IT-20 II - Owner’s Manual
F e at u r e s
• Ultra-low noise balanced isolation transformer provides over 80 dB of common noise reduction form
20Hz - 20kHz, assuring the lowest noise floor possible for today’s sensitive recording equipment
• Toroidal transformer assures contained magnetic field, allowing any component to operate in close
proximity without inducing noise
• GFCI protected outlets with Ground Lift switch to eliminate AC hum and ground induced noise
• Furman’s Linear Filtering Technology (LiFT) provides well over 40 dB of differential mode noise
reduction from 100kHz-1Ghz for unequalled audio clarity
• Series Multi-Stage Protection Plus (SMP+) for virtually maintenance-free protection from surges and
spikes. No sacrificed parts, no service calls, no downtime!
• Automatic Extreme Voltage Shutdown (E.V.S.) will power down equipment during a prolonged and /
or extreme over-voltage situation
• 20 amp capacity with 12 ultra-low resistance isolated-ground Hubbel AC outlets, plus two front panel
convenience outlets
IT-20 II - Owner’s Manual
Thank you for your purchase of a Furman IT20 II 20 amp Balanced Power Conditioner,
and congratulations on your choice. This
specially wound and shielded toroidal isolation
transformer is designed specifically to reduce
hum pickup by sensitive equipment when ultralow-noise is a must.
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, the 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.
I n s ta l l at i o n
The power source to which the IT-20 II is
connected must be adequate for use at 20 amps.
We recommend a 30 amp circuit, wired with
10 gauge wiring, if continuous operation near
20 amps is anticipated. A dedicated (nothing
else connected) 20 amp circuit is the minimum
acceptable to comply with NEC requirements.
Consult a qualified electrician if in doubt. The IT20 II is designed for mounting in a standard 19
inch equipment rack. Because of its weight, the
best position for it is the bottom slot of the rack.
Its toroidal transformer minimizes magnetic
leakage, but nevertheless, due to its high
capacity, it will radiate an appreciable magnetic
field. Therefore, we recommend that it not be
positioned adjacent to sensitive, low level signal
processors, especially mic preamps, mixers,
tape recorders, etc. Power amps may be more
suitable “rack neighbors.”
The maximum benefit is derived from balanced
power when it powers ALL equipment in an
installation. Therefore, try to position the IT-20
II in a central location so its power can be easily
distributed everywhere it’s needed. If the total
power consumption of all equipment exceeds 20
amps at 120 volts, delete high level or mechanical
devices first (such as power amps, motors). If
possible, physically isolate any equipment that
has to be powered with conventional power
through a different circuit, and route their AC
cords away from all other cabling. The balanced
power produced by the IT-20 II is restricted to
use with electronic equipment only. Balanced
power may not be used for lighting equipment,
and access must be limited to use by qualified
personnel only.
If you are installing the IT-20 II in a rack that
has rear as well as front mounting rails, you may
wish to order adjustable rear rack ears from
Furman. These allow the IT-20 II to be securely
attached in both the front and back. Order model
IT-20 II - Owner’s Manual
O p e r at i o n
Circuit Breaker/Switch
The IT-20 II has a large black switch on the front
panel that is both a precision circuit breaker and
an on-off switch. If circuit breaker is tripped,
manually reset the unit by turning it off and then
back on, to restore power.
Ground Fault Interrupter (GFCI):
The GFCI on the IT-20 II’s front panel is a special
kind of circuit breaker that detects an imbalance
in the current flowing in the two hot legs. The
“missing” current is presumed to be flowing
through the ground conductor (the round pin on
an AC outlet).
Ground current often indicates a dangerous
partial or full short circuit. If an imbalance is
detected, the GFCI trips and cuts off power not
only to itself, but to all the IT-20 II’s outlets. If
this occurs, the button on the GFCI marked
“R” (Reset) will pop out. To restore operation,
correct the fault and push the button in. You may
test the proper operation of the GFCI at any
time by simulating a ground fault by pushing the
button marked “T” (Test). If the GFC1 is working
properly, this will cause the “R” button to pop
out and cut off power. You can restore operation
after a test by pushing the “R” button in.
Ground Lift Switch
Ground loops are fairly common in many
installations because AC cords with safety
ground are rarely connected to a single lowresistance buss bar. When there is a significant
difference in voltage between a source
component’s neutral and ground and a load
component’s neutral and ground, the buzz and
hum associated with this type of ground current
noise (or loop) may take place. Additionally,
many AC noise contaminants may be present on
the AC ground wire. For these reasons Furman’s
IT-20 II contains a Ground Lift Switch.
