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Gryphon Diablo 300

201012_audioprismI’ve enjoyed AudioPrism products for quite a while -- all the way back to CD Stoplight, introduced 20 or more years ago. This is a green paint marker with a notched tip that fits the edge of a CD. You paint the disc’s inner and outer edges with the marker and let it dry. AudioPrism claimed that the green paint absorbed stray infrared reflections of the beam from the player’s reading laser. CD Stoplight has remained one of the most controversial CD tweaks ever since it was introduced.

I am a faithful user of AudioPrism’s WaveGuide and Noise Sniffer. Their other products have included power conditioners, radio antennas, CD Backlight (a luminescent disc to put on the back of a CD during play), and tubed preamplifiers and power amplifiers. AudioPrism’s electronic components were so good that, for a while, they made preamps and amps for Mark Levinson’s Red Rose brand.

AudioPrism went dormant for much of the 2000s, but has now been rebooted by Byron Collet, who was with the company in the 1990s. AudioPrism will bring back many of their older products, along with some new ones -- of which the Ground Control ($149.99 USD per pair) is one.

The Ground Control is claimed to improve the performance of the ground side of loudspeaker and amplifier connections. It would be considered a tweak product by most audiophiles, many of whom consider tweaks a waste of time and money. However, in my experience of tweaks in my own system -- in subjective evaluations, with occasional objective measurements (when possible), and even some blind testing -- tweaks have almost always changed the sound. These changes have not necessarily been huge; some have been for the better, some for the worse, and some have simply been different. But I can’t recall any tweak product that has done nothing to the sound, and the Ground Control is no exception.


AudioPrism states that Ground Controls provide “a self-contained local ground storage mechanism for all of the electrostatic moments that occur in music being reproduced via a given circuit or component. They help to maintain the coherence of electrons involved in signal transfer -- i.e., making music -- through CD players, preamplifiers, amplifiers and, of all surprising things, speakers.”

Ground Controls attach to the negative binding posts of amplifiers and/or the negative terminals of speakers. Various termination options are offered. For this review, I used four Ground Controls with spades for my biwire speaker connections, and two Ground Controls with banana plugs for the negative amplifier terminals.

The Ground Control itself is about 4.75” long, and about the same diameter as the banana plugs AudioPrism uses. The bananas and spade connectors are of good quality, and the terminations seem to be made quite well. A white “sock” of what feels like tightly woven cotton (the material is not specified) covers what seems to be a loop of many fine, flexible wires. What would be this sock’s open end is closed with a small pinch clamp. It would seem to be impossible to disassemble a Ground Control without ruining the sock, and I didn’t feel comfortable dissecting a review sample to see what was inside.

When the terminated end of a Ground Control is connected to a speaker’s or amplifier’s negative terminal, the other end of the Ground Control just hangs there in space, connected to nothing. My understanding of electronics is that an unterminated wire acts as an antenna, and not as a way to improve grounding. But in analog audio, everything you do seems to have some effect on the sound. I’ve learned to take the explanations given for various tweaks with a grain of salt and just listen carefully, without worrying too much about whether or not the explanation makes sense. Sometimes I think that no explanation at all of how or why some of these things work would be better than an implausible one.

The Ground Control is also available terminated with an RCA plug, to connect to an unused input on preamps. AudioPrism says the functionality of this version will greatly depend on the preamp’s own grounding scheme.

Evaluation one

In all of these evaluations, before installing the Ground Controls, I carefully listened twice each to two or three reference tracks that I’ve heard many times. I then inserted three Ground Controls per channel: one each on each speaker’s two negative terminals, and one on the amplifier’s negative binding post for that channel. AudioPrism says you get the most benefit from putting Ground Controls on the speakers, but I’m told that many listeners find that putting them on the amp terminals provides yet another improvement. Then I listened to the same tracks again, at the same volume level.

Something had changed, but it wasn’t immediately obvious what. After some more listening, I noted that in “Try a Little Tenderness,” from Frank Sinatra’s Nice ’n’ Easy (CD, Capitol/Mobile Fidelity Sound Labs UDCD-790), the solo violin that opens and closes the track had a raspy edge without the Ground Controls, and no such edge with them. But by the end of that first listening session, it still wasn’t exactly clear what else was happening.

The second, third, and subsequent evaluations, with different recordings, began to reveal that acoustic stringed instruments of medium to small size sounded smoother and “prettier” with the Ground Controls. All tracks had soundstages that were about 20% narrower, however, and highs that were slightly rolled off. Those slightly rolled-off highs probably contributed greatly to the smoother string sound.

