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Dual-channel Microphone Preamplifiers By Hugh Robjohns
Published March 2024


Designed to get the very best out of passive ribbon mics, AEA’s preamps offer way more gain than most. But they’re not just for ribbons...

AEA's original TRP, which I reviewed in SOS April 2007 (, was a compact (half‑rack width), no‑frills, two‑channel preamp with an external power supply. Designed by Fred Forsell, it was entirely dedicated to getting the best possible signal from vintage ribbon mics, which are notorious for their low sensitivity. Consequently, it didn’t provide phantom power and featured a DC‑coupled input with an exceptionally high input impedance (18kΩ) to minimise the electrical load on ribbon mic motors. Despite the absence of (free‑gain) input and output transformers, the active circuitry provided a whopping 83dB of gain using a Grayhill rotary switch (6‑63 dB in 12 steps) plus a continuous output level control offering up to 20dB of extra gain (as well as fading down to silence).

Other features included on each channel were a second‑order (12dB/oct) 100Hz high‑pass filter, polarity inversion and simple traffic‑light metering. Internally, the circuitry was based around a combination of discrete JFET gain stages at the front end and op‑amps for the filtering and output sections, fabricated using mostly SMD (surface mount) technology, with sealed relays for switching functions. Despite the enormous gain on offer, the design maintained a huge bandwidth (‑3dB at 6Hz and 300kHz) for a phenomenal transient response, with a generous headroom margin (+28dBu), and incredibly low noise (EIN figure of ‑130dBu A‑wtd).

So impressed was I with the TRP’s sublimely neutral, yet musical sound character, unusually high‑gain, and astonishingly quiet noise‑floor that I bought the review model without hesitation. I’ve used it regularly ever since, both with my best low‑output moving‑coil mics (Beyer M201 and AKG D224E) as well as all manner of vintage and modern mono and stereo passive ribbons. It never disappoints, and always extracts the very best that any of these dynamic mics can deliver.

Of course, being the annoyingly picky soul I am, I identified a few ‘cons’ of the original TRP. The lack a front‑panel power switch was a mild frustration, as was the seven‑pin DIN power socket, and the high‑pass filter design turned over from too high a frequency to be useful at removing rumble, yet was too steep to properly correct for proximity effects. Not that any of these minor grumbles really bothered me in practice, but I’ve taken a keen interest in the development of this excellent design since then. We’re now on version three of the TRP, which is reviewed here, and there have been a few related products too, not least the RPQ and its own revisions.


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