API Audio 550A Discrete 3-band EQ in Lunch Box Format

General

The API Audio 550A Discrete 3 Band EQ is a modular tone control for the API-500 system. This unsuspecting EQ is both a real classic and a professional studio standard. With this 3-band tone control, you can adjust the frequency spectrum to 21 points with 5 possible steps. There's a band pass filter on board that you can switch on independently of the other settings and for the low and high frequencies, you can choose between peak and shelving using the pressure switch. The 550A is the original reference for testing other EQs and remains unbeaten.

API Audio 550A

The three frequency bands of this EQ each have five frequency centers that overlap and can be adjusted within the following parameters: lows at 50, 100, 200, 300 or 400 Hz; mids at 400, 800, 1500, 3000 or 5000 Hz and highs at 5000, 7000, 10,000, 12,500 or 15,000 Hz. The adjustments are made in five steps, namely: 2, 4, 6, 9 or 12dB plus or minus. With the bandpass switch you can attenuate the spectrum at 50 Hz and 15 kHz with 3dB to give a more subtle, rounder sound. The 550A is also known for its Proportional Q which, as you increase or decrease the frequency, narrows the bandwidth, so the higher the boost or cut, the narrower the Q. This allows you to make incredibly accurate adjustments.

Advantages of the API-500 Lunchbox Format

API introduced the lunchbox format. This is a modular system that lets you choose the high-quality peripherals you want that can then be easily installed into a single rack. It's known as the API-500 format. Being able to choose the components you want is one of the biggest advantages of this system. Another one is the fact that everything can be powered from the rack itself, which saves you money because you don't have to buy separate power supplies for all the parts you choose. It's also handy to have everything installed in a single rack because it's much neater and more portable too.