New Gear Review: AEA RPQ2 Dual Ribbon Preamp
This flexible, two-channel mic preamp/EQ is geared towards use with ribbon mics, however its functionality extends far beyond.
Wes Dooley, and his company, AEA, have a long history of working with ribbon microphones.
When General Electric purchased RCA in 1976 and closed its microphone division, Dooley began servicing those iconic mics. His faithful reproduction of the original RCA 44 (as well as the KU4, a remake of the rare hypercardioid RCA KU3A) has been lauded by the engineers who built the original. And his work on new ribbon designs has helped to bring about the ribbon microphone popularity resurgence of recent years.
In addition to making some phenomenal microphones, Wes and his company also manufacture a couple of different unique preamplifier designs. The RPQ2 is an updated version of the original RPQ microphone preamp and EQ and, given AEA’s impressive pedigree, I was excited to put it to use in the studio.
Features
Priced at $1,665, this two-channel pre/DI with a low cut filter and high frequency EQ band is tailored towards getting the most out of ribbon microphones, taking both their benefits and shortcomings into account. It also works well with moving coil mics, and can be just as easily used with condensers.
Based off a transformerless JFET amplifier circuit, the RPQ2 offers up to 81dB of gain. The stated specs on the RPQ2 are impressive. The preamp sports an unweighted noise figure of less than 3dB, and a frequency response that is only -3dB from 1Hz to 100kHz. Distortion is rated at .02% at 1kHz.
Basic front panel buttons offer a mic/line input switch (more on that later), plus phantom power and a polarity reversal. The first stage of gain is controlled by a stepped switch, offering between +13dB and +62dB of level before the EQ section, with a continuously variable output level trim offering +19dB/-60dB of control, post-equalizer.
As far as visual feedback, the signal level indicators show green (-20dBu to show signal present), yellow (0dBu), and red (+24dBu to indicate approaching overload). The max output level, according to the specs, is +28dBu. In addition, a Hi-Z 1/4” direct input connection, DI selector switch, and power button are all accessible on the front panel as well.
The EQ section contains a low frequency shelving cut of -20dB, with a selectable frequency range of 22Hz-515Hz, and a high frequency EQ boost of up to +20dB of gain, with a range of 2.5kHz-30kHz. The high band is bell-shaped, but very wide. Both the low cut and high boost circuits contain bypass controls, though true bypass only exists on the high boost band.
The RPQ2’s Rear panel connections offer a unique twist as well: Standard XLR input and output jacks are available for microphone in/line out function, like most mic preamps. However, there is also a set of 1/4” TRS jacks that offer some unique capabilities. These jacks work as a balanced insert before the EQ section, which allows for several different workflows.
The Pre Out jack gives you an ultra-short signal output after only the initial gain stage for purity of signal or parallel processing. These jacks can also be used to insert any other gear (such as dynamics processors) into the signal path before the EQ. Lastly, the Line In jack allows the RPQ2 to function as an EQ only. You can actually access the mic pre and EQ separately, which neatly expands the capabilities of the unit.
The RPQ2 features pre-EQ, balanced inserts on each channel, opening a world of possibilities for use in a variety of applications.
A quick note of importance here regarding impedance and the valuable role it plays with matching mic to preamp, especially pertaining to dynamic microphones—both ribbons and moving coils.
There are two key interactive specs that matter here: Output impedance of the microphone, and input impedance of the preamplifier. A microphone and the preamp it is patched into form an interactive circuit. Generally speaking, the best practice is to have the input impedance of the preamp be at least five times greater than the output impedance of the microphone. (Some sources claim at least ten times is ideal.) This means that if a mic has an output impedance of 200 Ohms, the preamp should be rated to have an input impedance of at least 1,000 Ohms.
Too low of an input impedance can force the preceding piece of gear to work harder, and can result in distortion, noise, loss at high and low frequency extremes leading to you signal sounding damped, or dull. You might even experience lowered SPL handling capabilities. Additionally, the output impedance of a mic rises towards low frequencies—especially on ribbons.
