CES 2013 Update

The 2013 International Consumer Electronics Show (CES) will be held from January 8–11, 2013, in Las Vegas, NV. (Now in its 45th year, the show debuted in June 1967 in New York, NY, with 200 exhibitors and 17,500 attendees.) The 2013 International CES, now considered the world’s most important consumer technology event, will feature product debuts from more than 3,000 exhibitors, covering more than 30 product areas, including the latest in content, wireless, digital imaging, mobile electronics, home theater, and audio, with a continued focus on electric vehicles and in-vehicle technology.

The Consumer Electronics Association (CEA), which sponsors the CES, recently announced it was awarded “The Most Innovative Organization” by Trade Show Executive magazine. The magazine also granted the International CES recognition as “The Most Innovative Green Initiatives by Show Management” for strides in “greening” at the 2012 International CES. Trade Show Executive’s 10th Annual Reader’s Choice Innovation Awards salute those who are making waves, from show managers to exhibitors, attendees, and the entire exposition industry. CES has earned top honors as the largest annual trade show since the Gold 100 Awards began four years ago.
Building on its green initiatives, the 2013 International CES will again feature the Sustainable Planet TechZone to showcase world-changing technologies that benefit the environment, utilize new sustainable energy forms, use smart grid technology, renew resources, and contribute to the global development. This exhibit area will feature products and services that make it possible for everyone to stay connected, informed, and live sustainable lifestyles. The GoElectricDrive TechZone will also highlight the latest technology behind electric vehicles for consumers seeking to live more sustainably through alternative transportation.

There will also be more than 200 conference sessions and more than 500 presenters anticipated to help educate attendees on the latest consumer electronic trends. This year’s CES is expected to be similar in size to last year’s show with about 150,000 people expected to attend. CES had 3,100 exhibitors in 2012, 2,700 in 2011, 2,500 in 2010, and 2,700 in 2009. With regard to attendees, CES had 156,153 in 2012, 141,000 in 2011, 120,000 in 2010, approximately 110,000 in 2009, and 141,150 in 2008.

The 2013 CES will be centralized at the Las Vegas Convention Center (LVCC) and the Las Vegas Hilton. The Venetian will still provide display space for high-performance audio.
Keynote speakers at this year’s show will include Gary Shapiro, CEA’s president and CEO; Kazuhiro Tsuga, Panasonic’s president; Lowell McAdam, Verizon’s chairman and CEO; Dr. Paul E. Jacobs, Qualcomm’s chairman and CEO; and Dr. Stephen Woo, president of Samsung Electronics Device Solutions.

A partial list of loudspeaker manufacturers and other relevant exhibitors includes: Acoustic Innovation, Adam Audio USA, Alpine Electronics, Amp of America, Anthony Gallo Acoustics, Aspersion, Arcam/Canton, Audio Engine, Bang & Loosen America, Bob Carver, Cadence Acoustics, California Audio Technologies, CDT Audio Stonewall, Crewing Vega Mobile, Clarion, Danville Signal Technology, Dayton Audio, dB Drag Racing Association, Devour Fidelity, Dyadic, Earthquake Sound, Edifier Enterprises Canada, Eggleston Works, Focus Audio, Genesis Advanced Technologies, Gibson Guitar, Golden Ear Technology, Harman, Harman Luxury Audio Group, Institute of Electrical and Electronic Engineers (IEEE), International Auto Sound Challenge Association (IASCA), Ion Audio, Jam, JBL Synthesis, Kenwood USA, Kicker, Kirsch Group, Krill, LA Audio Electronics, Lawrence Audio, LG, Line 6, Logitech, Loud Soft, Magic, Marten, Martin Logan, Massive Audio, Matrix Audio, MBL America, McIntosh Labs, Melon Industrial, Meridian American, Memphis Car Audio, Meridian America, Mite, Monster, Mordant-Short, Monitor Audio, Morel, Motes Audio, Maim Audio, Nola Speakers, Only USA, Opera Loudspeakers, Orca Electronics/Focal America, Paradigm Electronics, Parasound, Peachtree Audio, Peerless Fabrikkerne (India), Pioneer Electronics/TAD, PMC, Polk Audio, PowerBass USA, Prism Sound, PSB Speakers, Pure Acoustics, Pyle Audio, Raidho Acoustics, RBH Sound, Rel Acoustics, Revel, Rives Audio, Russound, Samson Technologies, Samsung, Shanghai Silver Flute, Sonos, Sony, Soundmatters, Tannoy, Thiel Audio, THX, Tivoli Audio, Totem Acoustics, Usher Audio, Vandersteen Audio, Velodyne Acoustics, Vienna Acoustics, Voxx International, Waterfall Audio, WBT USA, Westlake Audio, Wharfedale, Wilson Audio, Wisdom Audio, YG Acoustics, and Zimri Speakers. Visit www.cesweb.com for more information.

