“Under the Hood: API 525 Compressor”

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When recording or mixing in the studio, analog compression is an essential tool that brings life and size to recorded signals in a way that plugins simply cannot replicate. There are hundreds of analog compressors out there and each one has its own distinct qualities, but if I were to choose only one for my studio, it would be the API 525. In this blog entry, we’ll be discussing the features and characteristics of the API 525, how I utilize it in recording and mixing scenarios, and why I consider it to be one of the best workhorse analog compressors.

There are a number of attributes that make the 525 a great compressor. First off, it’s a fully discrete analog compressor, so it’s built to last a lifetime and there are no IC chips or other cheap electronics that will diminish the fidelity of your signal. Its sonic imprint can be described as adding warmth, size, and density to practically any signal going through it, which is a great asset in the world of digital recording. Secondly, it’s one of the fastest compressors on the market with an attack speed of 15 microseconds and a release time of 0.1 seconds at its fastest setting. This makes it extremely effective at keeping instruments level throughout the track without sounding over-compressed, a critical attribute when it comes to the mixing process. And lastly, the compressor can be calibrated to a hundredth of a dB with a Fluke 187/189 multimeter, making it ideal for recall when mixing in the analog domain. For more info on how to calibrate and recall settings on the API 525, see my earlier blog post “Prepping a Session to Mix – Part II”

The 525 has a number of features that can take some time getting used to, but once understood, the capabilities are vast and extremely effective. There are two modes, compression (2:1 ratio) and limiting (20:1 ratio). The in and out knobs at the top of the unit control the threshold and output gain respectively. There’s a ceiling control at the bottom that adjusts the amount of compression and output gain simultaneously so that you can raise or lower the amount of compression while maintaining the same output level. An analog VU meter is on the face of the unit for monitoring gain reduction. The attack speed is fixed at 15 microseconds and there are four options for release time (0.1s, 0.5s, 2s, and 2.5s), although the release is also somewhat automatic in that lower frequencies have a longer release time than full-bandwidth or high-frequency material. There’s also a de-esser that can come in handy when tracking sibilant vocals.

I own a couple of vintage ‘70s API 525’s, as well as a newer re-issue version; I tend to use the vintage ones on vocals because they have a warmer imprint, while the newer one is a bit more transparent and is typically used on acoustic or classical guitar. I use the 525 almost exclusively in compression mode with the fastest release setting and ceiling between 4 and 8 (4 for acoustic guitar and 8 for vocals). The “in” knob is typically set to have a gain reduction of about 2-6dB on peaks and the “out” knob usually points around 2-3 o’clock.

Whether you’re tracking or mixing, the API 525 compressor delivers the analog warmth and efficient leveling capable of taking your recordings to the next level. If you want to learn more about the API 525 compressor, visit API’s website at http://apiaudio.com/product.php?id=104

Have any questions, comments, or stories regarding the API 525? What instruments have you found the 525 works well on? I’d love to hear about what you’ve found to help bring out your best sound.

Until next time,

Val Garay

'70s API 525 - 1

’70s API 525 – 1

'70s API 525 - 2

’70s API 525 – 2

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