The RPQ500 has a clear front panel layout.
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AEA RPQ500
By Paul Vnuk Jr.
Date: August 2012
Wes Dooley's Audio Engineering Associates (AEA) is known for its line of high-end
ribbon microphones as well as being one of the world's foremost restoration specialists
of vintage RCA ribbon models. AEA also manufactures a line of high-end microphone
preamps that, as you can guess, are designed to literally get the most out of your ribbon
microphones.
Today we are looking at AEA's newest mic pre model, the RPQ 500, which is a few
evolutionary steps up from AEA's TRP (short for The Ribbon Pre) released in 2006.
Reviewer Scott Dorsey gave us the lowdown on the TRP in our March issue of that year
and commented on the clarity it brought out in a ribbon microphone.
Two years after its release came the RPQ, and while its raison d'etre was still primarily
the world of ribbon microphones, there were other improvements as well that went
beyond ribbons: optional phantom power, a sweepable high-band eq called the Curve
Shaper, and a variable low-frequency filter.
The newest member of the AEA family, the RPQ 500, is a single channel from the 2channel RPQ, designed for use in an API 500-Series style enclosure (For this review, I
used the Radial Workhorse enclosure, reviewed in our October 2011 issue). All of the
RPQ’s features are included as well as a new variation or two.
Style, build, and functions
The RPQ 500 is a single-slot module that is fully enclosed in a zinc-plated steel chassis
with a 0.125" black tinted anodized aluminum front plate. It uses the same full-sized
silver knurled knobs as its 19" rack mount sibling -- it looks quite imposing sitting next
to many other 500 series devices with their tightly spaced miniature controls and pots.
As with the RPQ, signal flow starts with a 12-stepped Grayhill pot that goes from +7 dB
up to +56 dB of preamp gain. This is followed by a variable output level control that
goes from minus infinity (muted) up to +19 dB. The FET output circuit also adds +6 dB
of gain, so at full throttle the RPQ 500 can give you +81 dB of clean gain -- yes, 81 dB,
you read that correctly.
In between the input and output is a Low Frequency Filter control that is fully
sweepable from 18 Hz to 360 Hz and drops the selected frequency down -20 dB,
shelving, with 6 dB/octave slope. Next is the Curve Shaper, a sort of high-band shelving
eq. One control adjusts the circuit's gain from 0 dB up to +20 dB, while the other selects
the frequency from 2.1 kHz up to 26 kHz. Both the Curve Shaper and the Low Freq
Filter include bypass buttons so they can be taken in and out of the signal path.
Additionally the RPQ 500 has a phase button, a phantom power button, and a 3-stage
signal level/clip LED meter.
About the 500 Series' use of phantom power: On the original RPQ, there were two sets
of XLR inputs, one for use with ribbons and devoid of voltage, and a second standard
input with phantom power for use with typical condenser microphones. On the 500Series version there is of course only one XLR input and its phantom power is
switchable in and out, so the same care needs to be taken as when using any mic pre
with a ribbon microphone.
The last feature is also specific to the RPQ 500, and that is a Mic/Line switch that
changes the input from mic level to a line-level signal. This takes the input stage and
phantom power out of the path and allows you use the eq section alone during
mixdown, on any source.
Sound and use
The RPQ 500 falls squarely in the Millennia Media, John Hardy and Grace Designs
camp and holds its own with them all. Of those three I found it sonically closest to the
John Hardy. It is clean and clear and simply stays out of the way and imposes no tone of
its own to the mic.
Where it differs from the pack is more in function than sound, as its impedance load is
specifically tailored to ribbon mics, and, again, it offers +81 dB of gain, more than the
competition’s +65 to +70 dB of gain.
It’s easy to get a great level when tracking loud sources like drums, guitar cabinets and
brass sections with a ribbon microphone, but on delicate acoustic guitar, soft crooning
vocals, violins and voiceover work, I often end up pushing my mic pres to their limits,
thus boosting their noise floor to the point where it becomes a detriment to the intimate
recording I was attempting in the first place. With the RPQ 500 I achieved the single
quietest signal with the lowest noise floor I have ever experienced with a ribbon
microphone, and it plays no favorites in that category, from a Royer R-121 to AEA's
own R84 with a few Chinese-made suspects in between.
On condensers like my Neumann KM 84s and my Brauner Phantom and even most
modern tube microphones, gain typically is not an issue and here is where the RPQ 500
treads similar ground to my Millennia Media HV-3D. However, my biggest surprise
came when pairing the RPQ 500 with a moving-coil/dynamic Shure SM7B. I love this
microphone and what it does for vocals and voiceovers, but too often I have the same
experience as when I use low-output ribbons -- too much noise floor. The RPQ 500
gave me the most clear and clean and musical sound I have ever heard from my SM7B!
Curving the tone
While functionally simple, the Low Frequency Filter is not a typical highpass filter. Its
cut is nowhere near as steep, so it’s more of a low-end 'lessener' than 'eliminator', but in
most of my tests that was fine as it tucks the low end back into the mix rather than
eliminates it.
The Curve Shaper also takes some practice to get the hang of, as the throw of both the
boost and the frequency range are pretty extreme. Since adding just 2 dB of eq can
change a sound's placement in a mix substantially, imagine what can happen with +20
dB. If your mic has any noise floor at all you can easily push it over the top, so be
careful. Also this is one of those eqs with an "air" band, and once you move beyond
about 18 kHz, especially up into the mid-20s, what is added is more perceived than
directly heard.
Once you master these two features you can nicely tailor your ribbon mic from a dark
traditional tone to a sound that is more condenser-like and modern, yet still smooth.
Lovely!
Conclusions
It’s easy to pass by a mic pre like this if you don't own or do much with ribbon mics, but
the RPQ 500 is so much more than a one-trick or one-mic pony. It holds its own
comfortably with all the members of the "straight wire with gain" family and has some
nice tricks up its sleeve that set it apart as well. Of course if you are a ribbon
connoisseur and/or a 500-Series rack owner, then you really need to demo one of these
preamps as soon as you can... it will change your expectations about what you can do
with even the lowest-output mics.