Traditionally, all ribbon microphones were passive. They needed no phantom power and were of a simple design consisting of a thin aluminum ribbon, two magnets and a transformer. That’s it.
Though passive ribbon mics have always been known for their incredible sound, they also come with certain requirements needed to reach their full sonic potential. This mainly involves using a very high-gain, high-impedance mic preamp — characteristics that many modern preamps lack.
Pairing a passive ribbon mic with a preamp that has a low input impedance can have a negative effect on the low-end, transient response and overall frequency response of the sound. A high-gain, high-impedance preamp allows a passive ribbon mic to operate at its peak performance level.
Of course, rules are made to be broken. Some artists like using low impedance preamps creatively to change the color and tonality of their microphone. This is why we design different types of mics so they can used creatively by their owners.
For many working musicians on the road — who never know what kind of console or preamp they will be plugging into on any given night — mic preamps can be a problem. Something needed to be done to help these musicians overcome the problem.
Enter Active Ribbons
Since 2008, AEA has been creating active versions of ribbon mics to circumvent these preamp requirements. Active microphones are the same as passive microphones with one major difference — they have internal electronics and a custom transformer that boost the mic’s output level and maintain a consistent impedance over the entire frequency spectrum. To operate this circuitry, active ribbons require standard 48-volt phantom power.
The mic’s internal electronics have a few key benefits that give them more flexibility over their passive brothers and sisters. This includes 12dB more gain, a better signal-to-noise ratio and a consistent impedance without regard to the type of external mic preamp used.
In certain instances, long cable runs from a passive ribbon mic to a preamp can cause noise issues as well as impedance problems. In scoring stages, often times the preamps are in the recording space near the microphones and musicians minimizing this interference. This isn’t always a practical solution. Active mics do not have this problem because of their built-in electronics.
For many years, all ribbon mics have come with a warning not to use phantom power. That has now changed. Accidentally engaging phantom power in one of our mics is not normally a problem.
However, if the ground pin is shorting an XLR cable or if a TRS cable is patched to the input of a passive ribbon mic while phantom power is engaged, this can blow up a ribbon! Active electronics protect the ribbon from blowing up if phantom power is accidentally engaged while patching a TRS cable on the input of the mic. While the electronics protect the ribbon, we still recommend avoiding hot-patching while phantom power is engaged because it is hard on the electronics.
Active microphones can be used with any preamp and their frequency response will sound very consistent. Engineers can add color and saturation using their preamps instead of worrying whether the device will affect the low-frequency response of the microphone.
All AEA passive mics share the same Cinemag transformer used in our flagship R44, a passive replica of the RCA 44BX. This transformer was modeled after the classic sound of the original RCA transformer from the 1930s.
All of our active mics use a German-made Lehle transformer to give them an extra 12dB of output. This 12dB of extra gain is helpful in avoiding noise issues when using a lower gain preamp.
To clarify, this extra 12dB of output comes from the Lehle transformer itself, not from the phantom-powered electronics. We don’t want to muck up the sound of the mic by adding electronics that color it in a negative way. AEA’s active electronics are extremely transparent because of their JFET technology and do not impart any additional character to the sound.
Passive vs. Active Strategies
Passive ribbon mics can be used with a variety of preamps to experiment with the overall frequency response and sonic character of the audio. Some engineers like to use the preamp as an effect because it can drastically change the character of the mic.
We give you a choice of ribbon microphone technology to construct and shape a unique sound for your music. Though passive, active, output level and impedance are all technical issues, they also have a direct effect on artistic decisions.
Though we’ve outlined the technical “rules” in this article, we encourage artists to break them. With an understanding of how ribbon microphone technology works, engineers and musicians can then begin to seek the subtle differences that define their artistry.