Digital Audio Vu Meter Software
Introduction VU (Volume Unit) meters used to be the mainstay of audio metering systems, but they have been replaced by LED metering in a great many mixers and other applications. Even in software, the most common level meter is made to look like an LED meter, although there are quite a few 'analogue' software meters available as freeware. The Peak Programme Meter (PPM) was originally developed by the BBC to overcome the shortcomings of the VU meter, which is notoriously bad at showing the peak signal level. The VU meter is average reading, and the ballistics are important if an accurate reading is to be obtained. Ideally, a VU meter is supposed to take 300ms to stabilise, and should show only minor overshoot.
A volume unit (VU) meter or standard volume indicator (SVI) is a device displaying a representation of the signal level in audio equipment. The original design was proposed in the 1940 IRE paper, A New Standard Volume Indicator and Reference Level, written by experts from CBS, NBC, and Bell Telephone Laboratories. 'A unique audio meter and side chaining tool' - Blue Cat's Digital Peak Meter Pro (DPMP) is a unique audio analysis tool: it includes very flexible and customizable audio meters as well as advanced side chaining control capabilities thanks to its. VU meters are a measurement tool that shows the average level of an audio signal. You need VU meters for two big reasons. One, they hear loudness the same way our ears do, and two, they force you to put headroom in your mix. VU Audio Level Amp set VU meter Specifications: 500μA VU Meter with. Technical Pro PS9U Rack Mount Power Supply with 5V USB Charging Port. Meterk Digital Sound Level Meter, Range 30-130dB(A) Decibel Meter Noise Volume Measuring Max/Min/Hold Data Hold, Self-Calibrated Decibel Monitoring Tester(Battery Included). Aspen efd1000 pro installation manual.
Very few so-called VU meters come even close to the specification, and the little units on tape machines and sometimes provided on power amplifiers generally bear no resemblance to a real VU meter except that the meter dial is divided into the proper number of divisions, and has a red section from 0VU to +3VU. Oh yes, it will also say 'VU' on the meter face as well. PPMs are less common, although quite a few systems use LED arrays that are (more or less) PPMs.
Some show both VU and Peak Programme on the same LED array, with one LED seeming to 'stick' at a higher level indicating the peak. A true PPM has a linear scale and uses a logarithmic amplifier to convert the linear change of input voltage into a log output to drive the meter. See for an alternative to the system shown here. The later project relies on the meter's ballistics, but will be more than acceptable for most applications. Naturally, the two can be combined, but there is no PCB available for the circuit shown below. Description The unit described here makes no pretence at being a real VU meter, and although it can also be used as a PPM, it does not meet the original BBC standards, which call for a linear meter and a logarithmic amplifier, with highly specified ballistics. The term 'ballistics' refers to the absolute movement of the meter's pointer, and for true VU and PPMs there are detailed specifications for the movement of the meter needle in response to a signal. Benchmark detectives reading program programs.
PPM: A standard PPM has a 5ms integration time, so that only peaks wide enough to be audible are displayed. This translates into a response that is 1dB down from a steady state reading for a 10ms tone burst, 2dB down for a 5ms burst, and 4dB down for a 3 ms burst. These requirements are satisfied by an attack time constant of 1.7ms. The decay rate of 1.5 seconds to a -20dB level (IEC specified) is met using a 650 ms time constant. VU: A VU meter is designed to have a relatively slow response. It is driven from a full-wave averaging circuit defined to reach 99% full-scale deflection in 300ms and overshoot not less than 1% and not more than 1.5%. Since a VU meter is optimised for perceived loudness it is not a good indicator of peak (transient) performance.
Nominal sensitivity for 0VU is 1.228V RMS, and the impedance is 3.9k. Although these specifications are available as shown above, the meter movement itself will rarely behave itself well enough to meet the specs without a direct-coupled amplifier to control the meter's mechanical components. This would needlessly complicate the project, which needs to be able to indicate average and peak power or signal levels, but for the purposes of this exercise does not need the absolute accuracy of the real thing. Since properly damped meters are rare and expensive, I have chosen to use a standard readily available meter movement. This will be quite satisfactory for the intended purpose.
Analog Vu Meter
Free Vu Meter Software
The amplifier / rectifier is a simple LM1458 or similar dual opamp, and buffers the rectifier circuit. Active rectification is needed so the diode voltage drop does not cause huge inaccuracies, but by amplifying the signal first, we can use a simple rectifier and reduce the overall component count. The diodes must be germanium types as specified, or the low levels will suffer significant deviation from the ideal. Schottky diodes can be used if you can't get the germanium types (they are becoming hard to find) with a small loss of low-level accuracy. This is not intended as a precision instrument, but will be much better than the units that are available (OK; most of the units that are available - if you really want to spend $400 or more for a single meter, then it will be better than this - but by how much?). Figure 1 shows the typical internal circuit of simple (cheap) VU meters. A single diode is used in some, but the better ones will generally use a tiny selenium bridge rectifier or a germanium diode bridge.