Sound on Sound recently ran an article about a microphone preamp shoot out. In it, they tested out a number of different preamps using a modern version of a player piano and some great mics. The resulting recordings were then posted online for everyone to vote. Well to everyone surprise the preamp voted favourite by the readers with each mic – except the ribbon mic – was the Art Pro MPA II.
Clearly this preamp is not one that will make you sell your 1073′s, and as Sound on Sound reminded us, if you use a preamp properly you will get good results out of almost any one you choose. But, let’s not get into comparing hi-end and budget preamps. Let’s just take a look at a pre that has gained some recent attention.
Good sized knobs give you control over the usual array of parameters, as well as some less common features that are typically reserved for pricier units. The top row of controls have a gain pot which amplifies the signal before hitting the tube, an impedance control which can affect the tone on dynamic or ribbon mics, and an output control to tame the signal before hitting the A/D (I will go ahead and assume you are recording digitally). To the far right you will also find a Stereo / Dual switch which will link the output control of both channels to channel one’s output pot, and turns channel two’s output control into a pan pot. Neat.
Along the bottom row you have a High Z input on each channel (try driving a bass hard with this) followed by a low-cut filter. This is a tame filter by most standards as it’s only a single pole filter (6 dB/octave) so don’t hesitate to use this before you get in the box. Each channel also has four buttons in common – a +20dB gain, +48V phantom power, Plate voltage, and a phase inverse button. The +20 dB gain gives you an extra boost before the signal hits the tube, allowing you to get a driven tube sound on quieter sources. The phantom power and phase invert are self-explanatory, but feel free to google them if you want to know more. The plate voltage is a great feature which changes the behaviour of the tubes, giving you a cleaner signal with a higher headroom. Center on the unit you will also find the Mid/Side Matrix button which will decode your mid/side mic setup into a stereo left and right signal.
In the middle of the unit stands the metering, which includes two VU meters for the output levels (0 VU = +4 dBu) and an 8 LED segment tube warmth meter which lets you know how hard the tube is being hit by your signal.
A quick peek inside reveals just what one might expect. A clean, well laid out circuit board and two 12AX7 preamp tubes. The tubes are a basic Chinese 12AX7 and are a good place to start when looking at modifying this mic pre. For the purposes of this review, I will be using the stock tubes. All samples have been made after the preamp has warmed up for at least a half hour, which is where I stopped noticing a difference (or maybe just got a little impatient).
The following was a DI’ed guitar signal provided by Kennybro from the GearSlutz forum fed into an Epiphone Valve Jr Head > Traynor DarkHorse 2×12″ Cab > SM57 > ART Tube Pre > 003 Line input
How Does It Sound?
In use, I found the pre to be pretty straight forward to operate. While recording I always had the +20 gain button pushed in. It makes sense though, why else would I choose a tube pre unless I wanted to get some tube sound? The addition of the tube warmth meter made it easy to set my gain control. With it tickling the yellow I knew I had some headroom before things would get a little out of control (see my driven sample at the end of the article).
I recorded a handful of sources and was pleased with the overall sound quality – nothing really stood out to me as an issue. The HPF being 6bd/oct meant that you could throw it on and take a tasteful cut out of the low-end junk without worrying about destroying the body of some lower notes. The plate voltage did in fact give more headroom before the tube saturated, but I found I never really wanted that. Perhaps if it was my only preamp, that might be a benefit – but for me it was a feature just for the sake of having another item on the features list. The inclusion of the +4 / -10 output was another feature I would never use, but provides a good service to those running directly into some consumer gear-like computer line-inputs, iPhones, etc. One thing to note is that adjusting the input impedance will cause a change of gain, so be mindful of this as you adjust your impedance.
The impedance is switched from the lowest setting or 150 ohm to the highest 3000 ohm part way through this clip. Can you hear where?
At first when listening back I could hear very little difference between the impedances. Which isn’t too surprising since the 300 oHm output of the SM57 is right in the basic range of this preamp. Honestly I was expecting more difference (you will find a greater difference on a ribbon mic than dynamic). However, as I was about to give up on finding a difference I noticed a recording I had done a few days earlier as a warmup with my own playing. At the end I hit a sudden chord and the lower impedance had far more bite to it. Cool. So while this guitar part may not have been the best for demonstrating the variable impedance, there is a difference. Play with it!
All and all I was impressed with the preamp. It had pretty good overall sound quality on the sources I recorded. Due to fact that the other material recorded has not yet been released, I could only provide examples of the guitar track presented here. While it would not be my first choice of pre, with a couple of higher end options being my go-to’s, it would always be a consideration. The combination of an expansive feature set and a low price point make this a no brainer for anyone looking into an inexpensive pre.
The ART Pro MPA II driven a little harder into distortion