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[Mark D.]

Ideal A/D & preamp input levels can vary. But I've heard some going close to 0db at the A/D, or even preamp. At 0db input the preamp, with no further boost, peaks at -18db at the A/D. Lower preamp gain will reduce S/N of that & the A/D. Many pres have a 90db S/N, converters 110db. So unless it distorts, I can't imagine negatives in being near 0db at the pre. The question is if harm is done above -18db at the A/D. Driving a preamp input to distort...bad idea. But an output level control can bring what it sends to the A/D to, say, under -6db. Closer to the 110db S/N of the A/D. Well below clipping or intersample peaks, but with better S/N, which should be beneficial. I just want to hear thoughts that and experiences with that. (Edited & revised to clarify what I'd said.)

[jetbase]

Shouldn't everything be calibrated to be running at optimum? Forgive me if I get this a bit wrong (being a bit weak on some of the technical points), but 0dBFS is MAXIMUM level, and analogue levels are usually calibrated so that 0VU = +4dBu = -18dBFS. So if you want to run your preamp at an optimum level then you should be reading around -18 on your DAW meters. Practically, in my studio, I aim to peak between -15 to -12 in the DAW. This puts the levels in the right spot on the console meters, as well as ensuring preamps & AD converters have healthy levels on the way in.

[Geoff Emerick de Fake]

The +4dBu "sweet spot" is not justified any more.
Many designers are aware of the fact that more and more operators are operating at higher analog levels.
When everything was +4dBm into 600R, the equipment was optimised for that. It was important to make sure that the output stage would provide enough current to drive the load, but there was really no point in concentrating on operation at +18dBm, knowing that tape would crush it.
Today, the designers don't have to worry that much about driving a 10k load, but they have to make sure that signal integrity is preserved up to +20dBu operation. They have to take care of issues that didn't exist with tape, such as making sure their stuff does not produce overtones or spurious that some converters may not handle well (and that tape would have probably purely and simply ignored).

Optimizing the whole recording chain is not as simple as it used to be. You just made sure everything was calibrated at +4 and here you go. Today you may want to use a 60's preamp  for vocals, a modern mic channel for guitar and a Pod-like thingy for bass. The optimum level would probably be different; optimizing would require recalibrating the A/D converters.

Going back to the OT, I believe there must be enough people who mix on actual mixers, just by the fact that a company like Audient manages to sell about a dozen of their large mixers per month. I don't know the figures for the other companies in that segment (API, Midas, A & H, Neve, SSL), but I think there is a market that needs catering for. OTOH, all these manufacturers are clearly concentrating on mixer/DAW controller that they hope will be their future market.

Personally, I do mix on a mixer, a Tascam DM4800 (although some would actually deny the right to call it a mixer), that I use as a converter-router-mix bus-with EQ and FX. All the level changes I do ITB, so I don't need an automation; the channel faders could be rotary, that wouldn't change a thing for me.

[Mark D.]

Off topic, but after searching I didn't know where to ask. Dan Lavry has a white paper about disadvantages of going to 196 khz vs. stopping at 88.2 or 96 khz. Though his products reportedly now go that high, probably by consumer demand regardless of the very valid points he made. I wonder if he ever posted his thoughts on the over 1 mhz stuff used and strongly advocated for by Tom Jung. I am thinking that would be a heck of a debate. Not to side track. If such a thread exists, please let me know. Thanks.

[jetbase]

Mark D. wrote on Thu, 13 May 2010 07:49

Ideal A/D & preamp input levels can vary. But I've heard some going close to 0db at the A/D, or even preamp. At 0db input the preamp, with no further boost, peaks at -18db at the A/D. Lower preamp gain will reduce S/N of that & the A/D. Many pres have a 90db S/N, converters 110db. So unless it distorts, I can't imagine negatives in being near 0db at the pre. The question is if harm is done above -18db at the A/D. Driving a preamp input to distort...bad idea. But an output level control can bring what it sends to the A/D to, say, under -6db. Closer to the 110db S/N of the A/D. Well below clipping or intersample peaks, but with better S/N, which should be beneficial. I just want to hear thoughts that and experiences with that. (Edited & revised to clarify what I'd said.)

Mark, I'm sorry but I'm actually a little hazier on what you're asking, or suggesting, in your revised post. Are you simply saying that everything should be calibrated (in which case I would agree). I don't think that I've used a standalone preamp with an output control, unless it has a fine trim adjustment or a built in compressor with make up gain, but my main set of AD converters have adjustable input levels. Providing everything is calibrated correctly (& any faders at '0') then I should only have to worry about what the last meter in the chain says, unless of course I wanted to deliberately push the level on any piece in the chain (other than the AD) or sum more than one preamp/channel. In theory I should be able to simply set my preamp level by looking at the VU meter of the return channel on my console, aiming for '0'. In practice I find the meters on my particular console to be a little low in resolution & I end up looking at the digital meters on either my HDR (which is my DA from Pro Tools, +4dBu = -15dBFS on outputs) or DAW and aiming for around -15.

