The right-hand side of the front panel governs the combined sum of all inputs:
Switch the QM4 power rocker to the position. The power LED indicator will illuminate. System Settings Quick Reference Use these optimal baselines to dial in your mix safely. Component Parameter Recommended Baseline Operational Function Channel Volumes 12 o'clock (midway) Balances relative levels between performers. Master Volume Start at 0, dial up gradually Sets overall venue sound pressure level. Master Graphic EQ Flat center position (0 dB) Standard room baseline before corrective tweaks. Source Gain Signals Below audible distortion Maximizes headroom without clipping. Operational Best Practices and Gain Staging
| Problem | Possible Cause | Solution | | :--- | :--- | :--- | | | Input not selected. | Check if there is a switch selecting "RCA" vs "XLR" on the back. | | No Sound | Volume too low. | Check both the source volume (phone/PC) AND the amp volume knob. | | Red Clip LED | Overloading. | Turn down the amp volume. If the source device is at 100% volume, it may be distorting the input signal. Lower the source volume and raise the amp volume. | | Protect Mode / Cuts Out | Speaker wire short. | Check rear connections. If positive and negative wires touch, the amp will shut down to protect itself. | | Humming Noise | Ground loop. | Ensure audio cables are not running parallel to power cables. Try a different audio source. | audio choice qm4 manual
: If the mixer was subjected to a sudden power surge or incorrect speaker impedance, the internal fuse may have blown. Disconnect the AC power cord entirely before opening the chassis. Locate the glass fuse on the power supply rail and replace it only with a fuse of the exact same amperage and voltage rating. 2. Audio is Silent but Power Light is On
: For sending the signal to additional amplifiers or recording devices. Footswitch Jack : Allows remote control of the onboard spring reverb. Physical Specifications The right-hand side of the front panel governs
: The built-in reverb and multiple mic inputs make it a popular budget choice for home or bar setups. Public Speaking : Portable enough for seminars and church halls. Where to Find More Info
: Used for low-impedance microphones. Ensure these are connected before powering the unit on. The is a vintage
can be difficult today, but understanding its core schematic, interface layout, and operational parameters allows you to operate this vintage hardware safely and effectively.
: If the audio is too loud or clipping, turn down the Volume on the receiver or the Gain on your mixer.
The is a vintage, highly portable 4-channel, 100-watt powered PA mixer head designed for live performances, rehearsal spaces, karaoke, and small-venue public address applications. Known for its rugged Tolex-covered modular form factor and dependable analog mixing workflow, this manual provides the essential instructions needed to set up, operate, and troubleshoot the hardware safely. Hardware Overview and Control Panel
Use heavy-duty, unshielded 1/4-inch TS speaker cables to bridge the back panel speaker outputs to the back inputs of the passive enclosures.