RDL RU-MX4 4 Ch Mic/Line Mixer with Phantom Power & Mic/Line Output

MSRP: $568.94
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The RU-MX4 is the ideal choice in many applications where a combination of balanced mic and/or unbalanced line-level signals needs to be mixed. Balanced connections use XLR connectors. Unbalanced signals are coupled through phono jacks. Each of the four inputs can accept either a balanced XLR mic or an unbalanced line-level input. 24 V phantom is individually switch selectable for each mic input. The unbalanced phono jack LINE OUTPUT from one RU-MX4 may connect to the unbalanced input of other equipment, or may be connected to the DIRECT input of another RU-MX4 to expand mixing capabilities. The RU-MX4 provides one balanced output, switchable for mic or line level. Audio levels are adjustable on the front panel. Each input channel is equipped with a front-panel dual-LED VU meter that follows standard VU ballistics. The final mix is displayed on an LED string VU meter featuring a visually comfortable arc motion. A rear-panel switch allows the soft-knee compressor to be switched in or out. A factory installed output isolation transformer is available by ordering the RU-MX4T.


  • Four Channel Audio Mixer with Expansion Capability
  • XLR Microphone Inputs, Phono Jack Line Inputs
  • Switchable 24 V Phantom for Each Mic Input
  • Mic or Line XLR Output, Switchable
  • Unbalanced Line Output and Direct Input
  • Integral Compressor/Limiter, Switchable
  • Studio-Quality, Low-Noise Performance



Microphone Inputs (4):
2 kΩ balanced, switchable 24 V phantom (IEC 61938: 2013)

Mic Input Level for +4 dBu output:
-58 to −20 dBu (PHANTOM OFF or ONHI gain); -41 to −4 dBu (PHANTOM ON LO gain)

Line Inputs (4):
2 kΩ unbalanced

Line Input Level for +4 dBu out:
-25 dBV to +20 dBV, -10 dBV nominal

Gain Adjustments (5):
Mic: Off to 62 dB gain (PHANTOM OFF ONHI gain);
Off to 46 dB gain (PHANTOM ON LO gain);
Line: Off to 27 dB gain

Output Attenuator:
0 dB to infinity

Frequency Response:
Mic: 80 Hz to 30 kHz (± 1.5 dB),
<-10 dB @ 20 Hz (integral high-pass filter)
Line: 20 Hz to 30 kHz (± 0.25 dB)

Mic: < 0.1% (80 Hz to 20 kHz)
Line: < 0.02%

Residual Noise (wideband, below +4 dBu output):

Unity Gain:
< -84 dB (4 Line level sources)

40dB Gain, Phantom on:
Mic: -79 dB; < -73 dB (All 4 mic level sources)

50dB Gain:
Mic: -79 dB; < -73 dB (All 4 mic level sources)

60dB Gain:
Mic: -70 dB; < -64 dB (All 4 mic level sources)

Outputs (2):
+4 dBu 150 Ω bal. (switchable to MIC level -45 dBu);
-10 dBV unbalanced

Indicators (18):
Dual-LED VU meter for each input;
COMP/LIMIT active LED; POWER LED; LED audio mix meter,
0 dB = +4 dBu
VU (dB): -20, -10, -6, -2, 0, +3; Peak Reading (dB): +8,+12

Ambient Operating Environment:
0° C to 50° C

Power Requirement:

Package Type:
Cardboard Box

Package Dimensions:
6 x 6 x 2.625 in.

Shipping Weight:
1.63 lbs.

WEEE weight:
1.38 lbs.

Tariff code:


RDL Three-Year Limited Warranty Installation of these products by the Purchaser shall constitute Purchaser’s acknowledgement and acceptance of the terms and conditions for sale and of this warranty, and shall constitute the Purchaser’s determination of the suitability of this product for the Purchaser’s intended application. Radio Design Labs, Inc., also referred to as RDL®, warrants to the Purchaser that products manufactured by RDL are free from defects in material and workmanship. This warranty applies to the period of three years from the date of shipment, except for component parts or products purchased from other sources and supplied by RDL. Such component parts or products bear only the warranty of the manufacturer thereof in effect at the time of shipment to the Purchaser. RDL will, without charge, and after written notice has been received and acknowledged by RDL, repair an RDL product if proved to be defective according to the usage of the trade, when such equipment is received by RDL at the location it designates with shipment costs prepaid by the Purchaser. RDL shall not be liable for any expense whether for repairs, replacements, material, service, or otherwise, incurred by the Purchaser or modifications made by the Purchaser to the product. No equipment shall be deemed defective if it shall fail to operate in a normal or proper manner due to exposure to excessive moisture in the atmosphere, excessive temperature extremes, improper environmental cleanliness, or any other environment not consistent with the principles of good engineering practice. In no event shall RDL have any liability for consequential damage or expense directly or indirectly arising from the use of the products, or any inability to use it either separately or in combination with other equipment or materials, or from any other cause, whether used in accordance with instructions or not. This warranty is void if equipment is altered in any way by other than RDL. RDL products are NOT intended for use in life support appliances, devices, or systems. Use of RDL products in such applications is done solely at the liability of the reseller/installer and/or end user. RDL reserves the right to change design parameters and specifications at any time without notice. The performance measurements reflect the products at the time of printing. This warranty is in lieu of all others, either expressed or implied. No representative is authorized to assume for RDL any other liability in connection with RDL products.