Analog VU meters with bouncing needle displays have long been present on audiophile components, particularly amplifiers and tape decks. Think of the 1970s and 1980s vintage gear made by companies such as McIntosh, Audio Research, Luxman, Nagra, Phase Linear, and Accuphase. Simply stated, VU meters indicate the average level of an audio signal and provide an indication of perceived loudness. As McIntosh explains on its website, its familiar blue-paneled amplifier meters protect speakers from overload by “allow[ing] the monitoring of sound level balance and output level . . . .”
Interestingly, Pass Labs' founder, Nelson Pass, states that the needle display meters on his company’s amplifiers are different than most since they show the amp’s current consumption. According to Pass, since the electricity consumed by Pass Labs circuits is fairly high at all times, their meters never go to zero as do others.
The first VU meters, which borrowed the needle display from voltmeters, were the product of a joint effort by Bell Labs and the CBS and NBC broadcasting companies. Designed to adhere to the then popular “volume unit” standard, they were assigned the “VU” moniker. Cheap to manufacture, although often not extremely accurate, these meters were introduced in the US around 1939 to maintain proper levels during radio broadcasts and in early telephone systems. Even today, VU meters are extremely useful, if not essential, for professional recording applications as they can be used to avoid overloading, noise, and distortion.
But back to 1939. Due to the VU meter’s design limitations and disagreement concerning the technical underpinnings of the volume unit standard, BBC engineers across the pond quickly began referring to the VU meter as the “virtually useless” meter, instead preferring a much more complex meter developed a few years before the VU meter, called the peak program meter (PPM). Virtually useless meters are not to be confused with UI meters, which are jokingly referred to by many engineers as those that are “usually ignored.”
Like VU meters, PPM meters indicate the level of an audio signal. However, in simplistic terms, while a VU meter displays the audio signal’s average level, a PPM displays its peak volume. Suffice to say here that while both types of meters perform the same function, they do so very differently.
Beginning in the 1970s, VU meters from companies such as Sony, SAE (Scientific Audio Electronics), Yamaha, and Soundcraftsmen began using LED and plasma-based bars that move up and down or side-to side before at least temporarily retreating. Although those futuristic-looking meters show signal level in a different way than do needle displays, they express the exact same information.
Today, a growing number of VU audio meters, including ones used by companies such as Aurender and SAE, portray a digital rendering of an analog needle display. They exist only on an AMOLED or other type of display and disappear when the display is turned off.
That’s not to say that analog needle display VU meters have been abandoned. Quite to the contrary, Mcintosh, Audio Research, Luxman, Nagra, Accuphase, Yamaha, and many other manufacturers still prominently use them, with the most iconic perhaps being those found on McIntosh’s components. The analog VU meter needle displays on Dan D’Agostino Master Audio Systems components, aesthetically inspired by Breguet and Tourbillon watch faces, are arguably the most gorgeous.
There are other types of meters in home audio as well. In order to monitor tube bias, some components contain meters that indicate the DC balance status of the component’s output stage. Further, some power distributors and conditioners contain ammeters, which measure electrical current in amperes.
For those who find themselves sans meters, VU meter kits and finished ones, many freestanding and quite large, are widely available at places like eBay. While some of these aftermarket meters are classic in appearance, others are quite blingy. There are even downloads and mobile phone and desktop apps that can be used to turn a computer or phone display into a VU meter.
Although there seems to be widespread agreement that VU meters are essential on certain types of professional recording gear, their utility for home playback systems is, like a lot of audio topics, the subject of debate. Some audiophiles state that if you blow your speakers, the fact that VU meters simultaneously peak into the danger zone won’t provide you with much opportunity to turn things down.
Others agree with the statement on McIntosh’s website that, when monitored, VU meters are useful for monitoring purposes to help protect speakers from overload. They also state that ammeters are useful to determine whether an AC line is being overly taxed, thus alerting to the possible need of one or more additional lines. Of course, it can’t be disputed that presence of one or more meters seem to make an audio component come alive.
Despite any controversy, one thing is clear: the addition of meters on home audio playback gear can be good for business. As the head designer of one manufacturer recently told me, sales of one of his components increased exponentially after he added a meter. As a result, it’s safe to assume that for many audio companies, meters won’t be going anywhere soon. Long live the meter!
This article originally appeared in the Audio Classics newsletter and is used by permission. All photos courtesy of Howard Kneller.
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