Paul White tries to establish whether a separate mic preamp really does make a difference, using the MX2, the latest in the LA Audio Lite range of signal processors.
When every mixer you buy comes with built‑in mic preamps, you might wonder why you should fork out around £250 for just two mic amps in a box, especially when the ones available in even some of the cheaper mixers tend to be pretty good these days. There are occasions on which you might need a couple of high‑performance mic amps without having to cart around the rest of the mixer — live stereo recording is one obvious example — but the subjective sound of equipment like mic preamps also plays a large part in deciding which to use. LA Audio's MX2 is based around a transformer circuit, and a great many recording engineers still prefer the sound of transformers. Like valves, transformers tend to introduce that indefinable something to the sound, making it seem warmer and more transparent, and they also help simplify the design of a mic amp that behaves well at all gain settings, rather than just at the extremes.
The MX2 offers absolutely conventional facilities insofar as each channel has switchable phantom power, a 20dB pad, and a phase switch, but there's also a sweepable 12dB/octave, low‑cut filter that can be set anywhere between 25Hz and 250Hz to remove unwanted LF signal. This is particularly useful when recording vocals, as many environments suffer sound leakage at very low frequencies, and as these frequencies are well below the fundamental of human speech, they can safely be removed without affecting the vocal tone.
An Input Gain control provides up to 60dB of mic gain, and a clip LED is fitted to warn of impending clipping on signal peaks. A further gain control sets the output level from the mic amp, and an 8‑section LED level meter gives a useful indication of how much signal is present at the output. Both the Phase and Phantom Power buttons are accompanied by green status LEDs, and the main outputs, which are fully balanced, are doubled up on both TSR jacks and XLRs for convenience. The mic inputs are conventional XLRs.
Power is provided via an IEC mains lead, and the whole package is housed in a substantial, 1U steel rack case, tastefully finished in LA's deep green livery. Internally, all the circuitry for both channels is mounted on one large circuit board, and both the standard of construction and components is very high. Extensive use is made of ICs, both in the audio path and for metering, and the output stage is electronically balanced — although the designers have resisted the temptation to include M&S decoding, which I would have found useful.
As expected, the unit delivers a clean and apparently honest sound, with no obvious vices, plenty of headroom, and predictable operation. The slightly rubbery feel to the control knobs makes them easy to use, and the uncluttered front panel keeps operation very simple. I also like the facility of having a variable low‑cut filter, rather than the more common in/out roll‑off below 100Hz or so. There's no apparent coloration from the transformers at all, but the sound is well‑balanced and uncongested, with a pleasant openness at the top end, suggesting that the transformers might be making a benign psychoacoustic contribution. Transformer nonlinearities can make subtle modifications to the harmonic structure of a sound, as well as affecting the phase relationships between the different components that make it up, and providing these effects are subtle, the result can make the sound appear even cleaner than it really is. Again, this isn't unlike the mechanism behind the tonality of valves.
Given that this is a transformer‑coupled design, and that transformers aren't the cheapest of components, the asking price for this mic amp starts to look more realistic — indeed, you can pay a lot more than this for a mic amp that doesn't really perform very much better. As an Output Gain control is provided, it's possible to use the MX2 for recording directly to tape without having to go through a mixer, and by keeping the signal path short in this way, significant improvements in sound and background hiss can be achieved. On balance, this is a well designed, very simple product that allows the user on a budget to experiment with esoteric recording methods, without having to pay esoteric prices.
- Good audio performance.
- Clean, intuitive styling.
- Includes filter and output level controls.
- No M&S (Middle & Side) decoding.
A well‑designed, versatile mic preamp for both studio and mobile applications. The inclusion of a filter and an output level control makes the MX2 particularly suitable for 'minimum signal path' recording.