December Products: Ultra Loudspeakers, GAGA Tube Guitar Amp, & More

The December 2012 issue of audioXpress features product information about a variety of must-have audio gear. Headphones, an amp, a mic, and more are detailed.

SVS Introduces New Ultra Series

SVS recently launched its Ultra series of full-range loudspeakers. The speakers are designed to deliver uncompromised audio performance, boast unsurpassed build quality, and cost-is-no-object performance at an affordable price.

SVS Ultra

The SVS Ultra series loudspeakers were designed by audio enthusiasts with more than 50 years combined experience in the high-end audio arena. The result is a loudspeaker that convincingly conveys the emotion of live music and home theater. The SVS Ultra series delivers a deep, detailed soundstage with incredible resolution, absolute transparency, and rich and articulated bass.

The lineup includes a 45″-tall upswept trapezoidal tower, a bookshelf speaker, a center channel, and a surround speaker. The result is a performance level even more expensive loudspeakers cannot match.

Every other speaker in the Ultra series has been designed to complement the Ultra Tower’s performance, with flush-mounted drivers to reduce diffraction and improve on-axis, high-frequency response, along with rear-mounted bass reflex ports (on the Tower, Bookshelf, and Center speakers) for phenomenal bass output and extension and minimal frequency response degradation.

New Tube Guitar Amp

Milbert Amplifiers introduces the GAGA D-30 tube guitar amplifier, the third in its line of Guitar Artists’s guitar amplifiers. Based on the revolutionary GAGA 90 and offering similar features and functions, the “domestic” model GAGA D-30 provides from 1 W up to 30 W of full-power audio output, is 11 lb total weight, and offers 120-V/240-V mains input.

Milbert GAGA D-30 tube guitar amplifier

The GAGA D-30 may be upgraded to either the domestic GAGA D-60 model, or to the international GAGA 90 model. The upgradeable nature of GAGA amplifiers extends its versatility.

Features common to GAGA amplifiers include: patented technologies; no traditional audio output transformer; light-weight, high-power capability; the ability to play more than 30 kinds of tubes in unlimited combinations, for tonal versatility; adjustable headroom for more distortion at low volumes (down to 1 W); Auto-Everything that auto-biases all tubes; Auto-Impedance and Blow-Proof universal speaker outputs; advanced, regulated power supplies; extended tube lifetimes and Auto-Standby; P3-Ready 9-V high-current phantom power for pedals and active pickups; upgradeability throughout the amplifier series; and it’s made in U.S.

Image ONE Series Gains Bluetooth Model & Product Upgrades

Klipsch now offers its new Image ONE Bluetooth and an upgraded Image ONE. Catering to on-ear enthusiasts, these headphones maintain the same high-quality sound signature and comfort while introducing enhancements in build, functionality, design, and performance. With the launch of these two Image ONE series models, Klipsch introduces upgraded, flat cabling (attached only to the left ear cup) for added durability and tangle resistance, and a flat-folding, collapsible design.

Klipsch Image ONE

The Image ONE Bluetooth serves as Klipsch’s first wireless headphone model. Given its utilization of Hi-Fi Bluetooth (A2DP) audio quality and aptX Codec for lossless streaming, users experience high-performance, uninterrupted listening. The Image ONE Bluetooth’s wireless capabilities are enabled via its built-in rechargeable battery, with wired connection still possible via the included direct-connect audio cable. Large, easily-accessible controls are located on the right ear cup for controlling playlists and phone calls.

Maintaining the same acoustics of the current model, the updated Image ONE provides listeners with flat earpads and an adjustable leather headband for optimal comfort and fit, still providing superior levels of noise isolation. Simplifying cable design, the headphone utilizes only one cable that feeds into the left ear cup. Because the headphone’s ear cups fold flat into the headphone, a smaller carrying case is provided for more compact storage. The same three-button remote and mic is housed on the cable for full call and music control with Apple devices.



Q&A: Andrew Spitz (Sound + Interaction Designer)

Andrew Spitz is a Copenhagen, Denmark-based sound designer, interaction designer, programmer, and blogger studying toward a Master’s interaction design at the Copenhagen Institute of Interaction Design (CIID). Among his various innovative projects is the Arduino-based Skube music player, which is an innovative design that enables users to find and share music.

The Arduino-based Skube

Spitz worked on the design with Andrew Nip, Ruben van der Vleuten, and Malthe Borch. Check out the video to see the Skube in action.

