Vumeter attenuator ebuR68 and dbfs

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JAY X

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Hi!

As different producers would align their DAW mixers at different levels: (-20dbfs, -18dbfs, -16dbfs, -14dbfs), ¿would it make sense to have an attenuator in a needle vumeter? in order not to have to adjust the gain each time.

jay x
 

zamproject

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Hi Jay

If you have to align Vu for each session, then yes, an instant switch make sense
But this will not align line level reference accordingly in the analog chain (if there is some)
Were is the Vu in your chain ? just DAW output monitoring ?

Best
Zam
 

JAY X

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Hi Zam!

The VU is already post-fader in a summing mixer. And i want to make it also pre-fader, to help align daw gain, and not to rely on a vumeter plugin...

jay x
 

ruffrecords

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The problem is you first need to know the interface input level in dBu corresponding to 0dBFS. Unfortunately there is not standard for this and it practice it caries over a wide range.

Cheers

Ian
 

ruffrecords

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Well, if it is a professional set up you should measure the level the interface needs for 0dBFS. Use a calibrated signal generator of just build one of my pocket oscillators which you can easily calibrate to give 0dBu output at 1KHz (I will send you a PCB for free).. Just feed that into your interface and see what dBFS you get.

Just drop the sign of whatever reading you get and that is the dBU for 0dBFS. So, with 0dBU going in, if you measure -12dBFS then 0dBFS = +12dBu, if it reads -20dBFS then 0dBFS = +20dBu. Then you are in a position to tweak you VU meter for whatever your standard recording level is.

Hope hat helps.

Cheers

ian
 

zamproject

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Hello
So, in practice it is better to adjust the gain with a trimpot.
What is your practice ?
studio with same ADDA and various user requesting various references
or your summing unit will travel in various studio with various ADDA ?

In a more general way, if you don't care about summing internal level ref, you don't need to know the ADDA 0dBfs ref
Just send a -18fs (or watherver ref you want),mixer @ unity gain, and adjust meter to read 0Vu.

Best
Zam
 

ruffrecords

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I don't use a computer fro recording so some of this is guesswork. I assume the meters on most DAW software just hits the top stop at 0dBFS. So, how about someone making a VU meter plug in that can be set so 0VU us an dBFS you like.

Cheers

Ian
 

JAY X

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Hi!

I initially started this thread because i saw this vumeter: 2U Stereo VU Meter - Crookwood

and because i was not sure if my practice calibrating the vumeters in my summing mixer was correct. But i think i have finally understood. It does not matter if I have the vumeter post-fader. All I have to do is measure at the mix output jacks, or the VU buffer, with the multimeter, the level i need to send to the Vumeter for proper calibration: 0.616v, 0.775v, 1.23v etc... And this will be my reference level. Maybe i have to think to make the trimpots accessible from the front panel...:LOL:

Also this morning I think I have finally understood how to use the EBU R68 reference levels. It very depends on the specs of the audio interface. In my case a humble Behringer UMC1820. Its max output level is +16dbu.

So, if I choose the REF level to be :

-18dbfs/ 0dbu / 0.775v and the UMC1820 output level is +16dbu

Then the calibration point should be: -18dbfs + 16dbu = -2dbu / 0.616v.

Thus the headroom will be: -2dbu +2dbu (to match the 0dbu ref) + 16dbu umc1820 output = 18dbu of Headroom.

I thinks this is correct.
Jay x
 
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abbey road d enfer

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Hi!

I initially started this thread because i saw this vumeter: 2U Stereo VU Meter - Crookwood
The justification for the attenuator on this unit is that many people are operating at much higher levels today.
The most current semi-pro "standard" is +18 dBu at 0dBfs (100%)
Conservative mixes produce peaks between -3 and 0 dBfs, with a DR index of 12dB they produce an average level between 0 and +3dBu (-4/-1VU), which results in a readable needle.
However, many mixes are no more conservative, which results in the needle permanently pegged.
In the case of the pro "standard" of +24 dBu at 0dBfs (100%), the situation is worse by 6 dB.
Anyway I think mechanical meters are inapt at producing the type of information needed for digital recording, which suffers no overload above 100% fs.
I often see people using VU-meters having to rely on their ears for detecting overload, which is OK by me because the ear is the final judge, but just proves the inanity of using VU-meters.
 

ruffrecords

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Hi Jay, isn't your summing box going to be connected to the UMC1820 input not the output? So you need to know what level at the input relates to -18dFS.

