Recording - February 2016 - 80

B Y M I K E M E T L AY

Mark Pirro of Placid Audio has a mission-to
build microphones whose character is unmistakable and unique. He's not about "flexible Swiss
Army mic that sounds clear and clean on multiple sources".... he's about "Oh my gosh this
mic doesn't sound like anything I've ever heard
before and I love it".
Pirro's first microphone was the Copperphone
(September 2008), developed for Polyphonic
Spree bandmate Tim DeLaughter to provide a band-limited

granule element (used for intercoms in battle
tanks) is connected to a Hammond output
transformer for a balanced output that can
handle very long cable runs with ease.
The Carbonphone mic comes bundled with a
nicely-finished birch box with an LED and clickknob on the front, and Neutrik XLR in and out
plus a 9V power plug on the back. This is the
Tone Box, which isn't vital to using the Carbonphone
but greatly adds to its flexibility.

Placid Audio Carbonphone
The world's first microphone makes a fascinating comeback
"old time radio" voice effect for the Spree's live shows. It was followed
by the Copperphone Mini (reviewed July 2015), a smaller version with
a slightly different tonality. Both Copperphones received glowing
reviews for their unique character, but compared to the Carbonphone,
they're positively pedestrian....
Carbon?
Yes, carbon. Articles in this magazine usually talk about the
three types of mics-dynamic (a speaker in reverse), condenser (a
capacitor), and ribbon (a vibrating metal ribbon in a magnetic
field). Those aren't the only mic types out there; they're merely the
ones that are popular in studios today.
There are other ways of transducing sound waves into electricity,
and the carbon mic is the very first, invented by David Edward Hughes
in the early 1870s. A carbon mic consists of two discs separated by
loose-packed carbon granules. Sound waves hit one disc and make it
vibrate, causing a variable pressure on the granules, which changes
their resistance over time and creates a variable electric signal.
If you were to unscrew the mouthpiece of a pre-electronic telephone as were common around the world for most of the 20th
Century, a self-contained carbon "button" mic would fall out.
They're still in use today; they can provide a strong signal from very
low voltages, so they're handy in situations where higher voltages
are dangerous because sparks can cause explosions-think oil
refineries or coal mines. They're also very sturdy and highly resistant to sudden voltage transients, which makes them lightning-proof
(and nuclear bomb EMP-proof, if you worry about such things).
However, there's a reason they're not in common use, and never
got closer to a studio than early radio broadcasts-where they were
abandoned as soon as vacuum tube amplification made other mic
types viable. Carbon elements have a very, very restricted frequency
response-they're the reason why we think of a midrangy and distant
sound as a "telephone voice." Instant dealbreaker for most engineers... and just the sort of thing that Mark would find intriguing.
The mic and its box
The Carbonphone, like its siblings, is packaged in a polished
copper casing that's been sealed with clear lacquer to prevent
patina. It's mounted on an aircraft aluminum bracket that features
a standard 5/8" threaded mic stand socket, and uses a conventional Neutrik XLR connector. Internally, the military-grade carbon
80

RECORDING February 2016

The Tone Box is a phantom power source for the Carbonphone and
has five different filter settings built in. There are no specs on the filters;
they're meant to be listened to and selected for a particular application.
Some are thinner and more tinny, some pass more lows, and some
have interesting resonant peaks, all with very distinct character. If you
plug the Carbonphone directly into your mixer and hit it with phantom
power, it will need gain settings roughly similar to those of a dynamic
mic, and provides yet another tonality, with a hair more bottom end
than the Tone Box provides. Six sounds in one-not too shabby!
In use
The Carbonphone has to be heard to be understood. This is a deliberately "funky" sound, with sputtering, crackles, and a glorious 500 Hz
to 10 kHz frequency response. Mine had a lovely gritty timbre but was
surprisingly fussy about sibilants (easily tamed with a touch of de-esser).
I actually found it sounded a bit better after I smacked it a few times to
loosen up the carbon granules-a process recommended by Placid.
I used it live on the air for my weekly radio voiceovers and got
all kinds of comments from the audience, most of which boiled
down to "It's really weird, but I like it!". It lends a similar old-timey
character to singing, but is even more steampunk than the
Copperphones, which I didn't think was possible!
I also tested the Carbonphone on acoustic guitar, winds, and
hand percussion, and in each case it added a certain something
to the tone that really caught the ear. You wouldn't record a
whole song with it, but as an accent it's undeniably fascinating. I
also tried out the Tone Box on a couple of other mics and found it
a lot of fun for playing with tonality, lending a little of the
Carbonphone's mojo to otherwise pristine mic sounds.
So
This isn't an "I need it" mic unless you're deliberately recreating
hundred-year-old radio shows. It is, however, an "I want it" mic for
folks interested in sounds they can't get any other way. Check out
the audio samples on the Placid Audio website for yourself. I think
you'll be very impressed with what this hand-built piece of real
audio history has to offer.
All together now: "I heard you on the wireless back in '52..."
Price: $399.99 (includes Tone Box and power supply)
More from: Placid Audio, www.placidaudio.com

http://www.placidaudio.com

Table of Contents for the Digital Edition of Recording - February 2016