On his blog SoundPlusDesign.com, Spitz writes:

It is a fully working prototype through the combination of using ArduinoMax/MSP and an XBee wireless network. We access the Last.fm API to populate the Skube with tracks and scrobble, and using their algorithms to find similar music when in Discover mode.

The following is an abridged  version of an interview that appears in the December 2012 issue of audioXpress magazine.

SHANNON BECKER: Tell us a little about your background and where you live.

Andrew Spitz: I’m half French, half South African. I grew up in France, but my parents are South African so when I was 17, I moved to South Africa. Last year, I decided to go back to school, and I’m now based in Copenhagen, Denmark where I’m earning a master’s degree at the Copenhagen Institute of Interaction Design (CID).

SHANNON: How did you become interested in sound design? Tell us about some of your initial projects.

Andrew: From the age of 16, I was a skydiving cameraman and I was obsessed with filming. So when it was time to do my undergraduate work, I decided to study film. I went to film school thinking that I would be doing cinematography, but I’m color blind and it turned out to be a bigger problem than I had hoped. At the same time, we had a lecturer in sound design named Jahn Beukes who was incredibly inspiring, and I discovered a passion for sound that has stayed with me.

Shannon: What do your interaction design studies at CIID entail? What do you plan to do with the additional education?

Andrew: CIID is focused on a user-centered approach to design, which involves finding intuitive solutions for products, software, and services using mostly technology as our medium. What this means in reality is that we spend a lot of time playing, hacking, prototyping, and basically building interactive things and experiences of some sort.

I’ve really committed to the shift from sound design to interaction design and it’s now my main focus. That said, I feel like I look at design from the lens of a sound designer as this is my background and what has formed me. Many designers around me are very visual, and I feel like my background gives me not only a different approach to the work but also enables me to see opportunities using sound as the catalyst for interactive experiences. Lots of my recent projects have been set in the intersection among technology, sound, and people.

SHANNON: You have worked as a sound effects recordist and editor, location recordist and sound designer for commercials, feature films, and documentaries. Tell us about some of these experiences?

ANDREW: I love all aspects of sound for different reasons. Because I do a lot of things and don’t focus on one, I end up having more of a general set of skills than going deep with one—this fits my personality very well. By doing different jobs within sound, I was able to have lots of different experiences, which I loved! nLocation recording enabled me to see really interesting things—from blowing up armored vehicles with rocket-propelled grenades (RPGs) to interviewing famous artists and presidents. And, documentaries enabled me to travel to amazing places such as Rwanda, Liberia, Mexico, and Nigeria. As a sound effects recordist on Jock of the Bushvelt, a 3-D animation, I recorded animals such as lions, baboons, and leopards in the South African bush. With Bakgat 2, I spent my time recording and editing rugby sounds to create a sound effects library. This time in my life has been a huge highlight, but I couldn’t see myself doing this forever. I love technology and design, which is why I made the move...

SHANNON: Where did the idea for Skube originate?

Andrew: Skube came out of the Tangible User Interface (TUI) class at CIID where we were tasked to rethink audio in the home context. So understanding how and where people share music was the jumping-off point for creating Skube.

We realized that as we move more toward a digital and online music listening experience, current portable music players are not adapted for this environment. Sharing music in communal spaces is neither convenient nor easy, especially when we all have such different taste in music.

The result of our exploration was Skube. It is a music player that enables you to discover and share music and facilitates the decision process of picking tracks when in a communal setting.

audioXpress is an Elektor International Media publication.

AX December: Speaker Design, Interactive Sound, Power, & More

audioXpress is all about range—range, in the sense of content diversity. Our international team publishes insightful articles on a wide variety of topics such as speaker design, sound analysis, glass audio projects, and hi-fi product reviews. This month we deliver once again.

First, I suggest you check out the interview with innovative sound designer Andrew Spitz (p. 38). Much of his current work focuses on “interactive experiences.”

Interested in speaker design? We’ve got you covered. Consider starting with the first part of Richard Honeycutt’s series, “Speaker Design School.”

Then  turn to page 8 for the second part of the series “Ribbon and Planar Magnetic Loudspeakers.” Finally, flip to page 14 for the conclusion to Ton Giesberts’s series on his active loudspeaker system project.

The completed PCB for the subwoofer is attached to its heatsink

Ready for a comprehensive transducer test? You can always rely on Vance Dickason’s expert analysis. This month he presents the results of tests he ran on a Morel TiCW 634Nd (p. 30).