This switch floats the output ground, eliminating
ground noise and also, in many instances, the
hum and buzz associated with ground loops.
The IT-20 II’s GFCI protection circuit assures
that even when utilizing the power conditioner
in this mode, operation is safe and secure.
In fact, even if a connected component has
a catastrophic failure, less than 5 milliamps
current imbalance from line to ground or neutral
to ground will instantly disconnect the voltage
output from the IT-20 II. This is far safer than
any conventional 120 VAC outlet, and it has
numerous noise reducing advantages.
However, ground wiring in any studio, broadcast
or club environment can be complex. Because
all 14 outlets of the IT-20 II are in parallel,
it is still possible to have a ground loop if the
two offending products are simultaneously
connected to a single IT-20 II. Use of multiple
IT-20 II’s may be necessary in extreme cases.
Also, for studio and broadcast use, separating
all digital processing products from all analog
devices is highly recommended and can be
accomplished by using two IT-20 II’s.
In the end, it is best to experiment with this switch.
Whichever position yields the least noise or
clearest audio / video recording or reproduction
is the position that should be utilized.
B a l a n c e d AC P o w e r
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
IT-20 II - Owner’s Manual
practices established over a century ago, when
electric power use was limited to lighting and
motors, long before any AC noise sensitive
applications existed. The emphasis then was on
convenience (from the power utilities’ 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 “hot” (120V) and “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. 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 “differential
mode,” is responsible for well over half 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.
Linear Filtering Technology (LiFT)
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
re-boot digital pre-sets, or destroyed digital
converters are frequently caused by excessive
voltage spikes and AC noise contaminating the
equipment ground. Furman’s LiFT takes another
approach, ensuring optimal performance through
linear filtering and no leakage to ground.
Series Multi-Stage Protection Plus
Traditional surge suppression relies on circuits
that “sacrifice” themselves when exposed to
multiple transient voltage spikes, requiring
the dismantling of your system and repair of
your surge suppressor. With Furman’s SMP+,
however, damaging transient voltages are
safely absorbed, clamped and dissipated. No
sacrificed parts, no service calls, no downtime.
Also unique to Furman’s SMP+ is its unparalleled
clamping voltage. While other designs offer
clamping voltages that are well above 300Vpk,
Furman’s SMP+ clamps at 188Vpk, 133 VAC
RMS, even when tested with multiple 6000Vpk,
3000 amp surges! This unprecedented level of
IT-20 II - Owner’s Manual
protection is only available with Furman’s SMP+
• The power supply cord or plug has been
frayed or cut
• Objects have fallen or liquid has spilled into
the unit
Extreme Votlage Shutdown (E.V.S.)
When voltage rises to extreme levels because
of a lost neutral line or an accidental connection
to 208 or 240 VAC, Furman’s Extreme Voltage
Shutdown kicks in, automatically powering down
all equipment quickly and safely to prevent
damage from occurring. An indicator LED will
then illuminate, alerting you to the situation until
the over voltage condition is corrected by turning
the unit off and then back on.
Digital Voltmeter:
This LED digital voltmeter is an accurate, selfchecking AC voltmeter that continually measures
the IT-20 II’s input AC voltage.
S a f e t y I n f o r m at i o n
and Warnings
Please read and observe all of the safety and
operating instructions before the IT-20 II is
operated. Retain these instructions for future
• Do not disassemble or modify in any way.
No user-serviceable parts inside
• Keep away from moisture and avoid
excessive humidity
• Do not allow liquids or foreign objects to
enter the unit. Household lighting equipment
may not be connected to the IT-20 II because
its sockets are not designed for use with
symmetrical power and may present a shock
hazard. We recommend that only audio,
video and computer processing equipment
be connected to the IT-20 II
The IT-20 II should be serviced by qualified
service personnel when:
• The IT-20 II has been exposed to rain or
other moisture
• The IT-20 II does not appear to operate
normally, or exhibits a marked change in
• The IT-20 II has been dropped, or the
enclosure damaged
The IT-20 II requires that a safety ground be
present for proper operation. Any attempt to
operate the IT-20 II without a safety ground
is considered improper operation and will
invalidate the warranty.
Power Source
The power source to which the IT-20 II is
connected should be adequate for use at 7
amps. Typical household outlets will have a
current capacity of at least 10 - 15 amps.
