Vumeter attenuator ebuR68 and dbfs

[zamproject]

Hi Abbey

OK ! if we are talking mastering and hard limiting 0Vu @ -9dBfs work.
I usually monitor master or any music(mastered) with playback system gain/volume at -10dB, meaning in my analog chain 0PPM is absolute max program peak (minus 1 or 2 dB for the sub ms peak) and my Vu 8dB below show more or less the same in practice as the LU momentary.

Best
Zam

 

[zamproject]

For the OP
if your AD is +11dBu <=> 0dBfs (which is low...) you "should" set your 0Vu at -7dBu, like Abbey already say

But I'll be tempted to work IO at unity... since it's not the case with your interface with +16dBu DA and +11dBu AD maybe it deserve a try to pad 5dB at your output summing to also have +16dBu

Best
Zam

 

[JAY X]

OK, it is easy to become confused by this. First tell me what mixer you use for summing.

Cheers

Ian

Hi Ian!

It is my summing mixer design: New summing mixer

The gain structure:

Summing amps: G= Unity gain
Insert send : G = +6db DRV134
Insert return : G = 0db INA134
Fader amp : G = 9db
Balanced Trafo out : G = 6db
Total gain : 21db

I think i have to reduce the gain of some stages : The Insert return, to make it -6db and the fader amp to make it as a buffer with G = 1.

Also, now I realize how crappy is my audio interface. Today i searched for a new one, and found at least two at a reasonable price by Presonus and Ferrofish.
The presonus Studio and Quantum series at least have a gain of +18db in both the line inputs and outputs. It is a start..

Jay x

 

[zamproject]

Hi Jay

If you work at line level, you better lower the insert send to unity like input/sumamp, now usually fader amp have +10dB (for unity at -10dB fader position) but you already have 6dB with the trafo out (1:2 ?)

That's all personal, but I'll do unity until fader, then +4dB gain at the fader buffer.
This will give you IO unity with fader at -10dB position

Best
Zam

 

[abbey road d enfer]

The main problem here is that most of the USB powered interfaces are not designed to work at conventional +4dBu level, particularly the input side.
I have found it the hard way, using a NI Konnekt for measurements. According to specs, the max Line input level is supposed to be +20dBu. However, in practice there is a limiter that starts more than 20dB below that, so in order to have correct measurements I have to attenuate the signal externally.
So, going back to the original question, I think when using an analogue chain before A/D conversion, an attenuator is necessary for allowing the VU-meters to display the frequent elevated levels, and an attenuator for interfacing with inadequate inputs.

 

[ruffrecords]

Hi Ian!

It is my summing mixer design: New summing mixer

The gain structure:

Summing amps: G= Unity gain
Insert send : G = +6db DRV134
Insert return : G = 0db INA134
Fader amp : G = 9db
Balanced Trafo out : G = 6db
Total gain : 21db

I think i have to reduce the gain of some stages : The Insert return, to make it -6db and the fader amp to make it as a buffer with G = 1.

Jay x

One problem with stand alone summers is that you only have master gain control - so if all the inputs are about 0dBu, for example, with 16 inputs the output level from the mix amp will around +12dBu for typical programme material. This means your master gain control has to be at -12dB just to drop the output level back down to 0dBu.

Anyway, this is not our concern here - it is the levels out of and into the interface. Out of the interface is not much of a problem because typical summers (especially passive ones) can handle just about any level an interface throws at it. The real problem is taking the stereo sum back into the interface. All interfaces have a maximum signal they can take which usually relates to 0dBFS once converted. The actual level they can take varies enormously so the first thing you need to know is exactly what this level is. Once you know that you can set your VU sensitivity to correspond the desired dBFS. To make sure the interface is not overloaded, the VU meter needs to read tha actual fader snnt to the interface i.e. post the master gain control.

Cheers

Ian

 

[JAY X]

Hi!

With -7dbu relative to -18dbfs, the input level to the interface is hot as hell, and i have to switch on the line input pads. Makes difficult to calibrate the vumeters. Besides i think i have too much gain in the output fader. Most summing mixers out there, just have an attenuator. Or less gain, say 6db.

 

[Gold]

I use -16dBfs=0VU. I started using that because I started with a Lynx II many years ago and that's what they used. In mastering this doesn't work because of the loudness wars with make you want to work at more like -8dBfs = 0VU for final level. The -16dBfs reference level leaves plenty of headroom for me. I usually work at a lower level than that not hitting 0VU very often.

This is the main reason I have a passive monitor. I never have to worry about the monitor distorting with high levels.

 

[abbey road d enfer]

Hi!

With -7dbu relative to -18dbfs, the input level to the interface is hot as hell, and i have to switch on the line input pads.

That is normal. Your mixer is active, innit? So the output is Line level.