Cheers

Ian
 

JAY X

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Hi Jay, isn't your summing box going to be connected to the UMC1820 input not the output? So you need to know what level at the input relates to -18dFS.

Cheers

Ian

Hi Ian!

Well, the Daw outputs go to the summing inputs, andthe output of the summing mixer goes to the interface inputs. I control the level that goes to the interface inputs with the output level potentiometer of the summing mixer. The interface max input level is +11dbu....I don't understand the second part referred to the input level and -18dbfs... here i'm lost...:whistle:
 

gswan

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I don't use a computer fro recording so some of this is guesswork. I assume the meters on most DAW software just hits the top stop at 0dBFS. So, how about someone making a VU meter plug in that can be set so 0VU us an dBFS you like.

Cheers

Ian
I've used the Klanghelm VU meter plugin on mastering playback which allows calibration at any FS level, I usually set 0VU=-9dBFS as this is about where a CD level might be.
On the outboard mechanical VU meters I do much the same, calibrating them according to the mastering level. The are useful in showing how hot the LF end is but apart from that they are just window dressing these days. There are better metering options available for digital work.
 

zamproject

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hi
0VU=-9dBFS
that's about 10dB too hot for Vu balistic :oops: are you sure it's not a PPM meter ?

my DAW is mostly a digital tape playback system, mixing analog ( and record back 2TK to the DAW), I have both Vu (simulated ballistic via plasma bargraph) and PPM galvanometer, my line level "unity gain" ( analog) is set at -10dBfs, as 0 PPM.
0 Vu is 8 db below (-18dBfs)
With a "proper" mix, 0VU and 0PPM match more or less, wile DAW true peak can show -4 or -3 dBfs (6dB fast transient overshoot)
if you want more density push the VU to overdrive, if you want more dynamic push the PPM to overdrive

I have some LU etc... meter in the DAW, where you can adjust ref and ballistic ad vitam (like a Vu or PPM)... the result is the same as analog except it can show inter-sample and transient shorter than the ms if you want (can help sometime), but so far analog needle can't be replaced by needle on a screen to visually feel the energy (when your earing after hours of mix can be compromised)

Best
Zam
 

gswan

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hi

that's about 10dB too hot for Vu balistic :oops: are you sure it's not a PPM meter ?
No, it's a VU meter and the VU ballistic is the same. The meter is being fed with the correct current for the VU reading, however the circuitry prior to the VU meter is performing the gain operation to allow calibration to an incoming signal.

 

zamproject

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however the circuitry prior to the VU meter is performing the gain operation to allow calibration to an incoming signal.
meaning ? it still show 0Vu with a -9dBfs 1k test tone ?
sorry but I have hard time to understand how you can have a 0Vu @ -9FS and not overshoot digital 0FS ?

Best
Zam
 

ruffrecords

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Hi Ian!

Well, the Daw outputs go to the summing inputs, andthe output of the summing mixer goes to the interface inputs. I control the level that goes to the interface inputs with the output level potentiometer of the summing mixer. The interface max input level is +11dbu....I don't understand the second part referred to the input level and -18dbfs... here i'm lost...:whistle:
OK, it is easy to become confused by this. First tell me what mixer you use for summing.

Cheers

Ian
 

abbey road d enfer

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I have hard time to understand how you can have a 0Vu @ -9FS and not overshoot digital 0FS ?
It all depends on the actual DR index. At calibration, a sinewave at 0 VU corresponds to +3dB peak. That means that the peak voltage achievable without digital overload is 12 dB above, which is compatible with many mixes.
And highly compressed mixes will allow increasing the average level by a few dB.
That is certainly not what I would recommend for tracking, but can be considered acceptable in view of certain practices for mixing
gswan's comment "I usually set 0VU=-9dBFS as this is about where a CD level might be" just shows that most of the CD's he uses as reference are in this ballpark, with a DR index od about 9dB, which means they are slightly overcompressed compared to the average (which is a moving target, since the Loudness War keeps on increasing this average). The average DR index varies very much with the type of music, classical and jazz being at one end of the spectrum and death metal at the other*).
I believe this page resumes quite well the situation, although they don't use the simple metrics of peak and rms value, which is the essence of this thread.

*In broad terms, though. This page
shows that pop, country and latin are not immune.
 
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