The phrase “20% narrower” should be put in context. I’ve owned and used Vandersteen speakers since the 1980s, and have become adept at setting them up in each listening room I’ve had in those years. My present pair of Vandersteen 3A Signatures have been in my system for almost eight years now -- a long time for an audio reviewer’s reference rig -- and I know with deadly certainty what they sound like in this room. Their soundstage is quite deep, and its width extends beyond the outside edges of the speakers -- with good recordings made in large venues, such as some of the better orchestral recordings, the 3As can make the walls of my room seem to disappear. Height information comes and goes, mostly depending on the recording (many have little or no sense of height because they are multimono rather than true stereo recordings). So when I say that the soundstage shrank by 20% with the Ground Controls installed, I mean that the extension of the recorded space beyond the outside edges of the speakers was sometimes brought right back to those outside edges. Soundstage depth, however, was unaffected by the AudioPrisms.

Evaluation two

But I kept hearing very positive things about the Ground Controls from many users and reviewers, and decided to have a go with them in a completely different environment. A speaker manufacturer (it wasn’t Vandersteen) I visited provided as a testing environment the final-assembly area of his shop: a large room maybe 24’W x 40’L, with two stud walls and two cinderblock walls, and a linoleum-covered cement floor. The listening distance was about 7’, so what I heard had a much higher proportion of direct-radiated sound than it would have in a home-size room, where a greater distance from the speakers would mean that reflected sound would play a larger role. The speakers were $2500/pair two-way bookshelf models that had just been repaired, refurbished, and re-broken-in for the owner. With just one set of binding posts each, only single-wiring was possible; I used just one Ground Control per speaker, and none on the amplifier.

The simple playback system included a Denon preamp, an Edge Audio power amp, and a Marantz CD player. Interconnects were by Audio Magic, and speaker cables were relatively short, nonexotic, large-gauge stranded copper, by Tributaries. While the speaker maker was on a phone call, I had about 40 minutes to listen to tracks from Ry Cooder’s Jazz (CD, Warner Bros. 3197-2). My conclusions were the same as when I’d listened to the Ground Controls in my own system.

When the proprietor returned, he didn’t know if I’d installed the Ground Controls or not. He listened to a couple of tracks from Jazz, and his first comments were (I paraphrase) that the treble sounded slightly rolled off and the soundstage a little smaller than usual. Then, bent over the speakers with my back to him, I removed the Ground Controls. (He couldn’t see if I was installing them or removing them.) He listened to one of the tracks again and said that his speakers sounded as that model normally did.

In a second listening session, with the Ground Controls reinstalled but him still not knowing if they were in or out, he had the same impressions as the first time: The sound was different. He was convinced that the Ground Controls were now installed, and that the previous evaluation had been without Ground Controls.


There are many positive comments out there about AudioPrism’s Ground Controls, from reviewers and others who have already experienced them. My system, however, didn’t benefit from them, nor did a very different system. The Ground Controls indeed altered the sounds of both systems, but nothing I heard could be called a worthwhile improvement.

. . . Doug Blackburn

Associated Equipment 

  • Speakers -- Vandersteen 3A Signature, Vandersteen 2Wq subwoofers (2)
  • Preamplifier -- Belles/Power Modules 28A
  • Amplifier -- Belles/Power Modules 350A Reference, Jaton Operetta AV-AP2300AXU
  • Sources -- Modified Pioneer DV-525 DVD/CD transport; Perpetual Technologies P1-A/P3-A upconversion-dejitter-DAC combo w/Monolithic power supply; Roksan Xerxes turntable, rewired SME V tonearm, Cardas Heart low-output MC cartridge
  • Speaker cables -- Audience Au24e
  • Interconnects -- Audience Au24e, Nordost Quattro Fil
  • Power cords -- Audience powerChord e, Audience Au24e
  • Power conditioner -- ExactPower EP15A feeding an Audience aR6-TS
  • Computer (music playback) -- Toshiba Qosmio F45 Laptop running Windows 7
  • Headphones -- AKG K702

AudioPrism Ground Control Grounding Cables
Price: $149.99 USD per pair.
Warranty: One year parts and labor.

AP Labs, LLC
P.O. Box 24203
Seattle, WA 98124
Phone: (425) 922-2197

E-mail: info@audioprism.com
Website: www.audioprism.com