The Morel TiCW 634Nd

Once you’ve had your fill of speaker articles, read what Gary Galo thinks about remastered editions of David Hancock’s 1967 recording of the Dallas Symphony’s presentation of Rachmaninoff’s Symphonic Dances (p. 24). What would you choose: vinyl, digital, or both?

If you’re a glass audio enthusiast, head to page 35 to refresh your understanding of power supplies for hollow-state electronics. Transformers and rectifiers are covered in detail.
Lastly, note that the long-awaited amp test page referenced in Richard Honeycutt’s audioXpress November 2012 article—“Differences in Amp Sound: What’s the Truth?”—is now available at www.edcsound.com/amptest.htm.

November Products: Cush Headphones, Measurement Mics, & More

The November 2012 issue of audioXpress features product information about a variety of interesting, well-designed audio gear. Headphones, an amp, a mic, and more are detailed.

Cush Headphones Offer Sound Quality, Comfort, & Style

KICKER recently unleashed its 39 years of high-performance audio knowledge to offer KICKER Cush headphones.

KICKER’s Cush (Source: KICKER)

Featuring an ultra-lightweight design and thick over-the-ear cushions, Cush headphones offer 54-mm speakers and a 118-dB maximum output to provide the legendary bass response and tonal accuracy for which KICKER is known.

The headphones feature a smooth, soft-touch finish in black gloss or white with monochromatic graphics for a subtle appearance. The breathable, perforated headband cushions the listener’s head.

Cush headphones utilize a 53”, Kevlar-reinforced, flat cable to provide freedom for movement while listening. The flat cable is smooth and less prone to tangles. The angled “L” plug connects into any iPod, iPhone, MP3 player, or KICKER docking system.

Barix Expands Audio Product Range

Barix markets its Annuncicom IP audio and SIP/VoIP devices around the world, bringing bidirectional audio streaming and control solutions to various markets within the commercial, entertainment, private sector, and residential worlds.

Barix’s Annuncicom 60 (Source: Barix)

Barix now offers two low-cost, reliable VoIP and IP Annuncicom audio devices that optimize features and functionality for universal applications.

The new Annuncicom 50 is built specifically for OEM applications. The device delivers Barix’s trademark reliability, open standards design, and multi-format audio capability at a low cost for OEM customers.

Barix also offers the Annuncicom 60, a universal, programmable, and ultra-compact device that offers reliable IP encoding and decoding. It is roughly 40% the size of existing Annuncicom devices, which are known for offering a compact footprint to systems integrators and end users.

The Annuncicom 60 is a single-zone paging interface device that can decode VoIP codecs as well as MP3, AACplus, and PCM audio. Its built-in speaker amplifier, balanced line output and microphone interfaces, serial and contact closure control interfaces, and Power over Ethernet (PoE) support is unique to the market—delivering universal functionality at a competitive price.

Contact Barix for more information at www.barix.com or www.ip-audio.info.

Sennheiser Offers High-End Amp & Headphones

Sennheiser now offers an amplifier for dynamic headphones. The digital HDVD 800 has a fully symmetrical layout and sampling frequencies of up to 24 bit/192 kHz to ensure an unequalled listening experience. It also harmonizes perfectly with Sennheiser’s HD 800, HD 700, HD 650, and HD 600 high-end headphones.

Sennheiser’s HDVD 800 (Source: Sennheiser)

The HDVD 800’s features include its balanced sound image, maximum precision, and impressive spatiality. The high-end headphone amplifier has a fully symmetrical layout for operation with analog audio sources, ensuring symmetrical signal transmission from the source to the headphones. For use with digital sources, the amplifier is equipped with a high-quality Burr-Brown digital/analog converter that converts digital audio data into analog signals, enabling the HDVD 800 to transmit the entire frequency spectrum of high-end audio sources without any frequency loss.

A rotary gain switch at the rear of the unit provides simple adaptation of the amplifier output to the audio input voltage. This ensures that the dynamic range can be used to its full extent.

The HDVD was developed and designed in Germany, which is where the latest member of Sennheiser’s high-end series is also being manufactured.

Sennheiser also offers the IE 800 in-ear earphones, which the company describes as headphones with “the most innovations per square millimeter.”

Sennheiser’s IE 800 (Source: Sennheiser)

The IE 800 offers innovative technology providing brilliant trebles, precise bass response, and a detailed, lifelike sound image with a 5-to-46,500-Hz frequency response.

The IE 800’s interior conceals many small but effective innovations: the centerpiece is Sennheiser’s specially developed extra wide band (XWB) driver. With a 7-mm diameter, it is the smallest wide-band sound transducer available in dynamic headphones. Its functional principle guarantees distortion-free sound even at high-sound pressure levels. It also features a modern design and high-quality materials (e.g., scratch-resistant ceramic housing).

