The Stam Audio SA-550A EQ with “proportional Q” circuitry
The original 550 unit was designed in the late 1960s by Saul Walker, and became a studio standard in API consoles and other custom designs. Due to the way it was built, it exhibited greater phase coherence than its competitors, which is essential for obtaining a tight low end. This made the 550 EQ a favourite on bass and kick drums, but always found a use regardless of the instrument due to its musical “proportional Q” circuitry. Its unique sound is attributed to the way the bandwidth adjusts as the amount of EQ applied is increased, as well as the 2520 op amps used in the original units.
The 550A differed slightly from the original, benefitting from five frequency selections on each of its three bands. Each can be boosted or cut up to 12dB whilst maintaining musicality at every step. The high and low bands can be peak or shelf filters, controllable by a dedicated switch. Additionally, a bandpass filter is included, which operates between 50hz and 15khz.
If you’re wondering how this vaunted “proportional-Q” feature is applied practically, it simply means that the greater the boost applied, the tighter the Q setting, giving this unit an identifiable character not seen in other EQ’s.
Although the Stam 550A can be used on any instrument, it really shines in applications where a solid, tight low end with plenty of energy is desired. Drums sound punchier, bass sits better in the mix, and guitars tighten up beautifully with even a little 550A treatment.
The SA-55A is a dual channel unit in a 1U chassis. Each channel has three frequency bands, with five selectable frequency centers for each band, as well as the filter options present on the original. To get that authentic punch, we use two Altran 2503 output transformer replicas which are made in the US. It features two Stam SA-2520 op amps, as well as vishay capacitors and carbon ohmite resistors. You may find that online reviews of Stam products are extremely favourable when compared to other replicas. This is a reflection of this meticulous approach to component selection.
100% satisfaction guarantee – if you don’t love your SA-550A, we’ll refund you
If you’ve used an original 550A before, we’re extremely confident the SA-550A will put a big smile on your face every time you use it. However, if you’ve never touched the original before, as gear lovers ourselves we understand that the only way to really know if this equalizer is right for you, is to put it through its paces. That’s why the SA-550A comes with a 30 day money back guarantee. This allows you to get it into your rack and see how it impacts upon your recordings. If you love it (and we think you will!), great…keep the unit and create amazing music with it. If not, no problems.
Just send it back to us and we’ll fully refund your purchase. And don’t worry, whichever way you decide to go we will remain friends.