Palmer PMB-L Merge Box
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Essential Information About the PMB-L Passive Mixer Box
Essential Information About the PMB-L Passive Mixer Box
- Passive line summation on 2 channels: two symmetrical XLR/f inputs mixed into one symmetrical XLR/m output, without power supply.
- Galvanic isolation on the upper input: ideal for avoiding ground loops and securing interconnections between equipment.
- Designed for field use: compact aluminum enclosure, ground lift switch, easy integration into a mobile rack or control room.
- Immediate applications: combining two mixing consoles into a single final stage, or obtaining a reliable mono signal from a stereo source.
Manufacturer Information
Palmer
https://www.adamhall.com
info@adamhall.com
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Adam Hall GmbH
Email: info@adamhall.com
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A Classic of Passive Summation: When Simplicity Makes the Difference
The PMB-L belongs to the family of passive mixer boxes (also called combiners or summing units) intended for line-level signals. The concept is simple: cleanly sum signals without an active stage, using a resistor matrix. This approach, proven in sound reinforcement, broadcast, and fixed installations, is appreciated for its robustness and predictability: no gain to adjust, no risk related to power supply, and stable behavior over time.
With its two channels, the PMB-L positions itself as a versatile tool for configurations where one needs to combine or re-route audio lines without complicating the signal chain. It meets the typical needs of technicians seeking a reliable, compact, and quick-to-deploy solution while maintaining a balanced connection on the output.
Who Is the PMB-L For and When to Use It?
The PMB-L is intended for users handling line-level signals in professional environments: sound engineers, live service providers, stage managers, studios, theaters, houses of worship, and integrators. It is particularly relevant when multiple sources must feed a common destination without using an additional mixer or occupying available inputs on a console.
Typical use cases include: combining two mixing consoles (for example, a front-of-house console and a monitor console) into a final stage, performing a mono summation from a stereo signal, or combining line outputs in a broadcast chain where simplicity and reliability are prioritized. In these scenarios, the passive design helps limit failure points while maintaining clean and standardized XLR wiring.
Technical specifications
| Number of channels | 2 | Type | Box |
| Rackable | Yes | Color | Natural |
| Category | sound reinforcement accessory | Nominal mode power consumption (Wh) | 0 W |
| Function | signal combiner | Maximum level (harmonic distortion of <0.5% @ 35 Hz) | +20 dBu |
| Mixing type | passive, for line-level signals | Typical attenuation | 6 dB |
| Per channel | 2x balanced XLR/f inputs to 1x balanced XLR/m output | Ground switch | yes |
| Signal mixing | via resistor matrix | Dimensions | 110 x 125 x 38 mm |
| Isolation of the upper input | galvanic, via transformer | Weight | 585 g |
| Output signal transmission | balanced | ||
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Questions frequently asked
Can two stereo signals be summed into mono with the Palmer PMB-L?
Its 2 channels each feature 2 balanced female XLR inputs connected to 1 balanced male XLR output. A mono summation of two line signals can thus be achieved on one channel.
What XLR connectivity does this summing box offer?
Each channel combines two balanced female XLR inputs and one balanced male XLR output. The output maintains a balanced connection.
Does the PMB-L require a power supply?
The passive design using a resistor matrix requires no power supply. The nominal power consumption is specified as 0 W.
What level loss is expected with this passive merge box?
A typical attenuation of 6 dB is specified. The maximum allowable level reaches +20 dBu, with harmonic distortion under 0.5% at 35 Hz.
How to reduce a ground loop between two audio devices?
The upper input is galvanically isolated via a transformer. A ground lift switch allows intervention in case of hum related to ground. The aluminum housing measures 110 x 125 x 38 mm and weighs 585 g.
