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-18 or -16 digital ref level?
Old 20th March 2003
  #1
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paterno's Avatar
 

-18 or -16 digital ref level?

Just wondering if anyone out there has been running their digital gear at a ref level of -16? I had been thinking of re-calibrating my PTools rig, and i did it this afternoon. I did it at -16 so the level coming out would be a little more manageable on an analog console (faders more toward unity gain than in the bottom third of the throw), and also so i wouldn't have to crank the output gain of some of my analog gear on my way in to get a decent level into the computer.

Any thoughts?

John
Old 20th March 2003
  #2
I think I am at -18

Jules
Old 20th March 2003
  #3
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doug_hti's Avatar
 

-16.... I may go to -14 though...If I worked with post, I would stay around -18 to compensate, but since I don't, I see nothing wrong with -16 or even -14
Old 20th March 2003
  #4
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heylow's Avatar
 

Kind of on topic.....kind of off, I guess.

I dont use PT so my question may seem odd in spots...
bear with meheh

When you guys set your reference point, say to -15 , are you guys generally peaking or RMS'ing there?

Also, for you guys going out to analog boards, which "plays" nicer with the analog board and outboard comps and such....the peaking or RMS'ing?


Thanks...

heylow
Old 20th March 2003
  #5
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We have an analog desk, we've been at -16 for several years.
Old 20th March 2003
  #6
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Re: Re: -18 or -16 digital ref level?

Quote:
Originally posted by Kent

So, anyhow, in short... -16dBfs is a hotter reference level than -18dBfs. This would then mean that you would have to crank your outboard up even more in order to acheive this reference level on the inputs of your A/D and then there is the potential for your D/A levels to cause your analog console's faders to be even closer to the bottom of their travel while mixing. Perhaps the additional 2dBfs in level could even cause your console's input stage to clip more often.
Not quite. When you change your reference level from -18 to -16, you are taking down the output level of the system. To keep the whole thing at unity gain through the system, you need to boost the input gain to compensate. I'm not sure you are understanding my original post.

BTW, what do you mean by the dBfs notation?

-John
Old 20th March 2003
  #7
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e-cue's Avatar
 

-16 here... I have an 888 that I cal "wild" because I mainly use it as sends to a Forat and other nicknacks.
Old 20th March 2003
  #8
It really depends on the source. I adjust the A/D conversion on a track by track basis. It can be anywhere from -18 to -12.
Old 20th March 2003
  #9
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I don't know how to do this calibration stuff.

What I've done is send a 1kHz sine wave generated in my daw through D/A at -.1db. I then fed the signal back into A/D and adjusted the inputs so that they were just below clipping. I verified in my daw that the incoming signal was -.1db.

Am I doing something wrong? Why do you all adjust unity at A/D to be -17? Is this so you don't have to apply as much gain in the analog stage?

I realize my question is a "newbie" question and I hope someone has the patience to answer it.

Thanks,
FF
Old 20th March 2003
  #10
I wouldn't worry about it Fae...I had mine permanently cal'ed to -16, and sometimes it was too much, sometimes not enough. So right now I just do it by eye. I set the analog gear as close to unity as possible. Crank the A/D as close to full scale as possible without clip (on the preamp or the A/D, which can be quite different BTW). It may be a seat of the pants way to do it, but it works the way I need it to. I don't view it any differently than turning the output knob of a compressor up or down.


Quote:
Originally posted by paterno
Not quite. When you change your reference level from -18 to -16, you are taking down the output level of the system. To keep the whole thing at unity gain through the system, you need to boost the input gain to compensate. I'm not sure you are understanding my original post.
I think he understands your original post just fine John, and he is right. -16 is a hotter level than -18. If you take it from -18 to -16 you are making the output level of the A/D louder, not "taking it down". Unless both Kent and I are totally off base, and the people who have taught me this **** are completely off too. If you aren't getting hot enough levels to 24 bit digital and your analog gear is within normal levels, just turn up the convertor. Again, it's all dependent on the source. A gorilla on the drums, isn't going to need the same level as a nervous folk singer.
Old 20th March 2003
  #11
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Quote:
Originally posted by NathanEldred
quote:
--------------------------------------------------------------------------------
Originally posted by paterno
Not quite. When you change your reference level from -18 to -16, you are taking down the output level of the system. To keep the whole thing at unity gain through the system, you need to boost the input gain to compensate. I'm not sure you are understanding my original post.
--------------------------------------------------------------------------------
I think he understands your original post just fine John, and he is right. -16 is a hotter level than -18. If you take it from -18 to -16 you are making the output level of the A/D louder, not "taking it down". Unless both Kent and I are totally off base, and the people who have taught me this **** are completely off too. If you aren't getting hot enough levels to 24 bit digital and your analog gear is within normal levels, just turn up the convertor. Again, it's all dependent on the source. A gorilla on the drums, isn't going to need the same level as a nervous folk singer.
Ah, I believe you are totally off base here. If you raise the input [the A to D] to -16, then you have to lower the output of the [D to A] to preserve unity gain throughout the SYSTEM, which was what my original post was about. Unity gain with a different ref level. As an example here, unity gain on my LA-3a is at number 6 with no gain reduction. To get an acceptable 'digital level' into ProTools, I have to increase that gain by at least number or two. [for those with LA-3a experience, I have done the 'low noise' mod --some units the unity gain point is around 4]. So now I am having to boost my LA-3a and make it's gain stage work harder to get a decent level into the computer.

