|Designed for the most critical, ultra-low noise installations, the
IT-20 II can supply 20 amps of Balanced AC power for recording studios,
broadcast stations, or video production facilities. To understand the
incredible need for clean noise-free AC power, it's important to note
that today's sophisticated studio equipment features tremendous dynamic
range. Most of the signal content that defines high resolution such as
harmonics, instrument timbre, high frequency extension, spatial cues,
and fast transient attacks in audio are inherently low in signal level.
Further, when AC noise is induced into audio processors, pre-amplifiers,
microphones, powered monitors, computers, and mixing consoles these all
important low level signals are distorted or masked. Once signals are
masked there is no way to retrieve the lost content. Advanced AC
filtering is critical when audio or video resolution is at stake. With
Furman's IT-20 II, for the first time you will hear audio content and
see video images as they were meant to be - pristine. Add to this our
SMP non-sacrificial surge suppression, E.V.S. protection, Linear
Filtering Technology (LiFT), and laboratory grade digital voltmeter and
you will be assured that AC noise and surges are a thing of the past.
Balanced AC Power
In much the same way that balanced audio lines can reduce the pickup of
hum and other types of electromagnetic interference (EMI), the use of
balanced AC power lines in sensitive audio, video, or computer
installations can make an enormous difference in system noise and signal
integrity. But power distribution in North America, unfortunately, is
not balanced. The distribution standards currently in use were derived
from practices established over a century ago, when electric power use
was limited to lighting and motors ﾗlong before any AC noise sensitive
applications existed. The emphasis then was on convenience (from the
power utilities ﾗ standpoint) and safety, but not noise cancellation.
The result was a three-wire distribution scheme in which 120V branch
circuits have a hot wire and a neutral wire, with the neutral tied to a
third wire connected for safety to an earth ground. The third wire does
not carry any current unless there is a fault. This unbalanced scheme
can create hum in audio circuits for two main reasons. First, the
current flowing in the hot wire induces hum in any other nearby wires,
which may carry vulnerable low-level audio or video signals. Second,
because the impedance of chassis and cable shielding to ground is always
greater than zero ohms, ground current flowing from power supply
capacitors and from EMI pickup causes a voltage drop at 60Hz and its
harmonics. This low level noise becomes part of the audio signals.
With a center-tapped isolation transformer, the AC power feeding a
studio can be balanced at its source. The current-carrying wires then
are no longer ﾓhot" (120V) and ﾓneutral" (0V), but two 60V lines of
opposite polarity (referenced to ground connected to the center tap),
whose difference is 120V. This type of power, when run around a room,
does not induce hum into nearby audio wiring, because the two conductors
induce equal and opposite voltages that cancel each other out.
Similarly, ground currents are all but eliminated by the same
common-mode cancellation effect. No longer is it necessary to adopt
cumbersome and expensive star-ground systems or use massive bus bars or
heavy ground rods. Further, with features such as our center tap ground
lift, ground induced noise may be reduced even further.
Of course Balanced AC Power is only the beginning of a system free of
AC noise. Asymmetrical noise or what is called ﾓdifferential mode" is
responsible for well over half of the noise present in today's AC lines.
For this reason we employ our exclusive Linear Filtering Technology
(LiFT). This assures that your audio, video, or computer signals are as
pure and uncorrupted as possible.
SMP+ (Series Multi-Stage Protection Plus)
Furmanﾒs SMP+ surge suppression virtually eliminates service calls.
Traditional surge suppression circuits sacrifice themselves when exposed
to multiple transient voltage spikes, requiring the dismantling of your
system, and repair of your surge suppressor. Not so with SMP+. With
Furmanﾒs SMP+, damaging transient voltages are safely absorbed, clamped
and dissipated - no sacrificed parts, no service calls, no down time.
Unique to Furmanﾒs SMP+ is its unparalleled clamping voltage, even
when tested beyond the grueling specifications of - USA/CIDAﾒs A-1-1
test. While other designs offer clamping voltages that are well above
300VAC peak (far beyond long accepted professional standards), Furmanﾒs
SMP+ clamps at 188VAC peak, 133 VAC RMS even when tested with multiple
6000VAC - 3000 Amp surges! This unprecedented level of protection is
only available with Furmanﾒs SMP+ technology.
LiFT (Linear Filtering Technology)
Unfortunately, traditional AC filter/conditioners have been designed for
unrealistic laboratory conditions. Prior technologies could actually
harm audio and video performance more than they help, due to the
resonant peaking of their antiquated, non-linear designs. Under certain
conditions, these designs can actually add more than 10 dB of noise to
the incoming AC line! Worse still, lost digital data, the need to reboot
digital presets, or destroyed digital converters are frequently caused
by excessive voltage spikes and AC noise contaminating the equipment
ground. Furmanﾒs SMP+ with LiFT takes another approach, ensuring optimal
performance through linear filtering and no leakage to ground.
E.V.S. (Extreme Voltage Shutdown)
Furmanﾒs trusted overvoltage circuitry protects against all too frequent
accidental connections to 208 or 240VAC by shutting off the incoming
power until the overvoltage condition is corrected.
Optional RRM-2 Rear Rack Mount Ears (sold
Adjustable depth rack mount ears for the IT-20 II. Adjustment depth is
17" to 18.25" from inside front panel.