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Positive Feedback ISSUE 57
september/october 2011



Ground Control - On the Final Approach

as reviewed by Bruce Kinch








Amphion Xenon.

Herron VTPH-1 tube phono and VTSP-1/166 preamplifier, and a Michael Yee PA-2 amplifier. Aqvox 2 Ci Mk II phono stage , Bent Audio TAP Transformer Volume Control, Bel Canto e.One M300 monoblock amplifiers.

Nottingham Analogue Spacedeck, Rega Planar 3, Thorens 121, and Logic turntables. Lyra Lydian Beta, van den Hul MC-10, and Grado Sonata cartridges. Modified Denon 2910 CD/SACD/DVD player.

JPS, van den Hul, Nordost Heimdahl, and Reality Cable interconnects. Eichmann Express 6 II, Nordost Red Dawn II speaker cables.

An accumulation of the usual bricks, mats, cones and pucks.


AudioPrism is a small Hi-Fi specialist company with a fine history of offering cost effective tweaks. Their CD Stoplight was one of the first "treatments" for the plague of early digititis—a homely little green marker pen used to paint the edges of CDs, thus to reduce internal reflections that might trigger error correction circuitry. It worked for many if not all players, but it also gave the bits-is-bits crowd an easy cheap shot at "audio-fool" tweakery in general that may never go away. AudioPrism has also marketed effective Isobearing vibration absorbing footers as well as well-regarded AC filtering devices and conditioners.

Ground Control is AudioPrism's name for a suite of innocuous little widgets that are intended to fix a problem most audiophiles didn't know they had. Well, that in itself is not unusual. There are plenty devices out there whose sole purpose is to keep all those frisky little electrons in line and the various radiant fields they engender from mucking up the sound. Many of which may/can/do work, even if the manufacturer's explanation of how and why seems to defy common sense, the laws of physics, and the prudent allocation of funds in a down economy.

AudioPrism's own description of the Ground Control devices is more than a bit vague. There's not even much about them on their website. If you ask the Google for info on the Ground Control thingies, you will find some web-zine and user reviews, the takes ranging from Best Tweak Ever to No Real Change to Made the Sound Worse. To some, that smells of snake oil. Alternatively, one can read that result as something very system and subjective-taste dependent. AudioPrism is refreshingly candid on the topic, emphasizing that the results will differ depending on the design of the components involved, and encouraging experimentation. At least one vendor (Music Direct) offers a 30-day money back guarantee as I write this, if you only tweak while sitting on a fence.

I've had mine for more than 30 days—I acquired a set for review at RMAF last October. I told Byron Collett, Mr. AudioPrism, that my system had been mothballed for about two years—a home remodel project that seemed to have a life of its own, a decision to sell the house when done, six+ months on the market, a cross country move to a new home where other priorities (e.g., her kitchen) would take precedence. So it took a while, Mea Culpa, but I'm back up and running. I don't recall if anyone else at PFO has formally reviewed the GC's, but here I go.

Grounding issues in audio are usually not sexy enough to garner much attention. Sure, most audio components are grounded (or earthed in the UK) like most other (but not all) electrical appliances via the third pin of the common AC plug. That in turn connects to modern building code-required household wiring with a separate ground wire that goes from the receptacle to the breaker/fuse panel. From the panel runs a heavy bare copper cable typically clamped to the under-GROUND water pipe where it enters the building, which thus connects the audio system to the rest of the industrialized world. AudioPrism is not alone in thinking this is not a salubrious situation. Some audiophiles will drive a long copper stake in the dirt to create a dedicated ground for the system as this can audibly improve the sound, lowering the noise floor, reducing hum, etc., simply because this isolates the audio gear from everything else in the house and the world beyond.

Most commonly discussed grounding problems in audio concern hum-generating ground loops (multiple paths to ground); solutions include star-grounding to a single component (often the pre-amp), or lifting/floating the problematic ground on the $1K power cord with a $.59 3 prong-to-2 cheater plug; some components even have a switch to do so. Other gear may have 2-wire power cords or wall-warts without a direct ground connection, or run on batteries or are passive (some preamps, for example). In an audio system, the outer collars on the RCA jacks (or 3rd pin on an XLR) connect the chassis grounds of the various components. So there is in effect a ground circuit in an audio system superimposed on and in addition to a signal circuit.

AudioPrism's literature posits the need for a "local ground plane", such as employed in early (i.e., ungrounded 2-wire era) audio equipment, as essential for conveying the detail and richness of the musical signal. Interestingly, it suggests this is true for loudspeakers as well as active components. To wit: "Ground Control provides a self-contained local ground storage mechanism", which apparently collects "electrostatic moments". (I'm not sure what that means, either.) Clearly, however, these are not reconfigured RFI/EMI filters, Zobel networks, or other well-known add-ons.

The AudioPrism Ground Control units come fitted with RCA, spade, or banana connectors, in two levels: Standard (copper) and Reference (silver). Connectors are from highly regarded Xhadow. The devices are attached to the outer cowl only (i.e., no center pin) of an unused RCA jack on a source component or preamp, and/or the Negative binding post only of a loudspeaker (optionally to the negative post of the amplifier output as well to increase the effect.) The works are sheathed in what appears to be a slender cotton sock, with a branded clasp at the end. My understanding is they are basically carefully measured and coiled loops of many feet of ultrafine wire.

