Furman IT1230 User Manual

Furman Sound, Inc.
1997 South McDowell Blvd.
Petaluma, California 94954-6919 USA
Phone: [phone]
Fax: [phone]
Web: http://www.furmansound.com
E-mail: [e-mail]

Balanced AC Power Isolation Transformer, 30A

MODEL IT-1230

Owner’s Manual

Introduction

Thank you for your purchase of a Furman IT-1230 30 Amp
Balanced AC Power Isolation Transformer, and congratulations
on your choice. This specially wound and shielded toroidal
isolation transformer is designed specifically to reduce hum pickup
by sensitive equipment when ultra-low-noise is a must.

Features

● Provides precisely balanced AC power for ultra-low-noise

installations

● Typically gives a 16 dB improvement in background noise floor

in systemwide installations

● Toroidal transformer with center-tapped secondary is the most

efficient, compact design, with least magnetic field leakage

● Soft Start circuit prevents turn-on transients and high inrush

currents

● Faraday shield reduces electrostatic coupling between primary

and secondary

● Extreme Voltage Shutdown circuit protects against dangerously

high or low input voltages

● Microprocessor-controlled “smart” AC voltmeter monitors line

voltage, flashes alerts for marginal and extreme conditions

● Provides basic power conditioning functions (spike

suppression, RFI filtering)

● Ground fault interrupter (GFCI) protection

1-9843

Description

Designed for the most critical, ultra-low-noise installations,
the IT-1230 can supply 30 amps of balanced AC power
to a recording studio, video or film production facility, broadcast
station, etc. Its purpose is to drastically reduce hum and buzz
caused both by ground currents from power supply filtering and
by radiation from supply cables into sensitive signal sources like
guitar pickups, tape heads and microphones. Its effect is
startling! It not only dramatically reduces the noise floor but also
noticeably improves dynamic range and sonic clarity.

The IT-1230's heart is a specially wound and shielded
toroidal isolation transformer with a center-tapped secondary. It
is housed in a 3-unit (5.25" high) rack mount chassis. The back
panel provides a 30-amp twistlock inlet and outlet, plus ten 20A
balanced Edison outlets, widely spaced with plenty of clearance
for “wall warts”; the front panel provides two more outlets. An
IT-1230 can be installed in minutes, though you may require some
help in choosing and wiring an appropriate supply cable. The
IT-1230 provides clean and completely safe power—there is no
need to “lift grounds” or compromise the integrity of safety ground
wires to achieve hum reduction.

Special features include an accurate, self-checking AC
voltmeter that not only measures normal voltages, but also flashes
eye-catching special pattern alerts for off-scale but not extreme
conditions (80-90 or 130-140 volts); an Extreme Voltage
Shutdown circuit to cause a protective shutdown if the unit is
exposed to dangerous voltages (like accidental connection to
220V); and a special “Soft Start” circuit to prevent the large in­rush surge currents and spikes that would otherwise occur at turn­on and turn-off with such a large transformer.

960129-2332

Background

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. 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—long before any EMI-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 short circuit.
This unbalanced scheme causes 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 low­level audio signals. Second, because the impedance of chassis
and cable shielding to ground is not zero, ground current flowing
from power supply capacitors and from EMI pickup causes a volt­age drop at 60 Hz and its harmonics which is added to 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 equal and opposite lines of 60V each (referenced to the safety
ground connected to the center tap), which add to 120V. This
type of power, when run around a room, does not induce hum
into nearby audio wiring, because the two power 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. All such systems
are doomed to yield only mediocre results because of the
impossibility of reducing the ground impedance to zero. The
common-mode rejection of a truly balanced AC supply is far
simpler, cheaper, and more effective.

Balanced, or “technical” power, is recognized by the US
National Electrical Code (Article 530) for critical, low noise appli­cations.

Installation

The power source to which the IT-1230 is connected must be
adequate for use at 30 amps. We recommend a 30 amp circuit,

BREAKER

INPUT

80 - 140 VAC

60 HZ 30 AMPS MAX

MADE IN U S A

60 / 120V 1 Ø AC

GFCI PROTECTED

30 AMPS MAX

RISK OF ELECTRIC SHOCK. DO NOT OPEN.
REFER SERVICING TO QUALIFIED SERVICE
PERSONNEL. TO REDUCE THE RISK OF FIRE
OR ELECTRIC SHOCK DO NOT EXPOSE THIS
EQUIPMENT TO RAIN AND MOISTURE.

CAUTION!

60 / 120V 1 Ø AC

GFCI PROTECTED

20 AMPS MAX

RISQUE DE CHOC

ELECTRIQUE — NE PAS OUVRIR

GROUP

WARNING — TECHNICAL POWER
DO NOT CONNECT TO LIGHTING EQUIPMENT.

B

FOR ELECTRONIC EQUIPMENT USE ONLY.

20

20

BREAKER

GROUP

60 / 120V 1 Ø AC

GFCI PROTECTED

20 AMPS MAX

AVIS:

A

(INCLUDES FRONT
PANEL OUTLETS)

IT-1230 Rear View

wired with 10 gauge wiring, if continuous operation near 30 amps
is anticipated. A dedicated (nothing else connected) 30
amp circuit is the minimum acceptable to comply with NEC
requirements. Consult a qualified electrician if in doubt.

The IT-1230 is designed for mounting in a standard 19-inch
rack. Because of its weight, the best position for it is at the bottom
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
ALL equipment in an installation is powered with it. Therefore, try
to position the IT-1230 in a central location so its power can be
easily distributed everywhere it’s needed. If the total power con­sumption of all equipment exceeds 30 amps at 120 volts, delete
high level or mechanical devices first (such as power amps,
etc.). If possible, physically isolate any such 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-1230 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-1230 in a rack that has rear as well
as front mounting rails, you may wish to order adjustable rear
rack ears from Furman. They allow the IT-1230 to be securely
attached both in front and in back. Order model RRM-2.

Operation

Circuit Breaker/Switch: The IT-1230 has just one control:

the large blue switch on the front panel that is both a precision
magnetic circuit breaker and an on-off switch. This breaker will
trip (snap to the “off” position) if the total current drawn through
the IT-1230 exceeds 30 amps. If this occurs, reduce the load by
unplugging some equipment, then flip the switch back to “on.”

LINE VOLTAGE

90

100 110 120 128

AC VOLTS

Mains Voltage Status Voltmeter Reading Outlets

Below 80V Extreme (Shutdown) Meter off—Extreme Voltage LED flashes OFF
80-90 Low Marginal The LED beneath the 90V mark flashes ON
90-104 Low Meter Reads in Low Red ON
106-108 Medium Low Meter Reads in Low Yellow ON
110-120 Normal Meter Reads in Green ON
122-124 Medium High Meter Reads in High Yellow ON
126-128 High Meter Reads in High Red ON
130-140 High Marginal All Meter LEDs Flashing ON
Above 140V Extreme (Shutdown) Meter off—Extreme Voltage LED Flashes OFF