Practically, this is usually not a problem, as most mic preamplifiers are designed with this in mind. For example, the venerable AMS Neve 1073 has an input impedance of 1200 Ohms. But this is not always sufficient. The output impedance of the Royer R-121 for instance, is rated at 300 Ohms, and recommended load impedance is greater than 1500 Ohms. The 1073 is an amazing sounding preamp and I mean to take nothing away from it. In certain cases however, it may not be the best pre for the job at hand. Having a higher rated input impedance can improve the fidelity of the mic itself, and the RPQ2 has a microphone input impedance of 63k Ohms (which switches to 10k Ohms when phantom power is engaged).
Some claim that none of the above techno-babble matters. I put the RPQ2 to work to find out.
In Use
AEA was nice enough to also send me some ribbon mics to try out with the RPQ2. So, armed with their R88 stereo passive long ribbon microphone, and their N22 active ribbon mic, I set about getting some sounds.
In the first test, I used the R88 as a stereo drum overhead. Out of the gate, it was one of my favorite overhead sounds ever: Smooth and natural with a fantastic 3-D depth and transient response. I used the onboard Curve EQ boost to add a bit of air. The top end was clear and bright, and there was nothing tizzy about the sound at all…better than I expected from a ribbon.
The next duty was as a room mic in a room that I don’t particularly like, but sometimes have to use anyway. Again the RPQ2/R88 combo delivered big time. It produced fantastic imaging and a balanced, usable sound that responded equally well to onboard EQ as well as plugin equalizers during mixdown.
At my home studio, I used the RPQ2 and performed some tests using the N22, the R88, and a very old SM58 to track voiceovers, hand claps, shakers, and acoustic guitar.
I already knew the N22 was a great mic, and it had sounded especially wonderful on lead guitars and vocals in another session, but with the RPQ2, it really shined. I noticed this effect with every ribbon or moving coil microphone I tried. My voice sounded big and full, and I was able to get in very close and then tame the proximity effect (which is especially monstrous on the R88) down to a usable amount. Most ribbons have a very strong proximity effect, but the low shelf EQ made tuning the bottom end of any signal very easy. This was killer on very close-mic’ed vocals and guitar as well.
On the percussion and acoustic guitar, the transient response was among the best I’ve heard. This preamp helped elevate the standard 58 into something very usable in realms where I never would have considered it before. Additionally, there was easily enough gain to get low level signals while keeping the noise down.
The final test was trying out the Hi-Z input. Wanting to hear just how open and clear this preamp is, I plugged in an older bass with flatwound strings. Again, I was stuck by the clean and smooth top end. There was more bite and edge than I normally get off of the flats, and I liked the versatility that added. Just the DI by itself offered a balanced bass tone.
We experimented with the low shelf and high band EQs, and were able to remove some mud and add just the right amount of sparkle, which never became harsh.
The output level control that is post-EQ allowed us to boost as much as we needed and still rein the signal back down to a usable level. I can easily see how pairing this pre with some very old and dark ribbons can instantly make them usable for recording modern sounding music.
The high band was especially flexible, and we were able to bring far away tracks forward and add presence, or just add some subtle air wherever it might be needed. I even applied some post-production processing and am happy to report that these tracks took to additional EQ without ever getting grainy or gritty. Smooth sailing all the way around.
To Be Critical
As great as the RPQ2 performed, I found the paint on the faceplate to be confusing, and the overall design is not my favorite. For example, there are eight hash marks on the output gain knob past 0dB. The extra output gain available is +19dB. Mathematically and logistically, this makes no sense.
Additionally, I felt the movement of the knobs and buttons was not up to par with the sound quality of the unit. The overall user experience feels imprecise (although in practice the gear tracks very well). I experienced no breakage or issues, but heft and feel are important. I want to be clear though… these are all very minor complaints.
Summing it Up
As with all things, it’s important to choose the right tool for the job at hand. If you are after the creamy, midrange thickness that comes from really pushing transformers or tubes, the RPQ2 is not the preamp to grab. For loud, distorted saturation, look elsewhere. However, if you want to hear the fingernails on a delicate acoustic guitar, or percussion that really pops out, this preamp will serve you fantastically.
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