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September 2002
Enjoy the Music.com Review Magazine
Q's The InterFace Ground Loop Solutions
Or The Spanish Inquisition
Review by Steven R. Rochlin
Click here to e-mail reviewer


Q Audio The Interface Gound Loop Solution  After suffering through boxing all my belongings, moving to a new home, and then unboxing and setting things up, the usual problems reared their ugly heads. First came the usual settling time and burn-in of my music reproduction system. While one would feel that having thousands of hours on a unit would make it "good to go," it seems that it took about a week for things to truly relax in their new environment. So after a week i began to tweak and tinker and discovered the dreaded "cable TV ground loop" problem. This manifests itself with that annoying 60Hz buzz sound. Unhooking my digital cable TV output from my reference system also eliminated the buzzing (ground loop) problem, but then where is the advantage of paying $$ for pure digital surround sound audio and all those great music channels i am paying for, let alone watching HBO, Showtime, etc. in all their digital glory (Is the phrase "digital glory" an oxymoron? Perhaps.). In any case, i decided to find a solution.

In my huge "Bag Of Tricks" (like Felix the Cat) are more weird tweak devices ranging from the most pedestrian 30 gauge Tandy/Radio Shack magnet wire to FM modulators, silver wire jumpers, built-in attenuation RCA cables, wacky adapters, an abundance of power supplies... and a cornucopia of transformer-based devices that claim to improve the sound of your sound system by removing Satan himself or some such from your home. If good Karma is something akin to being in the right place at the right time most of your life, then my life is filled with such experiences... even when something at the time was considered "bad", yet in hindsight it was a blessing. Go figure!

Approximately two days before moving to my new humble abode this small package came in the mail. While i do not recall asking for Q's The InterFace, there it was at the worst possible time. All my equipment was well packed and marked awaiting the movers. Last thing needed was to keep track of a small rogue box that would set me back almost $900 should i lose it. "Damn them!" i howled to the sky as i stuffed this small box into one of the last minute boxes marked "Assorted Important Crap"... and so begins this review.


What Is Your Name?

 Q's The Interface ($875) is said to, eh hem, supercharge single-ended (RCA) inputs and is also capable of being employed for those with ground loop problems. This well-crafted box features lovely wood accents and super beefy WBT female RCA jacks. Definitely not home-brewed so it seems. Q employs the Jensen JT-11P-1 audio input transformer due to its wide and nearly ruler-flat bandwidth (-3dB at 0.25Hz and 100kHz). Each transformer is precision-wound on a highly-specified nickel/molybdenum/iron core and then potted inside a grounded, Mumetal case. The Interface is said to achieve 100dB at 60Hz (68dB at 3kHz) of common-mode noise rejection, making their single-ended (RCA) unit compete with the advantages of balanced (XLR) lines, yet allowing the user to possibly have less overall circuitry in the signal chain.


As seen above, there are very few, yet all very high quality parts. The wire is pure silver by Kimber Kable. There appears to be no cost-cutting measures in this design. The InterFace seems to be a cost-no-object device with a keen eye (or ear as it were) on interfering with the critical analog signal as little as possible.


What Is Your Quest

According to Q's website "A ground loop is created whenever two grounded, single-ended components are interconnected. A grounded component (as opposed to floating) is one which ties the signal reference ground to the AC safety ground (the "third pin" on an AC power cord). The loop is formed by the safety ground leads of each component's AC power cord--which are effectively tied together at the AC receptacle--and the ground leads of the interconnects. In addition to suffering from the interchassis currents mentioned above, grounded components also pick up any noise currents which exist between the safety ground pins of the two AC power cords. Plugging the two components into the same AC receptacle can minimize these noises, but as with interchassis current noises, they cannot be eliminated." This is a common problem for many of us who desire integrating our high-end system with cable TV. In other words, The InterFace's job is to communicate the pure signal while removing nasty ground loop problems and impinging as little footprint of its own as possible. Not an easy task.


What Is Your Favorite Color?

