Fostex 3070 Compressor/Limiter Review

One of my close buddies picked up a Fostex 3070 Compressor/Limiter today for $50.00 off of a Craigslist deal and promptly handed it over to me for inspection and testing.  To be honest, my experience with analog compressors is fairly limited; I have used EL Distressors in the past but beyond that, my knowledge is quite limited.  I know what "should" work in theory and what settings might be good for certain genres of music, but I really had no idea what to expect here.

After a cursory inspection of the unit, which revealed it was manufactured in 1982, I read the manual (available online here) cover to cover.  I realized a few things right off the bat -- this is a VCA stereo compressor, it comes with an included noise gate, and side-chaining is completely possible.  The rest of the manual is surprisingly helpful... there's really no fluff here like with most modern manuals that are filled with useless garbage.

The next step was to grab a few TRS patch cables and get the 3070 hooked up to my Mbox 3 Pro.  It took me a minute to figure out how to set it up on my mix bus for stereo compression/limiting with real-time monitoring.  This is what you'll need to do if you're in this situation with similar gear:

1. Hook up your studio monitors to Analog outs 1 & 2 (this is how I always have mine)
2. Send the signal from the Mbox via analog outputs 3 & 4 into the L & R inputs on the 3070
3. Take the processed signals (L & R) from the 3070 and output into any two line inputs on the Mbox
4. Open up the Control Panel on your computer and go into your Mbox's driver settings
5. Go to "Setup" --> "Output Setup"
6. Change "Control Room Assignment" to None and uncheck the "Master Vol." checkbox.  This will ensure the audio can pass through outputs 3 & 4 to your analog outboard gear at full strength while still retaining full monitoring capabilities through 1 & 2 to your monitors.  The volume knob on the Mbox is now only affecting the monitors and not the signal going to your compressor.
7. Create two (2) aux input tracks and set the inputs to Analog 1 & 2 from your Mbox.  Make sure the little push buttons on the front of your Mbox are pushed in to trigger the signal from the rear of the Mbox if you're using Line 1 & Line 2.
8. Route all the live tracks in your session to Analog 3-4.  This is the final step, as it'll take all the session audio, send it out to the 3070 in stereo, where you can make manual analog adjustments... and the processed analog signal goes back in through your line inputs and is monitored in real time.

I know this looks like a lot, but it only took me a few minutes to get it all set up.  I'm sure it won't take you long either.

Once everything was hooked up and powered on, I was excited to start turning the knobs and hearing the results.  I quickly realized this compressor has a nice color to it -- while it's fairly transparent, it adds a nice analog saturation while smoothing out the mix.  Moreover, it goes from very little and subtle compression all the way to super crushing pumping.  Check out the quick mix/video I put together below showcasing the difference between a basic instrumental rock mix without the 3070 versus with the 3070:

The control element (the gain-reducing VCA circuit) is familiar, albeit impressive.  I have always leaned towards optical compressors, but this VCA unit has a nice wide range of effective use, unlike some others I've heard where there's a very small window of opportunity between no compression and too much compression.

The circuit is controlled by pulse width modulation, which is moderated by an electronic switch that opens and closes at a rate of 200 KHz.  According to the user manual, by varying the length of time this electronic switch is open or closed during each cycle, signal energy is reduced without distorting the program material.

One of the touted benefits of this design is lower distortion, especially in the lower frequencies.  The Fostex 3070 was engineered to be very effective when under high demand without introducing exorbitant pumping and breathing effects in the low frequencies, even when the attack time is set very fast.  In testing this out myself, it seemed to be more or less true -- I get much more pumping and breathing from the BF76 plugin on Pro Tools, anyways.

By the way, as a guitarist, one of the most hilarious parts of this whole experience was reading page 14 of the manual.  Fostex is describing how to use the side chain feature on the 3070, and they go on to say:

Consider the following use of the detector circuit: Suppose you want a keyboard to come up in level as soon as the guitar solo ends (and who knows when that will be)...

This is actually in the manual.  Rofl.  Why aren't modern manuals this entertaining?

I'll try to post up more material with this thing in the future so you guys can continue getting a sense for its capabilities.  Thanks and peace out for now!