Nathan, I don't have an input gain knob on my converter, nor do i want one. And I never mentioned anything about not getting hot enough levels; I mentioned that with a -18 reference I have to increase the gain into Protools relative to something else analog, like a 2" tape machine, to get the maximum amount of level in to PTools. By re-referencing to -16, I have in effect turned up my input gain and turned down my output gain to better approximate how my analog gear works in it's originally designed context on the input side (basically getting a hotter level into the computer without having to add a lot of extra gain to the signal path), and to not hit the analog console as hard (and eat up headroom) on the output side.

Kent, thanks for the dBfs definition!

Cheers,
John
Old 20th March 2003
  #12
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how hot do you want to be in the computer?
and why so hot?

I've been fine sitting around -14 to -18 depending on the material.
and never even coming close to fs.
when you dump from 2" do you boost the **** outta the levels?
I run a straight up patch from the 2" into the RADAR feeding PT.
the level 'LOOKS' quite low but whilst keeping my gain structure like this it all makes sense at the end of the day.
Old 20th March 2003
  #13
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Steve Smith's Avatar
 

Good point Mike. I am at -18 on my PT rig.

The other great point Mr Tholen often makes is that we should all spens a little more time observing Odbu on out analog gear.... I hardly even look at the levels in PT anymmore ( within reason) and things are sounding way better around here then they do when i a slamming my analog gear to get the level up. YMMV.
Old 21st March 2003
  #14
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paterno's Avatar
 

Quote:
Originally posted by Mike Tholen
how hot do you want to be in the computer?
and why so hot?

I've been fine sitting around -14 to -18 depending on the material.
and never even coming close to fs.
when you dump from 2" do you boost the **** outta the levels?
I run a straight up patch from the 2" into the RADAR feeding PT.
the level 'LOOKS' quite low but whilst keeping my gain structure like this it all makes sense at the end of the day.
why hot? to take advantage of the bit depth, the same way you try to maxmize the level to 2" for better signal to noise. It may not be as drastic a difference, but when you're mixing stuff cut on PRoTools [with maxed out levels at the -18 ref] through an analog console, you do [or at least I do] have to worry about clipping the inputs/line amps of the console. This will affect the way the whole channel reacts, especially the gain available in the EQ before clipping.

And, again, I'm talking about a REFERENCE LEVEL FOR THE SYSTEM. 0dB in = 0dB out. Why not keep the exact same scenario you posed about keeping your gain structure intact, while at the same time getting your best/hottest level into Protools, and to some small degree a better signal to noise ratio? That is all I'm talking about. We do that with tape machine alignments all the time, don't we? Same basic principle, although the tape machine has a much more noticeable sonic difference. That's why we align at different ref levels...

No, I don't 'boost the **** outta the levels' when transferring from 2". It is a direct, hard patch out of the 2" into Ptools. In a properly calibrated system, at a -18 ref [ that is, INPUT and OUTPUT calibrated to the ref level] the meters in Ptools will look lower than a -16 ref, but the output as far as the transfer goes will still look 0VU at the console. At -16 ref, you will have a hotter level into the system, but because you are calibrated at -16 you have turned down the output to compensate and keep the overall I/O at unity. There is just a higher level recorded into the system...

-John
Old 21st March 2003
  #15
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Quote:
Originally posted by Steve Smith
Good point Mike. I am at -18 on my PT rig.

The other great point Mr Tholen often makes is that we should all spens a little more time observing Odbu on out analog gear.... I hardly even look at the levels in PT anymmore ( within reason) and things are sounding way better around here then they do when i a slamming my analog gear to get the level up. YMMV.
If you are at -18 on your PT rig, do you just use your analog metering, and ignore the pTools metering? What are you doing about kicks,snares, and other percussion instruments? The VU is not fast enough to react to the transients of those kinds of sounds. You could very easily distort the signal while the VU meter looks fine.

My whole point of this ref level idea was because of analog 0VU vs. level into Protools!!!!!!!That was my original reasoning to change the ref level in the first place: To keep the reference closer to 'analog 0VU' while at the same time maximizing the signal level into Protools !!!!!!!!!!

