By Roger Nichols
The more you know about AC power, the better you will be able to cope with
AC problems as they occur. The easiest problem to control is the most objectionable
in the studio: ground noise. That's the point of this review. But before
settling in to read this review, do yourself and your studio a favor and
read my article "Power Management in the Studio" located somewhere
else in this issue (you can find it if you listen really carefully for the
clean sound...). It will help to explain why this review is here and why
this system is important.
There is not much you can review about the Equi=Tech Symmetrical Power System,
because there are no knobs, no meters, no adjustments of any kind. There
is only a power switch on the front and some AC receptacles with circuit
breakers on the back. The "guts" of the system is the specially
wound center tapped toroidal transformer that takes the unbalanced power
in and delivers balanced, 60 volt-to-ground power on the output.
To install the Equi=Tech Symmetrical Power System, all you have to do is
plug it in to an AC supply, throw away all of your ground lifting plugs
and plug all of your equipment in to the receptacles in the back, and turn
the front panel power switch on. That's it. Nothing will hum, nothing will
buzz, your studio will be the quietest thing you have ever heard, or not
heard in this case.
I have been using an Equi=Tech unit for about nine months. I have had fewer
digital errors when transferring signals between equipment. AES and S/PDIF
work as well as optical now. On the analog side, my transformerless tube
mic pre amp is 15 dB quieter. As an average, all analog equipment has measured
12 to 16 dB quieter just because of the balanced power.
A few weeks ago I had to record some piano and vocal overdubs at a studio
that does not use balanced power. On the piano I was using a pair of Sony
C800-G (the ones with the heat sink) microphones. On the vocal I was using
a prototype of the new Audio-Technica 4060 tube mic. Under normal circumstances,
the electrical noise floor at the studio left something to be desired. I
was about to change all of that.
I brought an Equi=Tech Symmetrical Power System with me to the session.
I fed the outputs of the microphones into the mic inputs of the Apogee AD-1000
converter. The microphone power supplies and the Apogees were powered by
the Equi=Tech. I then fed the digital signal from the Apogees directly to
the digital input of the Sony 48 track digital machine. Since the signal
was digital before it got to the studio's power environment, the signals
stayed Equi=Tech quiet.
The difference was amazing! I could finally hear what fantastic microphones
sound like. When referenced to a quiet ground, even the low level noise
that you usually associate with tube microphones was gone. I couldn't even
tell if the mics were on until someone walked into the overdub room. This
is the way recording was meant to be.
I expect every studio I work in from now on to be powered by balanced AC.
The units come in various power output configurations and multiple units
can be run in parallel. This is by far the least expensive way to rocket
your studio into the digital quiet age. With the inclusion of balanced power
60 V to ground in the 1996 Electrical Codes for audio and post production
facilities, there is no longer any excuse.
No matter what I plugged in, no matter how I interconnected the audio, I
could not force a ground related hum or buzz. This was always a problem
in the past when someone wanted to bring in their own piece of audio gear
to patch into the chain. Now I encourage it.
Equi=Tech Corporation, P.O. Box 249, Selma, OR 97538; tel.: 503-597-4448.
PRICE: Equi=Tech presently offers many models in each of three basic categories
Rack ($1,399-2,779); Wall ($3,959-5,359); and Portable ($3,859-4,859). Models
within each category furnish varying amp sizes, capacity, input lines and
options. Call the manufacturer for exact system requirements and costs as
well as on questions regarding custom systems.