ART Auto-Tune Pre Single-channel Microphone Preamplifier Features: An excellent and affordable tube microphone preamp that lets you get perfectly in-tune vocals live or in the studio; Built-in Antares Auto-Tune EFX technology provides 3 stages of tuning, from subtle pitch correction to hard tuning. Mic Pre-amps boost the gain from a 'mic level' signal and can add character and warmth. Incorporating an ADC into the traditional design, the Audient ASP800 8-Channel Pre is another great option for pristine audio conversion along with a great sounding mic pre all in one package. Alternatively, browse Audient's full range of Mic Pres. For the more serious studio environment at home. Get the best deal for Art Pro Audio Preamps & Channel Strips from the largest online selection at eBay.com.au Browse our daily deals for even more savings! Free delivery and free returns on eBay Plus items!

This combination of preamp and Auto‑Tune processor could be just the thing for adding a radio‑friendly sheen to your live performances.

ART have teamed up with Antares to produce this DI‑box‑sized Auto‑Tune Pre, a mic/line preamplifier with a hardware version of Auto‑Tune built in. Clearly, such a product will hold little appeal for the DAW user as pitch correction is invariably best applied after recording, usually via plug‑ins, to allow scope for adjustment and parameter automation, but for live performance it has very clear applications. The Auto‑Tune Pre could also prove very useful for those using hardware multitrack systems that don't have the capability to run plug‑ins, as recorded tracks may be re‑processed via the line input of the Auto‑Tune Pre.

The Auto‑Tune section of the preamp, which claims a low latency of around five milliseconds, has a user interface designed to work as much like the plug‑in version as possible, and that extends to 'piano layout' note‑selection buttons on the front panel. These allow the user to create custom scales, as well as to select straightforward major or minor scales according to the key, though there's also a straightforward chromatic mode. Five user presets are available for storing the scales appropriate to specific songs, and these may be stepped through using an optional footswitch where required.

While the plug‑in version of Auto‑Tune has a fully variable control to set the speed of pitch correction, the Auto‑Tune Pre has just three speed modes, labelled Pitch Correct, Soft EFX and Hard EFX. The last two are special effects settings that capitalise on the now well‑known (and some would say overused) side‑effects of over‑fast pitch correction. Hard EFX produces the familiar hard‑quantised robotic or pseudo-vocoder sound recognisable from countless records, while Soft EFX imparts a hint of Auto‑Tune in a less obvious way.

On the mic amp side, a discrete‑component front end feeds a 12AX7A valve circuit to add a little warmth and character to the signal path. Internal step‑up circuitry boosts the valve supply voltage to well above what the power supply rating might suggest,and also supplies the phantom power. A +20dB gain switch operates in conjunction with the variable input gain control, where a pair of LEDs show signal present and clip status for level-setting purposes. A further rotary control sets the output level.

A TRS insert jack permits external processing to be interposed in the signal path between the preamp and Auto‑Tune sections, while a TRS footswitch jack socket on the rear panel provides a means of remotely bypassing the Auto‑Tune section and stepping through the five presets using a dual, momentary action (non‑latching) footswitch.

As well as the audio I/O, the Auto‑Tune Pre features a footswitch input, allowing you to remotely bypass the Auto‑Tune processing.

A 'combi' XLR/jack socket is used for the mic/line input, with the main output being present on both balanced XLR and unbalanced jack connectors. Three rear‑panel button switches select +4dBu or ‑10dBV output levels, low‑cut filter on or off, and 48V phantom power on or off. A further button functions as a power switch, with power coming from the included 9V AC power adaptor. ART quote a dynamic range of better than 104dB (A‑weighted), with the frequency response staying flat from 10Hz to 20KHz, ±1dB. The maximum output level is +24dBu (balanced).

Operation

The preamp section is quite straightforward in terms of control, so you only need to adjust the input gain until the red peak LED (which comes on 3dB below clipping) flashes only briefly and very occasionally on the loudest peaks. You may also need to engage the low‑cut switch, which will help combat vocal popping in live performance. A maximum of 66dB of gain is available if the output control is also set to full (+5dB), and that's plenty for a typical live performance using a close‑up dynamic mic.

For the Auto‑Tune section to work reliably, the mic should be positioned to pick up as little spill as possible, so the vocalist will probably need to work quite close to the mic, as excessive spill can defeat or confuse the pitch-tracking process. Individual scale notes can be toggled on or off via the note keys on the front panel, which have illuminated switch caps to show which notes are active.

When setting a simple major or minor scale, a 'key' button allows the 12 scale options to be cycled through, and a row of 12 LEDs indicates the currently selected key. A similar arrangement allows stepping through the major, minor or chromatic scale options, and the lighted 'note' buttons change according to your selection so that they always reflect the target notes for the current setting. Of course it doesn't matter what scale you select if you use chromatic mode, as the pitch is always nudged towards the closest semitone (and in this mode, allthe note buttons light up to show that they are all 'valid').

