- nectors) must be in the MIC position; for line level inputs, the switches must be in the LINE position. For impedance, clipping and operating signal levels, refer to the SPECIFI- CATIONS section.

Outputs

The rear-panel connector labeled OUTPUT is a profes- sional three-pin male XLR audio connector. With the adja- cent LINE/MIC switch in the MIC position, the OUTPUT connector is used to feed a low-impedance microphone line or a low-impedance microphone input. With the LINE/ MIC switch in the LINE position, the OUTPUT connector feeds the line-level input of an amplifier, tape recorder, or another mixer. The OUTPUT connector is a balanced out- put with the LINE/MIC switch in either position; pin 1 is ground, pins 2 and 3 are ªhotº, and the connector is in phase with the corresponding pins of the input connectors.

The rear-panel binding-post connector designated LINE OUTPUT is in parallel with the OUTPUT connector and can be used as a line-level output feed simultaneously with the OUTPUT connector. The terminals are numbered 2 and 3 and are in phase with the corresponding pins of the input connectors. While the line outputs can be used to drive various impedance lines, the VU meter is calibrated for use with a 600 Ω line.

The line output transformer will operate properly with up to 100 mA dc in the line. This feature permits the use of standard ªdialed-upº telephone lines with dc across them. (Since a slight distortion increase may occur at high output levels with maximum dc current, operation with the VU RANGE switch at +4 dBm is recommended.)

Input Gain Controls

The front-panel controls designated 1 through 4 are the in- dividual active gain controls for correspondingly numbered inputs. Note that the input connectors are located on the rear panel directly behind their corresponding gain control. The controls set the preamplifier gain and provide preamplifier output attenuation. As the gain is reduced, the preamplifier input clipping level is increased for that channel.

Input control 1 serves an additional function as the level control for the tone oscillator when the INPUT 1/OCS 1 switch is in the OSC 1 position.

IMPORTANT: For optimum signal-to-noise ratio, the indi- vidual input controls should be operated at as high a set- ting as possible, consistent with maintaining adequate control range and input clipping level.

Master Gain Control

The front-panel control designated MASTER is the mas- ter gain control which sets the overall output level of the mixed sources (including signals applied to the MIX BUS input).

Limiter

The front-panel LIMITER IN/OUT switch turns on a fast- acting, peak-responding limiter circuit that cuts overload distortion during loud program intervals without affecting normal program levels. When the LIMITER switch is IN (operating), the mixer output is limited to approximately +15dBm. Increasing the individual or MASTER gain con- trols will increase the average output and the amount of limiting. The limiter threshold can be reset to any other out- put between ±4 and +18 dBm if desired. With the limiter switched OUT and tone oscillator activated, adjust INPUT 1 and MASTER level controls to produce an output 0.5 dB higher than desired. Switch the limiter IN and set the LIM- ITER THRESHOLD ADJUST control (accessible though the bottom of the chassis) for the desired level.

The front-panel PEAK LED indicator shows limiter op- eration with the limiter in, and operates when program lev- els approach overload with the limiter out. The indicator is much faster than a meter and will be activated by the short- est transient peak, but it remains on long enough to provide easy recognition.

Low-Cut Filters

The low-cut filters provide a low-frequency rolloff to the response curve as shown in Figure 2. The filters are acti- vated by the LO-CUT IN/OUT switch above each individual input gain control and can be used individually with each control to reduce wind noise or undesirable low-frequency signals such as from condenser microphones or turntable rumble.

0
±10
±20
20	50	100	200	500	1,000

LOW-CUT FILTER ACTION

FIGURE 2

M267 specifications

The Shure M267 is a versatile and robust audio mixer designed primarily for professional audio environments. Known for its high-quality sound and reliable performance, this mixer has been a staple in both live and studio applications. One of the standout features of the M267 is its four-channel configuration, which allows for multiple audio sources to be mixed simultaneously. This makes the mixer ideal for a variety of settings, including live events, broadcast, and recording sessions.

The M267 employs a range of advanced technologies to ensure optimal sound quality and user experience. One of the key technologies within the M267 is its low-noise preamps, which are designed to deliver clear and precise audio with minimal background noise. This is particularly important in professional environments where clarity is paramount. The mixer also includes a built-in limiter, which provides additional control over audio dynamics, preventing distortion during loud peaks and ensuring a clean signal.

The M267 features a simple and intuitive user interface that makes it easy for users of all skill levels to operate. Each channel is equipped with individual level controls, EQ settings, and PFL (Pre-Fader Listen) capabilities. With these controls, operators can tailor the audio signal to their specific requirements, whether they are balancing microphones, musical instruments, or playback devices.

Another significant characteristic of the M267 is its rugged construction. Designed to withstand the rigors of frequent transport and use in demanding environments, the mixer is built with high-quality components that ensure durability and longevity. Its compact size also makes it an excellent choice for mobile setups, allowing audio professionals to transport it easily from one location to another.

Furthermore, the Shure M267 incorporates flexibility in its connectivity options. It provides various input and output configurations, allowing seamless integration with other audio equipment. This versatility makes it a suitable choice for both permanent installations and portable setups.

In summary, the Shure M267 is a highly regarded mixer that combines professional-grade sound quality with practical features tailored for audio professionals. Its low-noise preamps, intuitive controls, rugged build, and flexible connectivity position it as an excellent choice for anyone seeking a dependable and effective audio mixing solution in both live and recorded scenarios. Whether in the studio or on stage, the M267 consistently delivers the performance that audio professionals demand.