Now before you start sending me mail about using two 75ohm to 300ohm adapters back to back to eliminate cable TV ground loop problems, i did not want this type of solution. Why? Because i am weird and wanted as pure a digital cable signal as possible in my fringe reception home. As The InterFace was here and could be tested/reviewed, it was the right tool for the right job. Good Karma reveals itself in many forms.

The InterFace had some competition including some device from my previous Car Audio Craze days. Not sure who made the car audio ground loop elimination device in question, yet it did indeed work. As i recall, it set me back about $30 at some flea market in Florida. While it also used transformers, the sound i was achieving apparently reduced the definition of deep bass (below 50Hz). Was quite surprised how well defined the midrange was as the highs were silky smooth and clean. Not too shabby for a $30 investment many years ago! As time went by, i noticed analog surround sound was experiencing some peculiar problems. There must have been some phase shifting going on as though someone took the front soundstage and super-wide processing. Ahh, well it was only $30 from a flea market...

Inserting The InterFace after thorough burn-in in the basement, there was zero ground loop problem while bass was much cleaner. Better still, the super-wide processing that afflicted the cheaper solution was gone. Now sounds were more appropriate. All other frequencies emerged virtually equal, if a tad more transparent, than the much cheaper $30 solution. Still, for the difference in financial outlay there had better be more to this story... 

Only towards the very end of my review process did i receive an e-mail from Steve Eddy of Q who requested i also try the unit between my DAC and pre-amplifier. Here is where The InterFace showed total supremacy over the much cheaper solution. To my ears in my system, the sound was a bit smoother in the midrange without any suffering in definition. It is akin to tube swapping to some degree, yet less so. How to better explain this. Think of a great cup of espresso, yet one has a bit more dimension and lacking even a hint of bitterness due to proper grinding of the bean and just the right amount of tamping. My apologies to those of you who do not speak espresso-ese. In the end i suggest auditioning The InterFace and make your own conclusions.

Many of the DIY guys are no strangers to using transformer-coupled stages. In fact exotic and highly respected Japanese amplifier manufacturer WAVAC Audio Lab and also British based Audio Note use this type of design. Meanwhile there is an entire article on the Jeff Roland Design Group Website concerning this subject and, specifically, the Jensen's JT-11P-1 transformers as found within The InterFace. So we have highly respected companies from both tube and solid-state camps apparently singing the praises of the Jensen's JT-11P-1. Time for an inquisition!


Nobody expects the Spanish Inquisition! Our chief weapon is surprise... surprise and fear... fear and surprise.... Our two weapons are fear and surprise... and ruthless efficiency.... Our three weapons are fear, surprise, and ruthless efficiency... and an almost fanatical devotion to the Pope.... Our four...no... Amongst our weapons.... Amongst our weaponry...are such elements as fear, surprise.... I'll come in again.


Nobody expects the Spanish Inquisition! Amongst our weaponry are such diverse elements as: fear, surprise, ruthless efficiency, an almost fanatical devotion to the Pope, and nice red uniforms - Oh damn!


And i would add Q's The InterFace to my weaponry within the "Bag Of Tricks". It impedes very little on the audio signal while removing the nasties of ground loop problems. As for how it "sounds" between other devices, it would be more a way to help shape the sound of your system, possibly adding a bit of smoothness. Of course in the end what really matters is that you...


Enjoy the Music,

Steven R. Rochlin



Frequency Response: 0.25Hz to 100kHz (-3dB)

Input Impedance: 13kohms

Deviation From Linear Phase: No greater than 0.6 degrees, 20Hz to 20kHz

Distortion (THD+N): Less than 0.001% at 1kHz

Common Mode Rejection (CMRR): Unbalanced source:
100dB at 60Hz
68dB at 3kHz

Balanced Source:
107dB at 60Hz
73dB at 3kHz

Dimensions: 2.5 x 5 x 4 (HxWxD in inches)

Weight: 2.1 lbs.

Warranty: fully transferable, 10 year limited warranty on all parts except transformers which are covered by a 20 year manufacturer warranty

Price: $875


Company Information

9941 Horn Road, Unit A
Sacramento, CA 95827

Voice: (916) 457-7946
E-mail: info@q-audio.com
Website: www.q-audio.com













































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