A useful setup aid is provided in the form of pitch oscillators, which can be activated by pressing and holding the button of the note pitch you want to hear for two seconds or more. There's no mention of any means of offsetting the internal pitch reference from its A440Hz setting, so if you're playing along to a non‑concert‑pitch instrument, the Auto‑Tune function should be bypassed. Pressing Store saves your setting to the current Preset, as shown by the LEDs on the right-hand edge of the panel. The state of the bypass switch is also saved with each preset.

Tested with my acoustic guitar combo's mic input and a dynamic microphone connected to the Auto‑Tune Pre, I was a little disturbed to be greeted by a low level, but still annoyingly audible, background hum/buzz that wasn't there when I plugged the mic straight into the combo. I made sure that the Auto‑Tune Pre and its cables were well away from the amplifier, and other powered devices in the vicinity were also unplugged to avoid interference, but the buzz remained unless the Auto‑Tune Pre was switched off. Oddly enough the level of buzz changed very little when the output level switch was operated, but with the output level set to +4dBu, the buzz would almost certainly be inaudibly low in a live situation, as long as the mic gain was set sufficiently high.

In all other respects the unit worked exactly as promised, with a clean, solid‑sounding pre‑amp and effective Auto‑Tuning. In the normal pitch correction mode, the correction rate is fairly slow, so natural inflections aren't usually affected, unless you are into making very slow pitch glides. There's a sense of chorusing when you hear the pitch-corrected vocal alongside your natural voice, but nothing too off‑putting. The middle setting is more assertive, but still allows most of the singer's natural articulations to come through. This introduces some familiar Auto‑Tune fast‑slurring artifacts, but everything still sounds more or less human with a contemporary edge not dissimilar to that heard on many pop records.

Go to the Hard EFX setting and the pitch correction is so fast that most of the natural articulation is stripped out, leaving you with a hard, pitch‑quantised sound, again corresponding to the kind of thing heard on some records — Cher's 'Believe' being the best-known example. On these faster settings more noticeable chorusing effects can be heard as the shifted sound interacts with the sound of your un‑amplified voice. If that is too off‑putting you may wish to arrange for non‑pitch‑corrected monitoring!

Conclusion

Other than a little background hum/buzz, which can be largely alleviated by being careful with your gain and output level settings, the Auto‑Tune Pre works exactly as it should, delivering the classic Auto‑Tune processing in a very easy‑to‑use manner. In addition to its vocal applications, the process can also work well on certain instruments, such as sloppily played cello or violin, when used in a pop context. There are also special effects galore to be had by experimenting with scales containing very few notes. I can't get too excited about the Auto‑Tune Pre as a studio processor, at least not for DAW users, but for live performance or the hardware studio operator it has a lot to offer.

Alternatives

The TC Electronic Mic Mechanic puts automatic pitch correction into a pedal format, along with a mic preamp, some auto EQ/dynamics functions and a selection of delay/reverb effects. It has variable correction speed, but only operates in chromatic mode.

Pros

• Easy to use.
• Can store five user settings.
• Classic Auto‑Tune sounds, both natural and 'hard'.

Cons

• Some background noise audible in some setups, though this should be unnoticeable in live performance.

Summary

A practical implementation of Antares Auto‑Tune, in a compact mic‑preamp format that is well suited to live-sound work.

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This two‑channel tube preamp offers a range of useful features, and all for a very modest asking price. Is it too good to be true?

ART have a long‑standing reputation for delivering good, affordable audio processors, and their Pro MPA2 seems set to continue that tradition. Essentially, this device is a 2U-high, two‑channel mic preamp with switchable 48V phantom power and continuously variable input impedance. The latter is something that can have a significant effect on the sound of the connected microphone; in particular, many dynamic models, including passive ribbons, prefer to see a higher impedance.

Overview

Art Auto-tune Pre Tube Microphone Instrument Preamp Single Channel 3

The Pro MPA2 can be set up for dual‑mono, conventional stereo or M/S (Mid/Side) operation. In this last role, channel one is used for the 'Mid' mic and channel two for the 'Sides'. Further tonal variety is offered by the ability to run the 12AX7 valves at low or high anode voltages.

The Pro MPA2 certainly feels solid — it was rather heavier than I expected it to be when I lifted it — and the front panel looks stylish, with its detented, somewhat retro‑styled knobs and large, backlit, moving‑coil VU output meters that have adjustable calibration trims. Further LED bar-graph meters, labelled Tube Warmth and set between the VU meters, show the amount of tube drive being used. While the mic inputs and balanced XLR and TRS jack outputs are on the rear panel, a high‑impedance instrument input is conveniently positioned on the front panel, this taking precedence over the mic input when connected. A rear‑panel button allows the output level to be set to +4dBu or ‑10dBv, and the meter calibration automatically follows this setting.

Art Auto-tune Pre Tube Microphone Instrument Preamp Single Channels

The mic input is a solid-state design, with a rotary control to set the initial gain. This has only a 40dB range, but an extra 20dB of gain can be applied before the tube stage. Having an extra gain boost selectable in this way helps the preamp to run at lower gains while still maintaining a high signal‑to‑noise ratio, as many affordable mic preamps only deliver their quoted EIN figure when set close to maximum gain. A combination of the input gain and this 20dB 'boost' can be used to drive the tube stage as hard as you feel appropriate. A further 10dB is available via the output gain control, so there's an overall maximum gain of 70dB. (The manual claims 75dB with everything flat out, but I'm not sure where the extra 5dB comes from!)

