- John Siau
Many electronic products have a "CE" mark affixed to the product. This mark is mandatory in European markets, but is not required on products sold elsewhere. Few people understand what this mark means and why it is important. It is often a good idea to look for this mark when purchasing a product. It is also important to understand the differences between professional and consumer audio products (as defined in the CE standards).
- John Siau
This application note addresses these common questions and presents some guidelines for selecting headphones with the proper impedance and sensitivity.
- John Siau
High-Resolution Audio systems offer the promise of an extended high-frequency range. High-Resolution digital systems now operate at 2 to 4 times the sample rate of the standard CD. This means that these systems have the capability of extending the playback frequency range well above the 22 kHz limit of the standard CD. Does this added high-frequency range improve our listening experience? How high is high enough? Do we really need anything over 20 kHz?
- John Siau
There is a raging debate over the definition of "High-Resolution Audio". The focus of this debate has been misdirected by a lot of marketing hype. High-Resolution Audio will only truly arrive when the sum total of all defects in the audio chain become inaudible. We are not there yet, but we are getting close. The final chapter will not be higher sample rates and more bits. The final chapter will be achieving the necessary improvements to critical components in the signal chain.
If your playback system can't resolve anything better than CD quality, then "High-Resolution Audio" will remain an illusion.
- John Siau
It's all about control! - Headphone Output Impedance
The movement of headphone transducers must be well controlled in order to produce high-quality audio. It is easy to build a headphone amplifier that produces sound. It is an entirely different matter to produce an amplifier that is clear, clean, and enjoyable.
Headphone amplifiers need power and accuracy to achieve control. They also need to be protected from short circuits and overload conditions. The cheap, dirty, and common way to protect the amplifier is to add a series resistor between the amplifier and the headphone jack. This simple solution protects the amplifier from short circuits and overloads. Unfortunately, the resistor isolates the headphones from the amplifier, causing a loss of control. This ...
Headphones do not Behave Like a Resistor - Beware of Misleading Specifications!
A couple years ago, some of us at Benchmark noticed a weird discrepancy between our HPA2™ headphone amp (built into our DAC1 and DAC2) and some comparably-priced headphone amps. The advertised specifications of all the amps were basically the same, but they sounded noticeably different. Benchmark launched a detailed investigation to identify the differences. The results were surprising and are detailed in a white paper...
Recording Engineers and Audiophiles often distrust audio measurements and specifications. It is not uncommon to hear claims that a product measures poorly but sounds good. Occasionally we also hear claims that a product measures well but sounds bad.
This whitepaper documents significant differences between three headphone amplifiers that have nearly identical published specifications.
A playback system's volume control is often one of the weakest links in the audio chain. This is especially true when remote control is required.
Benchmark’s HDR-VC™ (High Dynamic Range Volume Control), combines the best features of two distinct volume control methods while adding remote volume control.
The circuits used to drive headphones are often added to a product without careful consideration of the difficult loads presented by high-quality headphones. The most common circuit is an opamp driver followed by a 30-Ohm series resistor. The series resistor provides short-circuit and overload protection while isolating the opamp from the inductance and capacitance of the headphones. The series resistor protects the opamp while keeping it stable. In contrast, today's state-of-the-art headphone amplifiers eliminate the series resistor, and use a high current driver. This change reduces distortion and flattens the frequency response when a headphone is driven. These new high-end designs are often called "0-Ohm" headphone amplifiers, and are ...
By Allen H. Burdick
This 24 page guide has been very popular. It has been hailed as “required reading for all broadcast engineers” by Richard Sequerra.
“We were able to change our engineering standards throughout the CBC as a result of this paper.” - Tom Holden Manager, Systems Engineering - Radio, CBC Toronto.
This paper revolutionized broadcast audio in the 1980's. It moved the industry away from 600-Ohm interfaces and radically changed the way analog audio was handled in professional environments.
In many ways, this paper still impacts every product that Benchmark builds today. We think that you will find this classic paper as useful today as it was when it was originally published in the 1980's. Due to the popularity of this paper, Allen updated it several times. The links will take you to Allen's final 1997 version.
We agree with Richard Sequerra: This is your required reading assignment!
By Allen H. Burdick
Two inexpensive jack-mounted products from Benchmark Media Systems can be assembled into a very powerful test set we call The Audio MicroScope™. The Audio MicroScope™ is a tool to be used in setting up analog audio systems. Because of its extremely high gain capability, over 85 dB, it is particularly useful in hunting down signal interface problems, such as hum and buzz from RF interference, magnetic induction, and ground loops.
By Allen H. Burdick
In the process of broadcast matrix encoding and decoding, balancing amplitudes between the two channels of a stereo audio path is very necessary. It is necessary for the maintenance of proper headroom, dynamic range and, of course, separation.
From time to time, repair and maintenance must be performed on equipment. Returning the entire chain to a balanced condition when placing the equipment back in service, is very desirable. Most broadcast engineers have balanced a chain at the stereo generator using the L-R method. But why not balance the output of each piece of equipment throughout the studio and eliminate the trip to the transmitter? It could mean eliminating late nights, and for those who don't go off the air, it may be the only option.
While recording studios do not face the same problems as the broadcaster, much of what is recorded in a studio is broadcast. This technique, therefore, is also applicable to the maintenance of a final stereo path in a recording facility.
By Allen H. Burdick
The high current output configuration of the HPA-1 is ideal for use as a transformerless long lines driver. Conversion of the unit for this purpose, source, transmission line, and termination considerations will be discussed.
Let's face it, an Audio Distribution Amplifier (DA) is not absolutely necessary for the distribution of audio! You can daisy chain your audio from input to input these days, generally with minimal loading on the source. However, what happens if a piece of equipment on the chain fails, or someone inadvertently cuts the audio pair, or you wish to remove a piece of equipment while on the air? Well, of course, that's why we install DAs in the first place. The DA is an insurance policy. But like any insurance policy, you'd better be sure of your coverage before you need to make a claim. To examine our insurance coverage, let's review the basic criteria for good audio transmission.
By Richard L. Hess, Audio-Video Systems Engineer, American Broadcasting Company, New York City
"The benefits of using a voltage audio transmission system in broadcast facilities is investigated. State of the art microphone preamplifier requirements and an ideal voltage system distribution amplifier are outlined. The application of the Peak Program Meter to the new systems and the modified installation at WABC-TV are covered."