Pro V-Series Speakers Provide High Sonic Accuracy

Pro Audio Technology (PRO), a leader in professional-grade loudspeaker and digital amplifier technology, announced the new V-Series loudspeakers, designed to deliver the high-impact dynamics for which PRO is known, but at a more affordable price. Both new models, the SCRS-210v full-range loudspeaker and the LFC-12v subwoofer, feature 6” enclosures, placing high-output systems in small rooms.

The SCRS-210v loudspeaker (Source: Pro Audio Technology)

The SCRS-210v’s two 10″ woofers provide a high-sound pressure of 102 dB with 1 W of input and combined, can handle 300 W of continuous power. Offering even higher sensitivity, the 1” annular-diaphragm compression driver produces 110 dB/W and delivers detailed and extended highs. Striking a balance of power and accuracy, the SCRS-210v fills nearly any space with cinema-quality sound and concert-caliber music without industrial-grade pricing or space requirements.

For low-frequency support, the companion LFC-12v subwoofer features a high-output 12″ professional-grade woofer with a 4″ voice coil. With sensitivity rated at 96 dB driven with 1 W, and power handling up to 700 W, the LFC-12v has no problem with today’s high-quality recordings.

When paired with the PMA amplifier/processor, advanced digital EQ can be applied to compensate for speaker positions near boundaries or for the effects of placement behind viewing screens or fabric. The PRO V-Series loudspeakers and PMA amplifiers provide a level of sonic accuracy unparalleled at the price.

Acoustic Measurement Microphones

PCB Piezotronics, a leader in the design and manufacture of microphones, vibration, force, torque, load, strain, and pressure sensors, and the pioneer of ICP technology, now offers a 0.25” prepolarized microphone series to complement its line of acoustic products. Models 378C01 and 378C10 are microphone and pre-amplifier combinations designed to measure high frequencies and high amplitudes. The distinguishing features for this series are the microphone frequency capability, which can accurately measure up to 100 kHz, and the 165-dB amplitude range (i.e., 3% distortion limit).

PCB’s Model 378C01 free-field microphone (Source: PCB Piezotronics)

Model 378C01 is a free-field microphone and pre-amplifier suitable for automotive and aerospace noise source location and array applications. Other common applications include biological and medical acoustic analysis, machine monitoring and defect detection, gunshot analysis, cabin noise, and other applications (e.g., testing in anechoic chambers). Model 378C10 is a pressure response microphone typically used in noise absorption applications within impedance tubes or general noise testing in cavities or small enclosures.

PCB carries a full line of prepolarized condenser microphones and pre-amplifiers. The prepolarized designs can also be used with the same constant current source used for ICP accelerometers, minimizing set-up time. PCB also offers the traditional externally polarized microphones that operate from a 200-V power supply.

Differences in Amp Sound: What’s the Truth?

Back in the 1960s, after crossover distortion was tamed in the better solid-state amplifiers, many serious audiophiles remained convinced that tube amps sounded better than any solid-state ones. Then in the 1970s, after Matti Otala and others had demonstrated the effects, cause, and prevention of slewing-induced distortion, the percentage of serious audiophiles who preferred tube amps may have declined slightly, but it certainly did not drop to zero.


The first tests to determine the cause of the difference in sound, if any, were mostly performed by engineers, who concluded that since the frequency response and distortion performance of the best tube and the best solid-state amplifiers were comparable, there must not be any difference (see Photo 1). Thus began the so-called “Great Debate.” I believe we are now in a position to put this debate to rest.

Photo 1: Tubes or transistors? A listener’s preference is a subjective choice.

First, I must affirm, as mentioned in a previous article, that subjective amplifier judgments are, by nature, individual perceptions. Every perception is a fact to the person perceiving. Thus, if you tell me you can hear a difference between two amplifiers, I have to believe you. If I can hear no difference, then perhaps you are a more critical listener than I am. If neither I nor any of a dozen other skilled listeners can hear a difference, then you have indeed heard a subjective difference, but since the perceived difference is not a shared reality, we cannot say there is an objective difference. If you cannot prove in a properly designed double-blind test that you can repeatedly hear a difference, then we must conclude that the difference you do hear does not proceed from physical, and therefore, determinable, causes.


In last month’s article, I discussed blind and double-blind testing. Both assume that the equipment under test is presented in a pair: two amplifiers or two speakers and so forth are being compared. In a blind amplifier test, the test subject (i.e., the person providing opinions about the equipment under test) does not know which amplifier is playing at a given time, in order to avoid the effects of extraneous variables (e.g., manufacturer preferences or finish details). Long ago, experimenters found that test operators (e.g., set-up technicians or other persons involved with the experiment) would sometimes unintentionally provide clues via facial expression or body language that could give away the identity of the equipment under test. Thus, double-blind tests, in which no one involved in the test operation knows which piece of equipment is being used at a given time, were developed. Double-blind tests are the gold standard for any tests involving human perception.