Next to the input gain control is the one that governs input impedance, which ranges from 150Ω to 2.4kΩ. To keep the lows under control, there's a smooth, 6dB/octave low‑cut filter that can be swept from 10Hz to 200Hz. Four illuminated buttons beneath the VU meter are used to select 'normal' or +20dB of gain, phantom power, high or normal 'plate' voltage, and polarity inversion.

A further button mounted between the channels selects the M/S decoding matrix, so that an M/S mic pair fed through the unit will produce a standard stereo signal at the output. At the extreme right of the unit is a 'stereo' button that allows the rightmost output‑level control to function instead as a stereo balance, while the leftmost output‑level control operates as a master stereo level control.

The technical spec looks suitably impressive on paper, with a frequency response extending from 15Hz to 48kHz (+0, ‑1dB) when the valve anode‑voltage is set to normal. An equivalent input noise for the mic input is quoted as ‑129dBu A‑weighted, translating to a dynamic range of better than 110dB, again A‑weighted. Both mic inputs can accommodate signal levels of up to +10dBu before clipping, whereas the maximum instrument level is +17dBu (800kΩ impedance). The output stage can handle up to +27dB on the XLRs, and has a low 47Ω impedance, which is suitable for driving long cables.

ART Or Science?

So how does it sound? My first test was with a capacitor mic and, as expected, the input impedance made very little difference. (The active circuitry in the mic buffers the signal, making it less dependent on load impedance.) I set the input gain near maximum and used the output level control to achieve a decent recording level without switching in the 20dB boost. Only one or two of the tube drive LEDs came on, and this arrangement produced the most transparent, natural‑sounding result.

Engaging the boost and adjusting the input gain to push the tube-drive LED meter around halfway introduced a subtle warmth that I found quite usable, but as I pushed things harder to get the meter bouncing around close to the top, the sound became noticeably overdriven. This degree of drive would probably only be used on certain instruments, or maybe as an obvious effect on some pop and urban vocal styles.

Bringing the drive down to a low level and switching on the high tube-voltage brought about a subtle thickening of the sound, which, again, I found musically useful. In combination with a higher drive level, the sound again became progressively warm, then thick, then quite distorted as the pre‑tube gain was increased. At modest drive levels, this can be useful in bolstering a weak vocal, but I'm not a fan of vocals driven to the point where the distortion is obvious, so probably wouldn't venture much more than halfway up the drive LED meter.

Using a passive ribbon mic, the output level got significantly louder at the higher end of the impedance dial, along with a subtle brightening of tonality. The variable input impedance will be of particular benefit for anyone working with such microphones.

Lasting Impressions

The rear panel of the MPA Pro2 sports balanced analogue inputs and outputs, and +4dBU/-10dBV switching.

Despite its relatively low cost, the ART Pro MPA2 delivers on both sound quality and versatility. It doesn't match the transparency of some of the more costly high‑end preamps, but it gets close enough for most home studio applications — and out-performs many audio interface on‑board preamps — while also having the ability to produce very controllable tube character. The two tube‑voltage options provide another subtle but useful variation in tonality, and the variable input impedance is invaluable for use with passive ribbon mics or other insensitive dynamic models.

I was also pleased to see the M/S facility built‑in, as M/S recording is a very useful technique that's often neglected in the smaller studio; having on‑board decoding means that anyone with a suitable figure‑of‑eight mic plus one other mic can have a go and hear the benefits of this approach for themselves.

You may not feel you need an additional mic preamp if you have some built into your audio interface already, but I find that many of the mic amps built into audio interfaces, especially at the more affordable end of the market, are susceptible to picking up digital interference from the Firewire or USB circuitry when run at high gain settings — and this, again, is a particular problem when using passive ribbon mics. The MPA Pro 2 would be an ideal remedy for that particular disease.

Verdict

In a nutshell, the Pro MPA2 is great value for money. Not only does it sound pretty good, but it's one of the few budget tube preamps to run the tubes at a suitable voltage, and it's extremely versatile, with several useful tricks tucked up its sleeve that many of its competitors lack.

Alternatives

The SPL Gold Mike costs only slightly more than the Pro MPA2 and is still top of my favourites list for affordable tube preamps, though it doesn't have as many features as the Pro MPA2. Specifically, there's no variable impedance and no M/S decoding. TL Audio's mic preamps also perform consistently well, but they tend to be more expensive.

Pros

• Keenly priced.
• Good basic sound quality.
• Useful extra features, such as variable input impedance and M/S decoding.
• Switchable valve voltage and variable drive provide a range of useful 'warmth' options.

Summary

The Pro MPA2 is a strong performer, offering better sound quality than most built‑in 'interface' mic preamps, but it is the extra features that may swing the sale for some users, especially those wanting to use passive ribbon mics or undertake M/S recording.

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