![]() ![]() PPM meters are good for peak detections while recording, like snare drum hits which are short transients. PPM meters have a rise time of 10ms and a fall time of 24dB in 2.8 seconds. ![]() Somebody up there was talking about PPM meters, which preceded VU meters in the invention timeline. This is called meter ballistics and there are a few standards and propriatary ones out there aside from VU. The fall time is the same value of 300ms from the removal of the signal (0 VRMS) from 0VU to the gauge stop. The 300ms rise time is defined as: Rising from no signal to 99% of “0 VU” when a 1.228 VRMS 1 kHz sine wave tone is applied across a 600-ohm load for 300 milliseconds. 0VU equals +4 dBu, or 1.228 volts RMS, a power of about 2.5 milliwatts when applied across a 600-ohm load. Overshoot is to be less than 1 to 1.5% of scale. The specification for physical VU meters is a 300ms rise and fall time. I have a soft spot for VU meters and have a drawerful. No forgiving saturation there! So peak metering is essential for digital recording… and that’s why you seldom see VU meters any more, kids. So the best you can hope for is to find a consistent average level that uses the tape’s dynamic range with the minimum of peaks running into the saturation area.ĭigital recording, on the other hand has an absolute, rock hard maximum level point beyond which the signal is clipped hard. This point is dependent on tape used, head gap, bias frequency and level, and even the spectral makeup of the recorded sound. VU meters were also ok for recording to magnetic tape, because analog recording to tape does not have a hard upper limit, just a point before which saturation starts happening. You want the listener to get a consistent apparent level, song to ad to news to song etc. VU meters indicate the average level of audio programming and they were ideal when you wanted to keep an eye on loudness, which is paramount for broadcasting. Posted in Microcontrollers, Software Hacks Tagged oled, physics, VU meter Post navigation We know it will take more than a few wiggling pixels to pry real analog indicators out of some hacker’s tool boxes, but anything that helps improve the digital approximation of this sort of vintage hardware is a win in our book. Unfortunately there’s no code for you to play with right now, but says he’ll release it on the project’s Hackaday.IO page once he’s cleaned things up a bit. Obviously it’s something that can only be appreciated in motion, so check out the video below for an up-close look at his quasi-retro indicator. So he’s been experimenting with adding some physics to the meter’s virtual needle to better approximate the distinctive lag and overshoot that’s part and parcel of analog indicators. liked the idea, but thought it was a tad too stiff. It was cheap and easy to implement, and promised to bring a little retro style to your otherwise thoroughly modern project. Last month we featured a project that aimed to recreate the iconic mechanical VU meter with an Arduino and a common OLED display. ![]()
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