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Produkte > Studio Equipment > AEA > Ribbon Preamps
The Ribbon Preamplifier

- Stereo Mikrofon Vorverstärker für Bändchen-,
   dynamische um Röhren-Mikrofone
- 83dB Gain mit klarem und weichem Klang
- No Load™ DC coupled Design für erweiterten Bass
- Phase Reverse & High Pass Filter

The Original Ribbon Preamp
The TRP (The Ribbon Pre) is an  ultra high gain and high impedance, minimal-path FET microphone preamp  designed by Fred Forssell. At a time when most preamps were geared  towards the needs of condenser mics, the launch of AEA’s TRP started a new movement in preamp design that specifically addresses the needs of  ribbon mics. First, the JFET discrete front end provides 83 dB of gain.  We designed that gain as quiet as physically possible opening up new  possibilities for engineers using low sensitivity microphones. By  leaving out the phantom power blocking capacitors and by using an  external power supply, we created a minimal-path circuitry that captures  the pure tone of your passive ribbons all the way down to the lowest  bass frequencies. Secondly, the ultra high input impedance of the TRP’s  input stage avoids any preamp loading effects to ensure that you get the  all the sound your passive ribbon and moving coil microphones can  deliver. The TRP is a cost-effective, high-quality solution providing a  pure and transparent signal path for all ribbons, tube, and moving coil  microphones that do not need or do not want phantom power.

Professional Features in a Compact Package
Despite  the small half-rack footprint, the TRP packs several key features that  are critical for professional recording. The gain structure of the  2-channel (dual mono) preamp consists of an input gain control and an  output level control. The input gain is set with a high-grade twelve  position Grayhill switch. Another 21 dB of additional gain are provided  by the output stage and controlled via a continuous pot that acts as a  fader. The output fader not only allows for executing minute and  click-free gain adjustments while recording, but it also facilitates the  possibility of fade-outs and doubles as a mute function.

Professional Neutrik 3-pin XLR and ¼” TRS outputs provide simultaneous balanced and  unbalanced outputs, allowing the TRP’s signals to be sent to two devices  at the same time without the need for additional splitting. In a live recording situation, for example, the balanced outputs could feed the  live mixing console while the unbalanced TRS signal is sent to a  recorder or DAW interface.

Polarity reverse switches for ensuring  proper polarity throughout the recording chain and switchable 100 Hz, 12  dB per octave high pass filter (HPF) per channel complete the toolkit  of the TRP. Internal audio switching is handled by gold-contact relays  keeping the audio path short and simple for best sound.

The Impedance Matching Myth
Passive  microphones like ribbons and moving-coil transducers interact with the  input impedance of the preamp. If the impedance of the preamp is too  low, the microphone will have to work harder to send a signal down the  line. Additionally, the bandwidth (particularly in the low end) will be  limited.

For best voltage transfer, the impedance of the preamp  should be at least five times the microphone’s output impedance. Many  microphones have a nominal impedance of about 200 Ω, leading to the  assumption that a preamp impedance of 1.0 to 1.5K Ω should be fine.  However, passive microphones, and ribbons in particular have an output  impedance that rises towards low frequencies and can easily get as high  as 1000 Ω at resonance, resulting in a 6 dB loss at this frequency with a low impedance preamp. A preamp impedance of significantly more than the  commonly seen 1.0 to 1.5K Ω is beneficial for all passive ribbons and  moving-coil microphones.

All AEA preamps have input impedances of  at least 10K Ω for these reasons. Microphone loading because of low  impedance preamps can lead to interesting creative results, but AEA’s  NoLoadTM inputs will guarantee highest sensitivity and bandwidth in all situations.
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