To be honest, my samples sat in my sock drawer for months. I finally unpacked and began setting up my system as it had been configured in New Mexico over the summer. It sounded dreadful. Two years in storage, and I figured everything—speakers, cables, electronics—needed breaking in all over again. I cleaned and conditioned all the connectors. I installed a dedicated AC line and the Oyaide receptacle, and detached, burnished, and reattached the house ground cable. I daisy chained cables to the Hagerman Frycleaner for a few days, hooked everything up, put a burn-in CD on repeat, turned it up and took off for a week's vacation.

Upon return, things were better, but…

I started moving the speakers and listening chair around, taking measurements and listening to the changes. My old room in New Mexico was adobe, with zero sonic leakage/absorption through the walls. Without judicious room treatment and careful selection and positioning of speakers and listening chair, it could sound like a 300 sq ft shower stall, with huge bass mode issues. Given the reverberant space, at 10' one listened as though in the far field, the soundstage suspended in the ambient aura. With the controlled-dispersion Amphion speakers, designed to minimize room interactions, the system had ended up quite satisfying.

The listening room in our new house is actually a partitioned section of a larger finished and carpeted basement, open on the back (listening) side. The walls are flimsy paneling, and the speakers ended up much closer to the sidewalls, and with more toe-in, than before. Listening at 9 feet, I was clearly still in a near-field environment, with a much different balance of direct and reverberant sound. And there was some residual grunge, frequency and level related, in the upper octaves I couldn't seem to eliminate. I figured some room treatment and further cable changes might fix it.

Otherwise, the system sounded pretty good, thank you. I went upstairs to take a bathroom break, and on impulse, retrieved the Ground Control gizmos, partly out of guilt at the long hiatus, partly to see if I could hear any differences at that point of the system set-up. I put an RCA Ground Control on the CD player. A spade dongle on each speaker's negative terminal. One more spade on the preamp's ground terminal, another on the phono stage ground. Had some lunch and sat down to listen. Pushed play.

It was one of those OMG moments. The sound had gone from good enough to Wow.

At shows like RMAF, one hears lots of lush female vocals, the Diana Krall kind of audiophile stuff. Not for me. I had been listening a lot to Kate & Anna McGarrigle's Heartbeats Accelerating (CD). The sisters' light and slightly rough voices highlighted the upper octaves grunge issue noted above. The studio recording was probably never up for an engineering Grammy, but features plenty of acoustic and electric instruments, synth, layered backup vocals, and subtle percussion fills. The tunes stick with you, and the lyrics are, well, dark enough to send a chill up the spine.

Suddenly, the soundstage had expanded in all directions; the tonal density and textures increased, each entry somehow more prominent in the mix. Attack and sustain, ambience, dynamics and focus all markedly improved, everything just opened up. It became much easier to separate the sisters' similar voices both in timbre and space. High frequency transients and sibilance were pristine, clean and controlled. While the clarity was improved throughout the mid-range and bass, the overall balance seemed shifted a bit toward the treble—but with the increased transparency, I was all too happy to crank it up. Disc followed disc, the benefits equally obvious with massed strings, brass timbre, keyboard attack and sustain. Removing the dongles and replacing them sequentially over several days confirmed while one can hear a difference upon insertion, the contribution of each was additive, and the overall effect increased over time, and gradually receded as the individual units were removed.

Also came the WTF moments. As I had been swapping three XLR cables in an attempt to resolve the treble congestion issue before adding the dongles, I decided to revisit the comparison. Curiously enough, my ranking was now reversed. The previously lackluster cable suddenly trounced the other two, and by a fair margin. I've never known a tweak to do that.

Naturally, I switched to analog. I haven't set up the Nottingham deck yet, so just dragged in the Rega Planar 3 I use in my workroom, but it sounded quite fine indeed, similar improvements (clarity, extension, dimensionality) noted, but the high frequencies sometimes seemed a bit too hot until I changed the MC cartridge loading. But I realized that the effect of the Ground Control thingees was much like the results of demagnetizing a MC cartridge. On steroids.

That night PBS broadcast a Mostly Mozart concert from Lincoln Center. We have a modest Home Theater setup, a Marantz receiver feeding a 50" Panasonic plasma and 5.1 speakers. The fine young American Susannah Phillips sang two Mozart arias. Between them I stuck a RCA Ground Control on the Marantz. Damn, she was better.

So put me on the Best Tweak Ever squad. Of course, the YMMV moment has arrived. If, like some audiophiles, you have tended towards tweaks and gear that are inherently bright in search of increased resolution, the Ground Control approach may not flatter the system. Like myself, you may want to reconsider such preferences. I tend to prefer balanced XLR cabling to single-ended RCAs, the Bent Audio TAP transformer-based preamp is extremely transparent and essentially passive, the Rega turntable ground is combined with the signal leads, and I suspect the Cambridge Audio CD player's output has a bit of DC offset. As noted, I was in full-system burn-in mode in an unfamiliar room when I first installed the Ground Control bits. I was listening carefully for changes as the cables and components "settled in", and the Ground Controls may have enhanced that still mysterious process. Any of the above might be significant in accumulating electrostatic moments. Don't know.

I also don't know how or why these things work. I don't know if a system with a dedicated ground would find them as beneficial. I don't know if the various shielding/grounding tricks cable manufacturers employ would affect the results.

Or if they will work with electrostatic or active speakers.

I do know they worked a treat in my system. I don't know if the "Reference" versions are worth the up charge at this point, but I may well have to buy a couple more to be sure. Maybe 5.1 more, even if the home theater speakers cost about what the Ground Control gizmos do. Money back if not satisfied? For a tweak! Bruce Kinch

Ground Control
Various units are $99 to $249, depending on connectors

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