Furman Sound, LLC., having its principal place
of business at 1690 Corporate Circle, Petaluma,
CA 94954 (“Manufacturer”) warrants its IT-20 II
(the “Product”) as follows:
Manufacturer warrants to the original Purchaser
of the Product that the Product sold hereunder
will be free from defects in material and
workmanship for a period of three years from the
date of purchase. The Purchaser of the product
is allowed fifteen days from the date of purchase
to complete warranty registration by mail or online at the Furman website. If the Product does
not conform to this Limited Warranty during the
warranty period (as herein above specified),
Purchaser shall notify Manufacturer in writing of
IT-20 II - Owner’s Manual
the claimed defects. If the defects are of such
type and nature as to be covered by this warranty,
Manufacturer shall authorize Purchaser to
return the Product to the Furman factory or to
an authorized Furman repair location. Warranty
claims should be accompanied by a copy of the
original purchase invoice showing the purchase
date; this is not necessary if the Warranty
Registration was completed either via the mailed
in warranty card or on-line website registration.
Shipping charges to the Furman factory or to
an authorized repair location must be prepaid
by the Purchaser of the product. Manufacturer
shall, at its own expense, furnish a replacement
Product or, at Manufacturer’s option, repair the
defective Product. Return shipping charges back
to Purchaser will be paid by Manufacturer.
PARTICULAR PURPOSE. Manufacturer does
not warrant against damages or defects arising
out of improper or abnormal use of handling of
the Product; against defects or damages arising
from improper installation, against defects in
products or components not manufactured by
Manufacturer, or against damages resulting
from such non-Manufacturer made products or
components. This warranty shall be cancelable
by Manufacturer at its sole discretion if the
product is modified in any way without written
authorization from Furman Sound. This
warranty also does not apply to Products upon
which repairs have been affected or attempted
by persons other than pursuant to written
authorization by Manufacturer.
with respect to the Products or any part
thereof, whether based on contract, tort, strict
liability or otherwise. Under no circumstances,
whether based on this Limited Warranty or
otherwise, shall Manufacturer be liable for
incidental, special, or consequential damages.
Manufacturer’s employees or representatives’
not be relied upon by Purchaser, and are not
a part of the contract for sale or this limited
warranty. This Limited Warranty states the
entire obligation of Manufacturer with respect to
the Product. If any part of this Limited Warranty
is determined to be void or illegal, the remainder
shall remain in full force and effect.
S e r vi c e
Before returning any equipment for repair,
please be sure that it is adequately packed and
cushioned against damage in shipment, and
that it is insured. We suggest that you save the
original packaging and use it to ship the product
for servicing. Also, please enclose a note giving
your name, address, phone number and a
description of the problem.
NOTE: All equipment being returned for repair
must have a Return Authorization (R/A) number.
To get an R/A number, please call the Furman
Service Department at 707.763.1010 extensions
113 and 133. Please display your R/A number
prominently on the front of all packages.
and exclusive obligation of Manufacturer shall
be to repair or replace the defective Product in
the manner and for the period provided above.
Manufacturer shall not have any other obligation
AC Current Output:
20 Amps (2400 watts at 60/120V)
Shutdown Voltage:
At 135-140 VAC
Heavy duty power cord with 20A three-pronged plug
12 rear (isolated), 2 front (GFCI) each rated at 20 amps
Spike Protection Modes:
Line to neutral, zero ground leakage
Spike Clamping Voltage:
188 Vpk @ 3,000 amps, 133 VAC RMS
(Tested to UL-1449 6,000 Vpk @ 3,000 amps)
Response Time:
1 nanosecond
Maximum Surge Current:
6,500 amps
Differential Noise Attenuation:
10dB @ 10kHz
40 dB @ 100 kHz
100 dB @ 10 MHz
Common Noise Attenuation:
Greater than 80 dB @ 20Hz to 20 KHz
Greater than 40 dB @ 20Khz to MHz
Linear attenuation curve from 0.05-100 ohms line impedance
Turns Ratio:
1:1, windings separated with Faraday Shield
Transformer Regulation:
3% at full load
Power Consumption:
12 watts for display and control circuits
Voltmeter Accuracy:
± 1V
19” W x 5.25” H x 17” D, 80 lbs.
Furman Sound, LLC
1690 Corporate Circle.
Petaluma, California 94954-6919 USA
Phone: 707-763-1010
Fax: 707-763-1310