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VU scale for LED vu display

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Anonymous
August 26, 2004 4:18:09 PM

Archived from groups: rec.audio.pro (More info?)

I am building a high resolution VU LED meter which will have 60 LED's.
The scale will be in dB's. I want to know how to calculate or select a
suitable range, for example what dB will each LED indicate and what dB range
should the whole 60 LED's cover.

More about : scale led display

Anonymous
August 26, 2004 4:18:10 PM

Archived from groups: rec.audio.pro (More info?)

Marcus Tait <marcus_tait(NO_SPAM)@btinternet.com> wrote:
>I am building a high resolution VU LED meter which will have 60 LED's.
>The scale will be in dB's. I want to know how to calculate or select a
>suitable range, for example what dB will each LED indicate and what dB range
>should the whole 60 LED's cover.

Well, what are you measuring?

There are a bunch of different standards for bar graph meters out there,
including some BBC standards, some Scandinavian broadcasting standards,
and a couple ANSI standards. You can pick whichever you want. None of
them are VU meters, though.

A real VU meter has a particularly defined scale and particular ballistics.
Check out the RTW catalogue if you want to see some bar graph meters that
emulate VU needle movements.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 26, 2004 7:59:55 PM

Archived from groups: rec.audio.pro (More info?)

<< I want to know how to calculate or select a
suitable range, for example what dB will each LED indicate and what dB range
should the whole 60 LED's cover. >>

Make it variable. A high res mode for mastering showing just the top 15 or 20
db, a middle mode for tracking that displays maybe 40 to 50 db, & a test mode
that can show a noise floor in the 90s.


Scott Fraser
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Anonymous
August 26, 2004 10:08:57 PM

Archived from groups: rec.audio.pro (More info?)

In article <cgkke1$ph4$1@hercules.btinternet.com> NO_SPAM)@btinternet.com writes:

> I am building a high resolution VU LED meter which will have 60 LED's.
> The scale will be in dB's. I want to know how to calculate or select a
> suitable range, for example what dB will each LED indicate and what dB range
> should the whole 60 LED's cover.

If it's for a digital system (not a VU meter, technically) then I'd
have the LEDs be 1 dB per step, from -60 to 0 dBFS.

If it's for an analog system, how much headroom above 0 VU do you want
to display?



--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
August 27, 2004 4:16:21 AM

Archived from groups: rec.audio.pro (More info?)

Marcus Tait wrote:

> I am building a high resolution VU LED meter which will have 60 LED's.
> The scale will be in dB's. I want to know how to calculate or select a
> suitable range, for example what dB will each LED indicate and what dB range
> should the whole 60 LED's cover.

Do you actually mean a *VU* meter ?

The Bell spec VU meter covers -20dB to +3dB ref 1.228V.

It also has slow ballistics as a result of the moving coil movement in the
original spec. This makes the *VU* meter respond differently to various music
sources and limits its usability esp in digital recording. LED 'copies' tend to
mimic the ballistics by use of time constants in the rectifier circuitry.

Do you mean a *level* meter ? It's possible to make one today using LEDs that's
almost instantaneously responding. Fast response meters have in the past
typically been referred to as PPM types ( peak program meter ) since they
measure the peak signal level ( useful for avoiding clipping ) in a way that
*VU* meters don't.

If you're not interested in mimicing the original VU scale - then the choice is
entirely yours.

1dB per LED might be a good choice.

You might wish to choose the range +20dBu to -39dBu. Since much digital
equipment clips ( ie has its digital full scale ) at +19dBu then a LED at +20
would be a reliable 'overload' indicator.


Graham
Anonymous
August 27, 2004 5:16:41 AM

Archived from groups: rec.audio.pro (More info?)

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:412E6F45.447583D9@hotmail.com...
> It also has slow ballistics as a result of the moving coil movement in the
> original spec. This makes the *VU* meter respond differently to various
music
> sources and limits its usability esp in digital recording.

VU meters are traditionally used in conjunction with some sort of a peak
indicator. This combination is far more useful than the nearly useless
non-standard LED displays that have become common on digital gear.

--
Bob Olhsson Audio Mastery, Nashville TN
Mastering, Audio for Picture, Mix Evaluation and Quality Control
Over 40 years making people sound better than they ever imagined!
615.385.8051 http://www.hyperback.com
Anonymous
August 27, 2004 6:44:40 AM

Archived from groups: rec.audio.pro (More info?)

Bob Olhsson wrote:

> VU meters are traditionally used in conjunction with some sort of a peak
> indicator.

Rather rarely in my own experience. In fact the number of times I've seen that
combination I reckon I could count on the finger of one hand.

> This combination is far more useful than the nearly useless
> non-standard LED displays that have become common on digital gear.

Without reference markings they would certainly be useless.


Graham
Anonymous
August 27, 2004 12:53:17 PM

Archived from groups: rec.audio.pro (More info?)

Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
>Bob Olhsson wrote:
>
>> VU meters are traditionally used in conjunction with some sort of a peak
>> indicator.
>
>Rather rarely in my own experience. In fact the number of times I've seen that
>combination I reckon I could count on the finger of one hand.

It is used far too rarely in my opinion.

>> This combination is far more useful than the nearly useless
>> non-standard LED displays that have become common on digital gear.
>
>Without reference markings they would certainly be useless.

Even worse, most of them have too few segments to be really useful, and even
if they do, they usually have very weird scales so there is not enough
resolution in the top 12 dB or so.

That's basically what drove me to spend more money on an RTW meter than I
paid for the DAT machine I plugged it into. RTW does bar graph metering
right.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 27, 2004 4:16:19 PM

Archived from groups: rec.audio.pro (More info?)

In article <412E9208.C0CD274D@hotmail.com> rabbitsfriendsandrelations@hotmail.com writes:

> Bob Olhsson wrote:
>
> > VU meters are traditionally used in conjunction with some sort of a peak
> > indicator.
>
> Rather rarely in my own experience. In fact the number of times I've seen that
> combination I reckon I could count on the finger of one hand.

My TASCAM 5 (my first mixer that looked like a console) had peak LEDs
on its VU meters that went on 10 dB above 0 VU. So does the TEAC 6100
tape recorder that I have in my living room. So do the VU meters on
the stereo bus of my Soundcraft 600 console.

Admittedly, that's pretty ancient stuff, but I keep right up to date
by watching the VU meters on the console while glancing at the (peak)
meters on my DAT or A/D converter to give me an idea of how close to
full scale I'm getting.

But as Bob says, most modern LED ladder meters are pretty useless in
both the analog and digital environment.



--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
August 28, 2004 2:55:22 AM

Archived from groups: rec.audio.pro (More info?)

"Mike Rivers" <mrivers@d-and-d.com> wrote in message
news:znr1093603522k@trad...
> My TASCAM 5 (my first mixer that looked like a console) had peak LEDs
> on its VU meters that went on 10 dB above 0 VU. So does the TEAC 6100
> tape recorder that I have in my living room. So do the VU meters on
> the stereo bus of my Soundcraft 600 console.
>
> Admittedly, that's pretty ancient stuff,

VU meters started out in broadcasting during the 1940s where you always had
a peak indicator in addition. Disk mastering systems also had peak
indicators.

--
Bob Olhsson Audio Mastery, Nashville TN
Mastering, Audio for Picture, Mix Evaluation and Quality Control
Over 40 years making people sound better than they ever imagined!
615.385.8051 http://www.hyperback.com
at yahoo
Anonymous
August 28, 2004 8:15:43 AM

Archived from groups: rec.audio.pro (More info?)

Bob Olhsson wrote:

> "Mike Rivers" <mrivers@d-and-d.com> wrote in message
> news:znr1093603522k@trad...
> > My TASCAM 5 (my first mixer that looked like a console) had peak LEDs
> > on its VU meters that went on 10 dB above 0 VU. So does the TEAC 6100
> > tape recorder that I have in my living room. So do the VU meters on
> > the stereo bus of my Soundcraft 600 console.
> >
> > Admittedly, that's pretty ancient stuff,
>
> VU meters started out in broadcasting during the 1940s where you always had
> a peak indicator in addition. Disk mastering systems also had peak
> indicators.

Given the slow response of VUs, some method of warning of transmitter overdrive
was a good idea.

Whenever I see US radio studios on film / video where the console is shown, the
meters always seem to be pegging. That may possibly include documentary stuff
but I can't reacll for sure now.

Ok, there'll be a limiter somewhere down the chain but do US stations really
push the audio that hard ?


Graham.
Anonymous
August 28, 2004 11:48:08 AM

Archived from groups: rec.audio.pro (More info?)

Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
>
>Given the slow response of VUs, some method of warning of transmitter overdrive
>was a good idea.

The best arrangement I have seen was at WREK, where the operator on duty got
the VU meters on the air board, and a meter that showed how much the air chain
compressor was compressing. This let him set levels so the air chain compressor
was happy, and the compressor exists to set levels so the limiter is happy.

>Whenever I see US radio studios on film / video where the console is shown, the
>meters always seem to be pegging. That may possibly include documentary stuff
>but I can't reacll for sure now.

This might be in part because stations don't have real operating engineers
any more, and the announcers operate the board. And most of them do not
seem to have a good sense of this stuff.

>Ok, there'll be a limiter somewhere down the chain but do US stations really
>push the audio that hard ?

Plenty of major market stations have less than 10 dB difference between peak
and average levels. We got one in a local (small) city with less than 6.
They have a seperate processing chain for the announcer's voice, because if
the announcer was run through the chain they used for the music, it would
sound too distorted. I know this sounds like a joke but it's not.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
!