June 2003

Furman Sound IT-Reference Discrete Symmetrical AC Power Source Review
An engineered balancing act in power for recording studios and home audio systems.
Review By Steven R. Rochlin

  For those keeping scores, symmetrical power (also referred to as balanced power) first hit the audiophile scene due to my review in the now-defunct print publication Ultimate Audio. Way back in November of 1997 my review of the Furman Sound IT-1220 had a huge impact on those who were (at the time) offering the usual filters and whatnot. We will avoid the Tice Clock and other interesting offerings back "in the day" and simply recognize that many experts in their field woke up, as it were, to realizing that proper engineering should indeed be sought over more unique (avoiding using the words "snake oil") designs. Having run the gambit of dedicated power (a must-have for every audiophile) and various power filtering devices, it felt good to find a proper, based on engineering fact solution.

The Geek Files
The power running into our listening rooms here in America consists of three wires. The 120-Volt positive wire (also called the hot wire), the neutral wire, and then the neutral wire is tied to the third wire which is the ground. The positive wire is usually not separately shielded and, therefore, free to interact with the others causing problems. Another quandary most of us have experienced is those nasty ground loop hums and buzzing due to the impedance of your equipment's chassis and interconnect shielding to ground not being zero. If you live in a big city then you can top all this off with the usual line pops, Radio Frequency Interference (RFI), Electromagnet Interference (EMI), and more noises that can drive us nuts!

Symmetrical (also referred to as "balanced") power has been recognized by the U.S. National Electrical Code (Article 530) as an effective and safe method of power distribution. Symmetrical power also uses three wires like we use today, but in a manner that makes sense.

[ Utility AC Source ]
│
│ Primary: 120V AC
▼

+----------------------+
| Isolation Transformer|
| (Primary Side: 120V)|
+----------------------+
│
│ Secondary: 120V AC,
│ center-tapped for balance
▼

+-----------------+
| Secondary |
| Winding |
| (Center Tap) |
+----┬-------┬----+
│ │
│ │
L1│ L2│
(Approximately +60V) (Approximately -60V)
│ │
+---[Load]---+
(120V balanced)
│
Center Tap (0V, Ground-Reference)

Explanation Of The Above ASCII Diagram
Utility AC Source: The system begins with the normal mains supply, which is fed into the primary winding of the isolation transformer.

Isolation Transformer: This transformer serves two key functions. First, it provides electrical isolation from the mains supply, which can improve safety and reduce interference. Second, its secondary winding is designed so that it produces a balanced 120 V output across its two terminals by using a center tap.

Secondary Winding and Center Tap: The center tap is connected to earth ground (or the system’s common reference), ensuring that the two output legs are mirror images relative to ground: one at about +60 V and the other at about –60 V. The 120 V rating is the difference between these two balanced outputs.

Load Connection: The balanced load is connected between L1 and L2. Devices receiving this balanced power benefit from the cancellation of common-mode noise and a reduction in potential ground loop issues.

More Information Concerning Balanced 120-Volt Power
It uses a 60-Volt positive wire, a 60-Volt negative wire, and then a ground wire. Benefits? No more power line-induced noises affecting nearby audio wiring because the positive and negative leads cancel each other out just as they do with balanced analog audio (XLR). The ground currents that may cause ground loops from the non-symmetrical scheme are virtually eliminated! The icing on the cake here folks is that by balancing your entire system you will typically get up to 24dB improvement in reducing background noise. Use symmetrical power for all your music reproduction components for the best results.

As for the basic differences between the new (IT-Reference on top) and old units (IT-1220 on bottom), seen above are the front panels. Furman Sound has eliminated the LED meter and front GFI plugs. All electric connections on the IT-Reference appear on the rear panel (as pictured below). The new unit also has a much cleaner, more modern look overall. While the older unit is standard 19 inches wide for rack mounting, the IT-Reference conforms to the standard 17 inches wide as found in most consumer gear. Furman Sound does offer "ears" to make the IT-Reference 19-inch rack mountable.

The newer unit employs more transformers set in "power banks" to provide for equipment consuming moderate power, thus eliminating digital noise and performance-degrading power supply backwash from neighboring components. The electrical outlets are individually isolated, electrostatically shielded, positive contact "Super Spec" and are individually ground fault (GFCI) protected to ensure safe operation.