PS -- Protools ships at -18. I'm not talking about simply changing the setting in the Preferences. If you change the ref in the preferences you have to recal the analog I/O (you know, all those trim pots) to truly insure you have a unity gain system. Otherwise the metering will not be accurate...

-John
Old 21st March 2003
  #16
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alphajerk's Avatar
 

Quote:
Originally posted by paterno
why hot? to take advantage of the bit depth, the same way you try to maxmize the level to 2" for better signal to noise.
that is a wrong way of thinking... UNLESS the window of the source material calls for it. the level to noise floor is way beyond the noise floor of my room, or a lot of rooms i have recorded in. best way to figure this out is to measure your room noise floor, and equipments noise floor, then your maximum source level... the difference is the window you ned your conversion to run.
Old 21st March 2003
  #17
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your being a little 'tweakey' here JP.
you really don't need to 'use up all the bits' on a per track basis...I at least haven't found any need to tweak my system to use up 'all the bits' while still maintaining unity gain throughout input to output.
there is NO noise/hiss in PT...what are you fighting with your 'all the bits' theory?
as for meters, I use a Siemens light meter most of the time.
nothing's faster. and old as ****.
otherwise I just eyeball it just like the old days.
peace-Mike
Old 21st March 2003
  #18
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Quote:
Originally posted by alphajerk
that is a wrong way of thinking... UNLESS the window of the source material calls for it. the level to noise floor is way beyond the noise floor of my room, or a lot of rooms i have recorded in. best way to figure this out is to measure your room noise floor, and equipments noise floor, then your maximum source level... the difference is the window you ned your conversion to run.
So, what you are saying is that maximizing of the input into your digital system is not a big issue? The analogy to 2" in the signal to noise area may not have been the best, but it was the first thing I thought of that is a completely 'tweakable' unity gain piece of gear. Besides that, how do you deal with levels, Alpha? Are you going for the highest level into the system?


Cheers,
John
Old 21st March 2003
  #19
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Quote:
Originally posted by Mike Tholen
your being a little 'tweakey' here JP.
you really don't need to 'use up all the bits' on a per track basis...I at least haven't found any need to tweak my system to use up 'all the bits' while still maintaining unity gain throughout input to output.
there is NO noise/hiss in PT...what are you fighting with your 'all the bits' theory?
as for meters, I use a Siemens light meter most of the time.
nothing's faster. and old as ****.
otherwise I just eyeball it just like the old days.
peace-Mike
Hey Mike --

yeah, I've had a week off and look what happens!!!!!! Getting all SuzyHomeMaker and everything. The fact is, this is really the only time I think about this ****. When I'm making a record, I'm thinking about making a record, [not the hard core technical stuff], and pretty much anything goes..

I guess it has to do with two things here that I have been running into more and more as my clients abandon 2" for whatever reasons: doing overdubs on existing PTools sessions where I have to keep the levels similar to what already exists (hence cranking the analog gear on the input side -- sometimes it just doesn't sound as good to me), and mixing stuff where the faders end up low, and boosting a lot of one frequency craps out the EQ, and things like that. You know, some EQ's have to be TURNED to get something out of 'em! I know you could mess with the line trims, or turn down the levels in PTools, but that would involve thinking in the fore-mentioned making the record stage, which for me always brings creativity to a halt. Know what I mean?...

Cheers,
john
Old 21st March 2003
  #20
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Quote:
Originally posted by paterno
If you are at -18 on your PT rig, do you just use your analog metering, and ignore the pTools metering? What are you doing about kicks,snares, and other percussion instruments? -John
I was making a blanket statement.. I do Look at the PT meters, I just dont freak anymore if something is - 16 or whatever, as long as it sounds good.

The point about maximising all those bits has been gone over a bunch on several boards. If you are using less than full scale, things do not sound worse with current converters, you just have less dynamic range ( again I am simplifing here) ... We do not need to be smashing level all the time in PT or whater dig medimum, although I do go hot if the gear I am using on the front and back end of whatever digital device will like it..
Old 21st March 2003
  #21
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yeah, why are people cranking the hell outta their analog gear to get into PT as hot as possible?
very frustrating to deal with in a professional enviroment.
having to compensate for poor gain structure with faders-trim pots-or whatever you have is a major sonicface**** ...kids these days have no idea what proper gain structure is all about.
It is possibly THE MOST IMPORTANT PART YOUR JOB! and if it ain't right somewhere some how it's gonna show.
I'm sorry , have i flipped yet?...
I'm just back from a crazy assed stint in Hollywood and I have no patience.
Old 21st March 2003
  #22
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Quote:
Originally posted by paterno
So, what you are saying is that maximizing of the input into your digital system is not a big issue? The analogy to 2" in the signal to noise area may not have been the best, but it was the first thing I thought of that is a completely 'tweakable' unity gain piece of gear. Besides that, how do you deal with levels, Alpha? Are you going for the highest level into the system?
i USED to until i talked with nika about it on the phone for a while... the deal is, you gain no resolution or anything by getting the level as hot as possible. what you have to worry about is your noise floor... your NATURAL noise floor... and your dynamic range.

