16 dB improvement in back ground noise floor in systemwide installations
Features:
Toroidal transformer with center-tapped secondary is the
Exclusive "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 (spike suppression, RFI filtering) plus gas discharge tube to dissipate spikes
Ground fault interrupter (GFCI) protection
DESCRIPTION
Designed for the most critical, ultra-low-noise installations, the IT-1210, IT-1220 and IT-1230 can supply 10, 20 or 30 amps respectively of balanced AC power to a recording studio, video or film production facility, broadcast station, etc. Their 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 and microphones. The effect of the IT-1210, IT-1220 and IT-1230 is startling! They not only dramatically reduce the noise floor but also noticeably improve dynamic range and sonic clarity.
At the heart of all three models is a specially wound and shielded toroidal isolation transformer with a center-tapped secondary. The IT-1210 is housed in a 2-unit (3.5" high) rack mount chassis; the IT-1220 and IT-1230 in a 3-unit (5.25" high) rack mount chassis. The IT-1210 and IT-1220 back panels (see drawings on overleaf) provide 12 outlets, spaced to allow clearance for "wall warts"; the front panel provides two more. The IT-1230 provides ten 20A outlets, one 30A twistlock outlet and one 30-amp twistlock inlet in back plus two 15A outlets in front. Front outlets are Ground Fault Interrupter protected. All outlets are balanced.
An IT-1210 or IT-1220 can be installed in minutes without the need for an electrician; the IT-1230 may require some help in choosing and wiring an appropriate supply cable. All three models provide 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 Furman's exclusive "Soft Start" circuit to prevent the large inrush surge currents and spikes that would otherwise occur at turn-on and turn-off with such a large transformer.
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 low-level audio signals. Second, because the impedance of chassis and cable shielding to ground is greater than 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 60V lines of opposite polarity (referenced to the safety 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. All such systems are doomed to yield only mediocre results because of the impossibility of reducing the ground impedance all the way to zero. The common-mode rejection of a truly balanced AC supply is far simpler, cheaper, and more effective.
Balanced power is a technology whose time has come. Balanced power is recognized by the National Electrical Code (Article 530) for technical power applications. Its use is restricted to electronic equipment only. Balanced power may not be used for lighting equipment, and access must be restricted to use by qualified personnel only.
Note: Because of its 20 amp rating, the IT-1220 uses a special AC plug. Click on the link to find out what to expect, so your installation is not delayed. The IT-1230 also uses a special twist-lock power inlet.
IT-Series SPECIFICATIONS
Output current:
IT-1210: 10 amps (1200 watts at 60/120 V 1Ø AC, 60 Hz)
IT-1220: 20 amps (2400 watts at 60/120 V 1Ø AC, 60 Hz)
IT-1230: 30 amps (3600 watts at 60/120 V 1Ø AC, 60 Hz)
Voltage Ranges:
Normal, 90-130; Marginal (flashes alert), 80-90 or 130-140;
Extreme (causes shutdown), below 80 or above 140
Inlets:
IT-1210: Heavy duty power cord with three-prong plug
IT-1220: Heavy duty power cord with 20A three-prong plug
IT-1230: One 30A NEMA L14-30P twistlock connector
Outlets:
IT-1210: 12 rear, 2 front, each rated at 10A
IT-1220: 12 rear, 2 front, each rated at 20A
IT-1230: Ten 20A outlets and one 30A NEMA L14-30R twistlock outlet in back, plus two 20A outlets on front. Front outlets are Ground Fault Interrupter (GFCI) type.
Isolation, Input to Output:
Breakdown Voltage: 1500V minimum.
Leakage current: 40 mA maximum.
Capacitance: 300 pf maximum
Turns Ratio:
1:1; windings separated with Faraday shield
Transformer Regulation:
(Full load/no load) 3% at full load
Spike Protection Modes:
Line to neutral, neutral to ground, line to ground
Spike Clamping Voltage:
TVSS rating of 400 volts peak, L-N, N-G, L-G (tested to UL-1449)
Spike Response time:
1 nanosecond
Maximum surge current:
6,500 amps (8 x 20 mS pulse)
Maximum spike energy:
80 joules per mode, 240 joules total
Noise attenuation:
Differential mode: Greater than 40 dB
Transverse mode: Greater than 60 dB
Common mode: Greater than 80 dB all 1 to 200 MHz
Mechanical:
Dimensions:IT-1210: 3.5" H x 19" W x 17" D. IT-1220/30: 5.25" H x 19" W x 17" D.
Weight: IT-1210: 40 lbs (18 kg)
Weight: IT-1220: 65 lbs (30 kg)
Weight: IT-1230: 72 lbs (33 kg)
Construction: Steel chassis, powder coated; glass epoxy printed circuit boards
Power Consumption:
8.5 watts for display and control circuits, independent of actual load
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