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VU Meters: Let's See 'Em!!

RayDunzl

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#2
What I watch is something I made 20 years ago...



WTF is that?

It's a fuzzy picture of , uh, well, ok...

It connects across the amplifier outputs.

The upper LED's are red.

The outer LEDs (top, left and right) start to turn on at about 1V of speaker drive.
The inner LEDs (top, left and right) start to turn on at (maybe) 4V of speaker drive (I forget).
The topmost LEDs illuminate with a positive going signal, the ones below with a negative going signal.

The bottom row are tri-color LEDs, red/green/yellow, and turn on with the same voltages. Outer ones turn on first, at lower voltage, inner turn on at higher amplifier output.

You can see how the outer ones are brighter than the inner above. 2-stage display.

If the signal is balanced in the positive and negative directions, they glow yellow (alternate red and green mixed by the eye).

If the signal is offset toward the positive direction, they glow more green, negative direction, more red. Brass instruments often have such an unbalanced waveform.

So, it's a nice little dancing lights display that is real-time with no latching - every wave that is strong enough to turn them on turns them on with the brightness relative to the instantaneous voltage level.

When playing softly, just the outer ones barely turn on. Loudly, it can be rather bright, but I never find it annoyingly so.

LEDs don't lag, so a wave would turn on the upper LED then go dark (zero crossing) then light up the lower LED. The eye does lag, so unless the wave is below 20Hz or so, you don't see them flashing, just glowing along with the intensity of the amplification.

Easy build, 4 resistors and 12 LEDs and some wire and solder and a little project board.

---

But you asked about VU meters...

I have a VU meter (screen display) on a Behringer DEQ2496 in the chain, but I don't use it, preferring to watch a real-time spectrum of what's in the air.
 
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dallasjustice

dallasjustice

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Thread Starter #3
That one would make more sense with a video. I bet it's kewl.
 

Sal1950

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#4
My components approx 1985?
PhaseLinear1_v1.jpeg

PhaseLinear1.jpg
 

TBone

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#6
:oops: no recording into the red anymore ... miss the days when saturation looked cool ...

.. w/digital recorders I've used, only 1 (pro Sony unit) offered accurate, quick, peak meters indicating proper clipping.
 

NorthSky

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#8
I got some nice vu from here. Some blue, some white, some orange, some green. Marantz, Kenwood, Yamaha, Pioneer, Mountain views.
My camera was stolen, my pictures too, and my cell camera was out of order when I dropped it on the cement floor from upstairs.

What I could do though is google my units and get those vus. ...Some of my units were stolen too.
 

fas42

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#9
And I've got a nice vu through the lounge room glass - over trees and hills and all that sort of good stuff ...
 
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dallasjustice

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Thread Starter #12
Since db is only a relative measurement, I am not sure what 0db refers to on an amp VU meter. Is fair to assume it represents maximum continuous power?

Can one tell the output in watts from an amp VU meter? Would 0db be the equivalent to the max continuous watts spec? If so, then maybe a decibel to power ratio could be used to estimate the power the amp is using? For example, if the max continuous is 120w into 8ohms and the meter shows -20db (.01 power ratio), then the amp is using 1.2 watts at 8ohms? Does this make any sense or am I just making this shit up?
 
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Sal1950

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#13

Sal1950

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Since db is only a relative measurement, I am not sure what 0db refers to on an amp VU meter. Is fair to assume it represents maximum continuous power?

Can one tell the output in watts from an amp VU meter? Would 0db be the equivalent to the max continuous watts spec? If so, then maybe a decibel to power ratio could be used to estimate the power the amp is using? For example, if the max continuous is 120w into 8ohms and the meter shows -20db (.01 power ratio), then the amp is using 1.2 watts at 8ohms? Does this make any sense or am I just making this shit up?
Come bro, don't go all tech on us. They're just there to make the amp look sexy. And they do. LOL
 

RayDunzl

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#15
Since db is only a relative measurement, I am not sure what 0db refers to on an amp VU meter.
Wiki:

The original VU meter is a passive electromechanical device, namely a 200 µA DC d'Arsonval movement ammeter fed from a full wave copper-oxide rectifier mounted within the meter case. The mass of the needle causes a relatively slow response, which in effect integrates the signal, with a rise time of 300 ms. 0 VU is equal to +4 [dBu], or 1.228 voltsRMS across a 600 ohm load, or about 2.5 milliWatts. 0 VU is often referred to as "0 dB".

Can one tell the output in watts from an amp VU meter?
Wiki:

"The VU-meter (intentionally) "slows" measurement, averaging out peaks and troughs of short duration, and reflects more the perceived loudness of the material "

Does this make any sense or am I just making this shit up?
Nice try, but that really isn't the purpose of the VU meter on musical material, unless you just want some average power reading. Even so, the meters may be inaccurate at low levels.

Wiki:

"Typically the levels to be considered when designing systems using a VU meter are:
  • Reference Level (typically +4dBu, valid with tones only)
  • Standard Output Level (10dB above Reference, typical peak levels)
  • Clip Level (6dB above Standard Output Level, "headroom" to allow for unusual conditions)"
That says, to me, that with music, a reading of 0dB on the VU meter could (sometimes) include a signal that (momentarily) is up to 16dB higher.
 
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NorthSky

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#16
Michael, 0dB is your amp power rating. If you look @ my VU meters on my Kenwood receiver, 0dB is 50 Watts (8 Ohms rating) for my receiver model.

On your Luxman M-700u stereo amplifier's 0dB represents the rating of its amp into your speaker's load, and in stereo or mono mode → http://www.luxman.com/product.php?pid=52

"Stereo output is rated at 120W per channel into eight ohms and 210W per channel into four ohms, achieving up to 840W per channel into one ohm instantaneously. There is also a user-selectable mono mode with a rated output of 420W into eight ohms."
 
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Thomas savage

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#17
I loved the VU meters on my dads old hifi when I was a child. They fascinated me, they fluidity of movement for one coupled with the 'naughty' aspect of going into the red.

Can't say I am that fussed these days though.

image.jpeg

The pre amp looked like this though, VU meters must of been on the amp... Or just in my mind :D
image.jpeg
 
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Sal1950

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#18
I loved the VU meters on my dads old hifi when I was a child. They fascinated me, they fluidity of movement for one coupled with the 'naughty' aspect of going into the red.

Can't say I am that fussed these days though.
Your dad? Your dad's HiFi had a crank and a horn. :p
 

RayDunzl

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#19
Does this make any sense or am I just making this shit up?
If you are referring to your amplifier, as in the first post, to which I did not refer, it doesn't have VU meters. Power meters, yes, VU, no. And from there, probably "yes" to the power ratio query, depending on the accuracy of the calibration.

Looking at the the spec sheet - I'd feel safe assuming 0dB = 120/240/480w into 8/4/2 Ohms, with 6dB headroom available, and with the power ratios you mentioned for lower levels.

If you look @ my VU meters on my Kenwood receiver, 0dB is 50 Watts
I doubt those are VU meters.

Quit confusing me!
 
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