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Furman Sound IT-1220 AR-15 II PS-PRO II PST-10D Power Conditioning Products

These days virtually every studio is piled miles high with computers and other sensitive equipment. It is no surprise that Furman Sound has a host of new and not-so-new products perfectly equipped to protect and improve the performance of this gear.

These days virtually every studio is piled miles high with computers and other sensitive equipment. It is no surprise that Furman Sound has a host of new and not-so-new products perfectly equipped to protect and improve the performance of this gear. The first is the IT-1220 Balanced Isolation Transformer which provides the balanced power that many studios have been boasting about for years. The other three boxes, the AR-15 II the PS-PRO II and the PST-10D all offer power conditioning, Linear Filtering Technology (LiFT), and Series Multi-Stage Protection (SMP) as well as a host of other features.


IT-1220 Balanced Power Isolation Transformer

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The IT-1220 ($1,599), designed for the most critical, ultralow-noise installations, is the ultimate power device. The unit supplies 20 amps of balanced AC power to a recording studio, video or film production facility, broadcast station, etc. Its purpose is to 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 box not only reduces the noise floor but it also improves dynamic range and sonic clarity. The box is built around a specially-wound and shielded toroidal isolation transformer with a center-tapped secondary transformer and can be installed in minutes without the need for an electrician.

The IT-1220 includes 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 (80V – 90V or 130V – 140V). The Extreme Voltage Shutdown circuit causes a protective shutdown if the unit is exposed to dangerous voltages and Furman Sound’s exclusive “Soft Start” circuit prevents the large inrush surge currents and spikes that would otherwise occur at turn-on and turn-off with such a large transformer.

North America uses 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 can cause hum in audio circuits. With a center-tapped isolation transformer (as is the case with the IT-1220), 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. In addition, ground currents are all but eliminated by the same common-mode cancellation effect. The IT-1220 typically provides a 16 dB improvement in back ground noise floor in system wide installations. A 30-Amp version of this box (IT-1230) is also available.

AR-15 II – Voltage Regulator and Power Conditioner

(click thumbnail)AR-15 – Voltage Regulator and Power Conditioner
The 15-Amp AR-15 II ($659) provides stable AC power to protect equipment from problems caused by AC line voltage irregularities such as sags, brownouts, or overvoltages. The box accepts input voltages from 97V to 141V and transforms them into a constant 120V, ±5V. In addition, the AR-15 II filters and purifies AC power, reducing line noise and ensuring optimum performance. The box includes Linear Filter Technology (LiFT), Series Multi-Stage Protection Plus circuitry (SMP+), and Extreme Voltage Shutdown (EVS).

Furman Sound’s LiFT evenly suppresses AC noise assuring maximum performance from a system and SMP+ safely absorbs, clamps and dissipates damaging transient voltages. Most protection circuits offer clamping voltages that are above 300Vpk but Furman’s SMP+ clamps at 188Vpk, 133 VAC RMS. This level of protection is only available with Furman Sound’s SMP+ technology. Additionally, Furman’s overvoltage circuitry protects against accidental connections to 208 or 240VAC, by shutting off the incoming power until the over voltage condition is corrected.

The AR-15 II circuitry monitors the incoming line voltage with each cycle, comparing it to an extremely precise voltage reference, accurate to ±0.15%. If a voltage fluctuation requires that a different tap be selected, the new tap is switched electronically at the zero-crossing, to avoid distorting the AC waveform. (Most commercial voltage regulators using multiple-tapped transformers switch taps at uncontrolled times, thereby creating voltage spikes, and often creating clicks that can leak into the audio.) The design is not sensitive to small errors in line frequency, making it ideal for use with generators. Each of the AR-15 II’s outlets are regulated, spike-suppressed, and filtered against RFI. There are no controls except the on-off switch. A bargraph meter comprised of 10 LEDs indicates input voltage, while another LED indicates “In Regulation” status.