Some people do not like double-blind tests, believing themselves to be immune to hidden biases. However, there is no evidence to prove that even the best of intentions enable a person to avoid subconsciously tilting his/her test responses in a preferred direction. (Perhaps a Vulcan could?)

Resistance to double-blind testing is not limited to those who believe tube amplifiers sound better, although some of those listeners still offer objections to the elaborate test protocols. Some people firmly believe that any well-designed IC-based amplifier sounds better than any hollow-state amplifier and still claim that double-blind testing is unnecessary for them. Perhaps the most convincing for me personally was an individual who told me he made a change that was expected to make an amplifier sound better, but he was surprised to find that it sounded worse. No details of the test protocol were given. Of course, this amounts to hearsay, and thus cannot be considered scientific evidence.


In 1977, the British magazine Hi-Fi News and Record Review published an article by Jean Hiraga detailing sensitive distortion measurements made in Japan on a variety of tube and solid-state amplifiers that operated well below clipping. The article was reprinted by audioXpress in the March, 2004 issue. This article showed conclusively that differences in the distortion spectra of excellent amplifiers do exist, but no effort was made to correlate these measured differences with perception.

In the March, 1980 issue of High Fidelity magazine, “The Great Ego-Crunchers: Equalized Double-Blind Tests” by Daniel Shanefield was published. This article directly addressed the perception issue. Shanefield mentions the division of audiophiles into “golden ears” who insisted that they could hear differences in amplifiers and “nonbelievers,” who constitute the majority. He makes the statement: “In the next few years (after 1970) several small-circulation magazines espoused the golden-ear point of view, though they often disagreed with each other about which components were truly excellent and even changed their minds drastically from issue to issue.” Shanefield’s conclusion was that audible differences among good-to-excellent amplifiers do indeed exist, but that if the frequency response of all amplifiers under test was equalized to be flat within 0.25 dB, no perceptible difference remained. He includes the somewhat startling detail that when he compared three Dynaco 400 samples, frequency response differences of a few tenths of a decibel did exist, and the amplifiers did sound different. His experimental protocol ensured that the amplifiers were operated well below clipping. Shanefield’s tests were subsequently replicated by several members of the Boston Audio Society.


In October 1991, David Clark of DLC Design presented the paper, “Ten Years of A/B/X Testing” at the 91st Convention of the Audio Engineering Society. A/B/X amplifier tests compare an unknown amplifier “X” with two known amplifiers, “A” and “B.” The test subject’s goal is to determine whether “X” is “A” or “B.” For example, an excellent amplifier can be used as “A,” and a medium-grade amplifier as “B.” The test subject can switch at will among “A,” “B,” and “X,” but the switches may be connected so that position “X” is actually amplifier “A” (see Photo 2). If the subject can reliably identify “A” is “X,” then clearly the difference between “A” and “B” is perceptible to him. If not, we cannot conclude that there are physical causes for the differences that some listeners perceive under less-controlled conditions.

Photo 2: A flick of the switch enables test subjects to switch amplifiers. Sometimes “X” was the same amplifier as “A” or “B.”

A/B/X tests are usually double blind, but they do not require the equipment’s brand/model under test be kept from the listeners, since neither the listener nor the test operator knows which is “A,” “B,” or “X.” Test subjects are not permitted to communicate with each other.

In an A/B/X test, the listener chooses when to flip the switch, allowing whatever amount of time he feels is needed to properly identify the unit under test as “A” or “B.” A test may span several listening sessions, if the listener so chooses, or may be finished quickly if the listener is confident he has determined the identity of “A” or “B” as “X” in a short time.

A/B/X testing excels at finding perceptible differences, if any exist, but is not designed to establish levels of accuracy or preferability. The A/B/X test itself was compared with long-term listening as a method of identifying a calibrated 2.5% total harmonic distortion (THD) component that was added to a musical signal. The Audiophile Society acted as the “golden ears.” The Southwestern Michigan Woofer and Tweeter Marching Society (SMWTMS) acted as the “engineers.” Neither group could identify the distortion at a 5% confidence level in long-term listening tests. However, using A/B/X testing, the SMWTMS not only correctly proved the audibility of the distortion in 45 min. of testing, but also correctly identified a lower amount of distortion. In the complete series of tests, THD was found to be audible at 4% using big-band jazz music, 2% using flute music, and 0.4% using a sine wave. The spectrum of the harmonic distortion was not specified in Clark’s AES paper (AES Preprint 3167).

