Rane Mojo MH4

If you don't need separate mixes for each musician, the Mojo MH4 may be everything you need in a headphone amp, says Paul White.

For years you never see a headphone amp, then a whole bunch come along at once. This month's offering is part of Rane's Mojo series and is a full rack‑mounting, 1U device, powered by a mains adapter (which is included). Just as the Samson Q5 — which we reviewed in March 1997's issue — did, the Mojo MH4 keeps things simple in order to maintain an attractive retail price. In this case, you get four independently controlled stereo phone outputs fed from a single stereo source. The inputs are on two balanced TRS jacks, though unbalanced feeds may also be used if you simply plug in mono jacks. A yellow power LED accompanies the front‑panel power‑on button.

So long as you keep your eyes on the clip LEDs, setting up is as simple as plugging in and turning up the level.

A globally acting mono switch is fitted to the front panel, allowing both phones to be fed from a mono mix of the two inputs, and each output (quarter‑inch stereo TRS jack) has its own overload LED — very useful when you're trying to figure out whether the distortion you're hearing is due to overloading the MH4, the phones, or your ears! There are no linking jacks on this unit so, to feed two units, you'll need to use split leads, and the available amplifier power is a maximum of 200 milliwatts per output, enabling headphones of 32Ω and upwards to be used. The optimum range is 32‑150Ω, as higher‑impedance phones will tend to produce less level, though phones up to 600Ω may be used. Because lower‑impedance phones produce a much higher sound level than high‑impedance phones when driven from the same voltage, output settings may vary radically depending on the type of phones used. The frequency response extends from 20Hz‑20kHz; the clip LEDs come on 3dB before clipping, and the maximum gain is +26dB.

In Use

The sound quality from the Mojo MH4 is fine both with open and enclosed headphones, though with two different pairs of phones some distortion was audible just before the clip LED came on, suggesting that the phones were calling it a day at about the same time as the output amps were. However, I'm convinced that I get more clean level out of my home‑made headphone amps based on 2W‑per‑channel integrated amplifier chips, so maybe some distortion is audible before hard clipping takes place. For most recording purposes the level is adequate, but I felt that the maximum level was a little short of what some drummers might demand — regardless of how bad it is for their ears! (The same is true of the Samson Q5, reviewed last month, though.) However, the manual does list the maximum SPL that can be expected from several different types of popular headphone, and this ranges from 107dB‑126dB, which is seriously loud. There is no master input trim control on this unit, but I can't say I missed it. So long as you keep your eyes on the clip LEDs, setting up is as simple as plugging in and turning up the level.

Summary

The Mojo MH4 is an affordable 4‑way headphone amplifier for use in situations where it's okay for each performer to receive the same mix. I like the rackmount format, the build quality leaves no cause for concern, and the Mono button is useful. For those who prefer to wear one phone on and one phone off, the stereo inputs enable you to feed a single send into just one input so that the other remains silent. Alternatively, if you need a mono feed in both ears from a single input, the Mono button does the trick. I'm still not convinced that the output is clean enough at very high volumes when you're using low‑sensitivity, high‑impedance phones, but other than that, the Mojo MH4 works fine.