The Furman Sound IT-Reference also has a precision high-inrush magnetic circuit breaker/power switch to supply maximum protection, while maintaining the lowest possible contact resistance. Lastly, the older unit (bottom) has a permanent electrical cord while the new (top) unit has an industry standard IEC jack to allow for those who desire aftermarket power cords (such as our esteemed reviewer and power expert Bill Gaw). All in all the new unit does not just build on the older; it is a new and carefully implemented design. Bravo Furman Sound!

The Proof Is In The Pudding
Instead of simply rehashing my over-five-year-old review of the previous Furman Sound IT-1220 that has served me well over these many years, want to start with a clean slate. The IT-Reference is a substantial unit (80 lbs.) and built like the proverbial tank. The outlets on the rear are marked and firmly grasp all my power cords. Upon turning the unit on you will hear a click and the centrally mounted blue LED lights up. No hum, no buzz, and no annoying extraneous noises are heard afterward. The unit simply works without complaints or distractions. While the LED power meter on the older unit adds assurance, my belief is in the "less is more" camp. This also applies to those power devices that "regenerate" power.

Am sure many engineers out there wonder how a power unit can magically add or "reconstruct" power without also adding more parts in the electrical path, thus further complicating matters. This reminds me of those, such as myself, who prefer unregulated power supplies to tightly regulated ones. There are good arguments for both camps and simply pick a side of the fence you choose to sit on and go with it. My preferences have now been noted.

Unlike our well-seasoned power guru Bill Gaw, or those who live in New York City, the electricity to my home is amazingly clean and constant. There was already a dedicated electrical outlet exactly where it should be in my listening room. Adding to this the benefit of a new power transformer and wire installed by the power company only weeks after moving in. As written in one of my previous articles, "Some days you are the dog, others you are the hydrant." In this care, I feel like the Big Dog as my new home has been nothing but day after day of pure joy. Sometimes the Audio God, She of Great Wisdom, smiles upon thee. So why would someone in a great situation such as myself need symmetrical power? The answer is simple... the power you feed into your electronics matters!

While there is little doubt of the quality of power supply within my current reference system [basically, Voyd turntable, Assemblage DAC-2 (heavily modified), Audio Alchemy DDS-III transport (heavily modified), conrad-johnson Premier 17LS pre-amplifier, and Wavelength Audio Cardinal X1 monoblock tube amplifiers], providing symmetrical power decreases the possible problems of EMI and RFI. It also allows for the power supplies to have the same positive and negative voltages. And the results are....

Results Speak For Themselves
In my room with my equipment, a dead quiet back background, beautifully portrayed harmonics, astonishing macro and micro dynamics, gobs of inner resolution, and an overall ease of portrayal. Soundscaping had more ease to it, though should admit many visitors have heard the amazing freedom of imaging my system portrays. It is a very natural experience as my room simply takes on the size and acoustic properties of whatever is within the recording. Yes, my systems had all the previous in spades, yet using the new unit simply allowed for a tad bit more of the same. This should not be taken as the Furman Sound unit providing small benefits, it should demonstrate that even under the best of circumstances an improvement could be produced.

Those of you with less than nearly perfect power, such as myself, will probably experience higher quantities of the benefits heard in my humble abode. While you (generally) will not find Furman Sound in audiophile stores, it can be purchased from professional audio dealers. While at your pro audio shop have a look around at the offerings by Behringer and others. In my humble opinion, audiophiles should recognize the benefits of certain professional products that may also priced more appropriately. Furman Sound should be highly commended for being at the beginnings of symmetrical power and further refining its products over the years. Sane engineering employed with top-quality parts yields added benefits to their users. As always, in the end what really matters is that you...

     Enjoy the Music,

    Steven R. Rochlin

Specifications
AC Current Capacity: Continuous: 12 Amps. Peak: 20 Amps (maximum combined from all outlets)

Noise Attenuation: Transverse mode: >80dB Common mode: >80dB, 1-200 MHz System Noise Reduction: typically >24dB 

Outlets: 8 (symmetrical balanced) 4 (power corrected amplifier circuit)
Dimensions:5.5 x 16.9 x 15.9 (HxWxD in inches)
Weight: 80 lbs.
Power Consumption: 8.5 Watts for display and control circuits independent of actual load
Optional mounting ears for standard 19 inch racks available
Warranty: Three year limited warranty covering defects in materials and workmanship
Price: $3,250

Company Information
Furman Sound, Inc.
1997 South McDowell Blvd.
Petaluma, CA 94954

Website FurmanSound.com