Clark added a note in his 1991 paper, based on a private conversation with Thomlinson Holman (the “TH” of THX). Holman has found that a number of professional power amplifiers do distort audibly when driving highly reactive loads (e.g., some theater speakers) when playing explosive movie sounds. The cause could well be that under such severe load conditions, the amps’ power supplies experience instantaneous drops in voltage. This condition would be easy to identify using an oscilloscope.


Audio professional Richard Clark (note: this is a different Clark), originally a believer that different amplifiers sound different, set up a $10,000 challenge: anyone who, by listening only, can identify which of two amplifiers is which, under rules he has established, will receive the prize. The rules can be found at http://tom-morrow-land.com/tests/ampchall/rcrules.htm. They primarily include minimum-quality levels for participating amplifiers, level matching, and so forth, all of which are essential to the validity of any comparative test.

In the years since the challenge was first offered, most large groups have obtained accuracy  of  49–51%, which are essentially the results one would expect to occur by chance. Smaller groups have never gotten more than 60% correct. In any statistical sampling, small test groups are more likely to deviate from chance results. As the test population is increased, test results converge toward a specific value. For a random process, a larger test population is likely to converge toward chance results. The fact that Clark found more nearly chance results when measuring larger groups is itself a strong indicator the test subjects’ responses were random, not ordered as would be the case if there were perceptible differences between the amplifiers being tested. These are averaged scores for the groups. No individual has ever reached 65% correct. These results do not permit us to say no person can ever hear differences between two good amplifiers, but they do strongly indicate that any such differences must not be very robust (see Photo 3).

Photo 3: Listeners must often determine for themselves what they hear (e.g., if this sound plotted here is actually clipping on transients).

No test such as David Clark’s or Richard Clark’s can ever show that there are no perceptible differences in amplifier sound. Proving the non-existence of anything is philosophically problematic because we can truthfully say only that any experiment did not find such-and-such a thing. However, we cannot perform all possible experiments. As an analogy, we cannot say there are no white crows, because we cannot look everywhere at once. If we postulate the nonexistence of white crows, the person who finds a single example will prove us wrong. So far, however, no person has demonstrated publicly in a scientific fashion that he can reliably distinguish between the sound of two good amplifiers with identical frequency response and low noise driven below clipping. And yet the perception remains that there are real differences in amp sound. As a consultant in acoustics and sound/video system design, I regularly encounter people who assume I must have a vacuum-tube stereo system “because everyone knows they’re better.”

It is true that almost all tube power amplifiers have a very slight high-frequency rolloff (tenths of a dB), but no test has convincingly shown that such a small deviation from flat is perceptible (see Photo 4). (If it is, and makes the sound better, should we all add inexpensive RC low-pass filters to our amplifiers to improve the sound so they sound like tube amps?)

Photo 4: One factor could be whether or not the output transformer affects the sound.


There are still serious researchers who are trying to find the elusive ingredient to tube sound. In October, 2011, Shengchao Li of Potomac, MD, presented a paper, “Why Tube Amps Have Fat Sound While Solid-State Amplifiers Don’t,” to the Audio Engineering Society’s 131st convention in New York. The paper was reviewed by two qualified anonymous reviewers. Li begins from the assumption that tube amps do indeed sound different. He proceeds to explain that the differences arise from output-tube nonlinearities, amplifier output impedance, and output-transformer nonlinearity resulting from the core material’s B-H curve. These nonlinearities, Li says, interact to reduce the low-frequency output of the amplifier under some conditions. The speakers, whose nonlinearity is worst at low frequencies, thus have less signal at those frequencies and thus produce less distortion. In this manner, some low-frequency output is traded for reduced low-frequency distortion. The first two mechanisms suggested by Li have been discussed in earlier Hollow-State columns. The third may be significant in low-feedback amplifier designs, but in more typical Williamson designs, transformer nonlinearities are largely compensated by negative feedback. Certainly all three mechanisms will be exacerbated at levels approaching or exceeding clipping. It would be instructive to see if a low-feedback tube amplifier could be identified in A/B/X testing, and just what level of overdriving is necessary to permit objective identification of any amplifier.


Let us now step bravely into the hornets’ nest. After four decades of testing by a number of very capable scientists, no evidence has been published that shows any objective difference among the sound of good-to-excellent audio amplifiers operated well below clipping, if the frequency responses are equalized within 0.25 dB of flat. Does this indicate there is no “tube sound”? It does not, for several reasons.

