Gear Review: Fostex AR501 Mic Preamplifier

    Fostex are a company that have always been in and around the field audio recording market. With their industry leading portable DAT recording machines and excellent preamps they have always historically brought good products to market.
    The Fostex AR501 is a single channel (although capable of being ganged into a stereo configuration) microphone preamp which can provide +48V Phantom power which can run off a single AA battery. The concept behind the product is a high quality preamp that can be used quickly and easily with small camera setups on cameras that lack proper XLR inputs. However Fostex have had the forethought to include an XLR direct output should you require it (I do!).



Control

    All of the controls for the device are situated inside the battery compartment, right next to the battery. They are all just small switches, allowing you to make a number of menu selections without having to go through the manual. You've got individual controls over input type (line/mic), phantom power (on/off), HPF (160Hz, 80Hz, off), mic level (H - - L), attenuation of the unbalanced out (on/off) and power (on/off).
    Those basic functions are pretty much all anyone would need from a simple mic pre. I don't have any further requirements from it and it really does function very well indeed. But if we delve a little deeper into the manual you'll find that there is a little hidden functionality in there. There is a Low Power mode which switches down the operating voltage of the circuitry to half of normal. This has the caveat that you then get a reduced phantom power down to 24V, and also possibly some slight reduction in the overall headroom. I found no problem with the headroom, but in case of scenes requiring a wide dynamic range I'd always run in full power mode anyway.

Gains
    The gain control for this preamp is not the traditional knob that you'd find on most kit. It's just on of those small stepped switches (with four steps) marked from H to L. The manual gives further insight and describes L as +24dB gain, followed by +34dB, +49dB and finally H which delivers +64dB of gain. These are good, well thought out steps giving enough variation in level to accommodate every mic that I have. Generally I found the +64dB step to be a little on the noisy side, but I never had the need to use that amount of gain anyway.

Output

    The AR501 gives us two output options, there's simple balanced or unbalanced. Both work as you'd expect really. However a quirk in the electronic design means that the XLR balanced output will only work if the input is set to mic. The unbalanced output also has the added functionality of being attenuable from line to mic level.

Gangs
    Another cool feature for those using it with anything other than pro audio gear is that two of these units can be operated as a stereo pair designed to feed a 3.5mm stereo jack with either mic or line level audio. This means you could run two channels of great quality audio into the stereo mic input jack on a DSLR using pro level mics or radio mics, or alternatively if your portable recorder has the same powered mic connector then you can do the same. My backup recorder is currently a Roland R26 portable, with these two boxes I can add two more XLR inputs making it a (nearly) proper four channel recorder, which would be much more suitable for low end film production.
    To set up this function all you have to do is plug one units unbalanced out into the others R-IN socket. The unit with the R-IN being used then becomes the output feed for stereo functionality. Every AR501 comes with a short coiled 3.5mm cable so that you can use this straight away without any additional parts. There's also a handy rail connection that you can use to stick them both together so they're not rattling about all over the place.




Usage
    Given all of the above features you get in this little box I've come up with a few usage scenarios that range from the broad to the slightly more specific:

- Mic input for DSLR camera (also stereo input)
- Additional XLR mic inputs for portable recorder such as Zoom H1 through H6 or similar.
- Stereo balanced XLR input for Sony PCM D100 (low cost DSD recording with proper inputs)
- Additional mic inputs for pro recorder (small channel counts such as 744T)
- Phantom powered mic input for radio beltpacks. (Add radio capability to your boom!!)

Power
    As a small and portable unit that his is, it runs off a single AA battery. Pretty simple and readily available anywhere on the globe, which is perfect for those jobs away from home. The battery life on AA batteries is pretty decent getting anywhere from 10 hours with cheap alkaline AA's in full power mode all the way up to 18 hours from high capacity rechargeables in low power mode.
    It also has an extremely handy DC input on a microUSB connector, which means these can run on any USB power pack suitable for phones or using Hirose-USB adapters from your current battery solution if you're running those in your recording bag. The DC input won't charge the AA batteries, but it will automatically switch power sources when the DC power falls below a certain threshold.

Verdict
    The Fostex AR501 always intrigued me as a product since I saw it listed at it's full retail price, but I was wary of the product at that price because it seemed to me to be a risky investment. It turns out that it was actually a really good product all along, with a balanced set of features for a wide set of usage scenarios. The mic preamps are clean and the stacking features are an added boon. It's also lightweight making that wireless boom rig I mentioned even more viable with the right kit up there.
    My only gripes with this preamp are that firstly, there's no limiter on the input. That would be a really nice feature on a preamp originally priced at £300 or so and make one man bag recording even easier. And secondly, although not much Fostex could do about this, they're not Sound Devices 7xx input channels. (If Sound Devices were to make a lovely, compact, two-channel mic input module for the 744T I'd probably buy it straight away.)
    All in all I've had a very positive experience using this mic preamp and ha
ve added these two to my standard recording kit paired with my Sound Devices 744T giving me four mic channel recording on set.


ADDITIONAL NOTE: This handy little box is now discontinued by Fostex and suppliers are now selling off the remaining stock. It could be that Fostex has a newer higher performance model coming out soon or they just never sold enough to make it viable to continue manufacturing it. Either way they are going cheap over at B&H photo in America so they work out after tax and shipping at about £80 a piece instead of their original price which was a slightly eye-watering £300.