take distorted guitar... probably the LEAST dynamic range of anything i deal with. high ADC level doesnt mean ****. its better to gain stage your gear going in so it sounds best and not worry about the level into the convertor. most 24 bit convertors have at least 107db dynamic range. thats a ****load more than a distorted guitar.

where you have to worry is with things that are VERY dynamic... but you also have to factor in the room noise floor at that point.... say you have something that has 80db of dynamic range. you then have to hit -27dbfs on its peaks, but probably more like -20dbfs for some safety room. drums are probably the biggest offenders that i deal with... cymbals more than other elements, like a cymbal fade will head into the room noise floor but striking a cymbal will produce some pretty good volume.


as for 2" you have less dynamic range and pleasurable compression when you sometimes hit it harder, digital doesnt do that. i would think that if your faders are too low on the analog board, you could probably get away with lower recorded levels. again, it depends on the source material.

most stuff i record peaks @ -10dbfs on my 1296. that gives me 10db to play with on the take... like a sudden scream from a vox might peak it @ -3dbfs. im still working out on my drums where i have them peak... it depends on the drummer most times. the kick/snare/toms i leave lower now and the overheads [sides, or rooms] i run hotter to err on the low side of the spectrum for cymbal fades and such.


so what you need to think about when recording digital tracks isnt the hottest level but accidentally losing the LSB with track material... that will probably get you higher in the sweet spots of the board [i dont like having my faders too low on analog boards.. but not cranked either] and give you headroom heading into the EQ section.
Old 21st March 2003
  #23
I'm with Mike Tholen and AlphaJerk. With 24 bits I don't think you have to worry about it being to full scale, that is a bit "tweaky" as Mike said. I want to have a good strong signal, but I still want headroom even after peak levels. If someone is using a good front end (mics, pres, adc) and really great players with good arrangements are in front of the mics, I'd be happy with 16 bit if it was a choice between that or full scale 24 bit and **** out in front.

Old 21st March 2003
  #24
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Its worth remembering too that if you need to mix anything internally....like a bunch of stems for example, hot levels will result in mush. The bit resolution arguement is one of the biggest misnomers in digital recording. You get no end of problems by slamming everything in. As if software summing isn't without its problems anyway! Best avoided if you can.
J
Old 21st March 2003
  #25
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I won't work with gear that doesn't have the requisite headroom... I run at -12dbfs... then again I also run a 'class A/discrete' desk that runs +26 at the output...
Old 21st March 2003
  #26
Gear Nut
 

-16db

Very interesting conversation. In my opinion it depends on the dynamic range of your program material.
I do alot of orchestral recording, where I'm faced with a huge dynamic range. My number one enemy is digital overload. When I see sustained reds on my PT meters I know I have something I can't fix. So I compromise. I've found, for me, -18 has given me the most freedom from worry. Now I'm cheating. I have forty channels of the cleanest preamps out there, so an extra db or two isn't gonna matter.
It all comes down to what you're doing.
Good Luck
Old 22nd March 2003
  #27
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Thanks to everyone for your replies and insights. Don't worry Kent, everything is documented!

I'm going to run at my new cal level for now to 'see how it feels'. Besides, it only takes about an hour to get it all back to the way it was...

Cheers to all...

-John
Old 22nd March 2003
  #28
jon
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Hi John,

One extremely common misconception out there is that bit depth has something to do with the quality of frequency response.

Bit depth deals with dynamics only.

At 16 bits, it made some sense to record hot to preserve some dynamic resolution with natural/acoustic sources.

At 24 bits, the 256x increase in resolution is such that tracking hot to optimize it is not an issue worth bothering about compared to the one of rational gain staging on the analog side.

Best -
Old 22nd March 2003
  #29
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alphajerk's Avatar
 

Quote:
Originally posted by jon
At 16 bits, it made some sense to record hot to preserve some dynamic resolution with natural/acoustic sources.
dynamic RANGE. not resolution. the resolution is the same.
Old 23rd March 2003
  #30
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The biggest consideration should be the headroom of your converters and the analog gear they interface. For example 888s actually sound lots better when you turn the trim pots down all the way. Likewise many console inputs and outputs sound better when they are run at lower levels. For example they run everything at Skywalker at zero rather than +4 simply because it sounds better, often LOTS better.
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