PS-PRO II – Power Conditioner and Sequencer

(click thumbnail)PS-PRO II – Power Conditioner and Sequencer
Like the AR-15 II, the PS-PRO II ($399) incorporates Furman’s SMP+ and LiFT technologies. Unique to this box is its ability to power up a rack full of equipment in a three-step delayed sequence. The sequence is reversed for power-down. The sequence can be initiated with either momentary or maintained switches, locally or remotely. A duplex outlet is provided for each delay step. The delay time can be adjusted via a front panel screwdriver adjustment. The box also features a locking switch with a removable key for maximum security. One or more Furman PS-PRO IIs may be installed in remote locations and operated via low-voltage wiring.


(click thumbnail)TST-10D
Instead of being a rackmount device, the PST-10D ($220) is a rather large power strip. Like the AR-15 II and the PS-PRO II, the unit incorporates Furman Sound’s SMP+ and LiFT technologies. In addition, the PST-10D provides telco and cable/satellite transient voltage suppression. This makes it perfect for a home theater and/or computer setup. The box’s 10 outlets include four digital-ultrasonic noise filtered outlets, three linearly filtered outlets and three sequenced linearly filtered outlets. In addition, the PST-10D employs ultrasonic filtering for both digital and video components. The PST-10D features three delayed AC outlets which prevent annoying loudspeaker “pops” and accidental circuit breaker tripping.

The strip can be used with an external 12V sequencer or a receiver with a 12V sens circuit by connecting the sens circuit’s mini phone jack to the 12V input. The three delayed AC outlets can be turned on and off by the remote 12V sens circuit while the other seven AC outlets are still be controlled by the PST-10D’s main AC switch. The power strip features transient voltage surge suppression for both standard telephone lines, as well as cable and satellite lines utilizing standard coaxial connectors. The in-line surge suppressors features Furman’s ground contamination free technology that aids in eliminating audio buzzing, and the video hum-bars that can result from typical in-line suppressors. The cable and satellite suppressors are TIVO and HDTV-compatible.

In Use

I was excited to plug in the IT-1220 and see what all the balanced power hoopla is all about. I’ve worked in a couple of studios equipped with balanced power but I’ve never had the opportunity to actually compare the noise floor of a studio with balanced power to the same studio without it. I must admit, I was surprised. I wasn’t able to do a quick A/B comparison. I actually had to completely power down the studio, add the balanced power and then power everything back up. The entire switch, including the time for the computer to reboot, took approximately four minutes. With this much of a delay, if the difference wasn’t substantial then I wouldn’t even be able to notice it. The difference was so drastic that it made me want to go back and revisit everything that I’ve mixed over the

past decade. I did the same test with the PS-PRO Series II and I wasn’t able to tell a difference (of course this unit doesn’t have the same claims or the same price-tag as the IT-1220). The unit didn’t have any difficulty powering my entire room and it was nice knowing that I had the protection provided by the box. Nashville engineer Scott Heyniger swears by his AR-1220 (a 20-Amp voltage regulator, similar to the AR-15) and IT-1220 combination. By plugging the IT-1220 into the AR-1220, he has eliminated all of his power problems.

The AR-15 Series II and the PST-10D don’t have the power to handle my room but the AR-15 worked well in my Pro Tools rack. It seemed to eliminate a bit of noise as well. One feature unique to the AR-15 Series II and the PS-PRO Series II is the rear lamp. Each of the units has a rear panel mounted BNC connector that allows a standard (12VAC 0.5 amp) gooseneck lamp to illuminate the rear of the rack. The lamp is switched on and off via a front panel switch. Nice thinking.

I found that the PST-10D is perfectly equipped to handle the power issues of a home theater system. When applied to this situation, a television plugged into the digital/video filtered outlets will not affect an audio receiver-controller connected to one of the PST-10D’s standard or delayed outlets. I put the power strip to use in this scenario and found it to work perfectly. Perhaps the best way to decide exactly which Furman product is right for you is to take Furman’s Product Solutions Questionnaire at


Be it size, portability, features, or price, each of the Furman power units has its own strengths and weaknesses. They were obviously designed by people who understand the needs of the end user. From the well-spaced outlets (that actually allow wallwarts to be plugged-in directly) to the sequenced power-up/down to the ultimate in perfect power, balanced power, Furman is equipped to meet the needs of the most demanding audio and video professionals.