First, almost no home-music listener (or even recording studio engineer) equalizes the amplifiers flat within 0.25 dB. Virtually no speaker pairs are matched that closely all across the passband. And a flat response is not always everyone’s first choice. Hi-Fi systems of the 1950s usually had “scratch” and “rumble” filters to remove the sound of artifacts on vinyl recordings. These typically applied a 3-dB/octave high cut  above 8 kHz, and low cut below 80 Hz, respectively. Presumably they were included because equipment manufacturers found that their customers wanted and used them: at least under some conditions, listeners did not prefer flat response.

Second, a significant number of audio amplifiers are made for instrument amplification. The distortion used intentionally with electric guitars is well-known. I have also played with professional keyboardists who preferred tube-type Hammond organs because of the “growl” they produce at high volumes. This growl comes from distortion—largely intermodulation distortion—in the tube power amplifiers. A smaller percentage of audio listeners, but still a non-negligible number, prefer some distortion even in their music reproduced from recordings. Naturally, the distortion spectrum  is quite important to such people. As shown in a previous column and in Hiraga’s 1977 tests, that spectrum is very different for a tube amplifier versus a solid-state amplifier. It is a safe generalization to say that most people prefer tube distortion over the distortion of a solid-state amplifier. Most probably prefer triode tube distortion specifically.

Third, there are conditions under which distortion, even if not desired, occurs in an audio chain. It can happen when a person is listening to music at high levels, especially if low-efficiency speakers and/or underpowered amplifiers are being used. I believe this occurrence is the rule rather than the exception for many serious music listeners. Not only rock music, but also symphonic music, pipe organ music, and big-band jazz require a lot of amplifier power in order to play through typical home-stereo speakers at realistic levels without clipping. Aside from amplifiers for music listening, another place where “tube sound” is much hyped is in microphone preamps for audio recording. In this application, it is not uncommon for the microphone to put out surprisingly high voltages. Capacitor microphone cartridges, especially, are almost immune to clipping, so when exposed to high sound pressures, they can produce output voltages close to 1,000 times their normal output levels. Under these conditions, preamp clipping is pretty much inevitable. Again, the distortion spectrum is very important, and most recording engineers prefer the spectrum provided by tube pre-amps.

So in this columnist’s codgerly opinion, there is indeed a “tube sound” under some conditions, and many excellent technicians, engineers, and audiophiles find it preferable for specific applications. It is not, however, scientifically accurate to claim that hollow-state amplifiers are better or worse than—or even perceptibly different from—solid-state ones for all applications.

Purely audio considerations aside, many audiophiles prefer the aesthetics of a “warm,” artistically designed (perhaps handcrafted) amplifier over the usual “high-tech” appearance of most solid-state amplifiers. And many of us enjoy the “legacy” feel of the equipment setup when operating vacuum tubes are visible. These are valid reasons to buy hollow-state equipment, if it appeals to you.


If you are still not satisfied about the topic of “tube sound,” you are invited to take part in an online test. The test has two parts. In the first part, you will be invited to use quality headphones (please, not computer speakers) to listen to a pair of .wav files of a short clip played by the lead guitarist of Darrell Harwood and the Coolwater Band. One file was made by recording directly to digital from the guitar, then playing the recording through a solid-state power amplifier adjusted to produce an acceptable amount of distortion for proper artistic effect. The other file uses the same digital recording, played through a tube amplifier adjusted in the same way. Both recordings were made using the same speaker and cabinet, and were recorded using a type 1 calibrated measurement microphone with a tensioned stainless steel diaphragm. The same physical setup was used for both recordings, and the levels of the recordings were carefully matched. You may play the files as many times as you wish, and will then be requested to send an e-mail stating which file, “A” or “B,” sounded better to you. If you choose to include your opinion as to which is the tube-amp and which is solid-state recording, please do that as well. The purpose of this part of the test is to illustrate the sound of the different distortion spectra of tube versus solid-state amplifiers.

The second part of the test consists of three .wav recordings of a brief clip of classical music. There is a reference clip made directly from the CD, a clip of the selection being played through a McIntosh hollow state power amplifier, and a clip of the selection being played through a commercial solid-state power amplifier.  Both of the “amplifier” recordings were made using an Evenstar Pro Peregrin studio monitor speaker, recorded using the measurement microphone described above, with the same physical setup. No equalization was applied to either amplifier, and the amplifiers were operated well below clipping. The reference (“X”) straight-through recording is identified, and you are asked to listen to the “A” and “B” recordings, determine which sounds more like the reference, and e-mail your results. The test can be found online at www.edcsound.com/amptest. It will be available until the end of 2012. Instructions for participating are included on the website.