[Mark D.]

It can be a complex thing to describe in discussion. To try and simplify it. I'm a minimalist in recording. Pre to A/D to PC. I set my pre level so it never hits red, peaks in yellow. That's optimal. If my output on it is set to zero, I get that -18db in the DAW. I have recorded like that fine. If going hotter, raising the output so peaks hitting the A/D  are -6db instead of -18db (going by what I see in my meters, recording at 24 bit, in my DAW). When I had compared -18db peak recordings vs. -6db peak recordings, I'd heard nothing worse in the -6db recording. If anything, both normalized, I noticed more noise in the -18db. I wonder if others have. If there is no difference, someone will be getting 12 db better S/N ratio performance at their A/D, given that extra level. If the S/N ratio of that A/D, hypothetically, is 110db, that can make a noticeable difference on very quiet dynamic parts, especially after they're compressed. That since compression could make the noise floor more apparent. This is something others might want to test.

[jetbase]

I think I understand what you're saying. But if I recorded everything peaking at -6dBFS, even if I had no distortion in the recording, I would most likely get distortion when mixing. When I get sessions in to mix & everything is recorded hot I gain individual tracks down so that the line ins on my console are not being overloaded. I'm not sure if there are negative consequences if mixing ITB with tracks peaking at -6dBFS. But anyway, if the mic preamp sounds better at a higher gain setting then isn't the solution to calibrate the input of the AD converter to suit?

[Geoff Emerick de Fake]

jetbase wrote on Sun, 16 May 2010 19:16

But if I recorded everything peaking at -6dBFS, even if I had no distortion in the recording, I would most likely get distortion when mixing.

You would or would not. It all depends on the equipment. As I mentioned earlier, older mixers were optimised for 0 VU operation, newer ones are optimised for much higher operating level. Earlier converters also may not be happy to operate at +18dBu.

Quote:

When I get sessions in to mix & everything is recorded hot I gain individual tracks down so that the line ins on my console are not being overloaded.

What mixer? What gain structure? By "gain individual tracks down", do you mean reducing the gain in the DAW?

Quote:

I'm not sure if there are negative consequences if mixing ITB with tracks peaking at -6dBFS.

DAW designers expect users to do so, so they have all sorts of trickery   built-in in order to cope with that.

Quote:

But anyway, if the mic preamp sounds better at a higher gain setting then isn't the solution to calibrate the input of the AD converter to suit?

In terms of noise performance, definitely yes. In terms of distortion, that may well be possible. In a fixed-topology preamp, distortion increases almost linearly with gain; that would advocate for the lowest possible gain.
In fact it is important to make a distinction between gain and output level, although they are related. Again, in a fixed-topology preamp, increasing gain generally increases distortion (by reduction of gain-margin), and the related increase of output level (for a given input level) increases the distortion created in the output stage (except for crossover distortion).
But it is also very possible that a certain balance of input/output distortion be particularly euphonic. This should be your particular operating level for the preamp, to which you should match the A/D converter's operating level. The presence of transformers in the signal path may also steer to a different conclusion.

[jetbase]

Geoff Emerick de Fake wrote on Tue, 18 May 2010 03:05

jetbase wrote on Sun, 16 May 2010 19:16  But if I recorded everything peaking at -6dBFS, even if I had no distortion in the recording, I would most likely get distortion when mixing. You would or would not. It all depends on the equipment. As I mentioned earlier, older mixers were optimised for 0 VU operation, newer ones are optimised for much higher operating level. Earlier converters also may not be happy to operate at +18dBu. Quote:  When I get sessions in to mix & everything is recorded hot I gain individual tracks down so that the line ins on my console are not being overloaded. What mixer? What gain structure? By "gain individual tracks down", do you mean reducing the gain in the DAW? Quote:  I'm not sure if there are negative consequences if mixing ITB with tracks peaking at -6dBFS. DAW designers expect users to do so, so they have all sorts of trickery   built-in in order to cope with that. Quote:  But anyway, if the mic preamp sounds better at a higher gain setting then isn't the solution to calibrate the input of the AD converter to suit? In terms of noise performance, definitely yes. In terms of distortion, that may well be possible. In a fixed-topology preamp, distortion increases almost linearly with gain; that would advocate for the lowest possible gain. In fact it is important to make a distinction between gain and output level, although they are related. Again, in a fixed-topology preamp, increasing gain generally increases distortion (by reduction of gain-margin), and the related increase of output level (for a given input level) increases the distortion created in the output stage (except for crossover distortion). But it is also very possible that a certain balance of input/output distortion be particularly euphonic. This should be your particular operating level for the preamp, to which you should match the A/D converter's operating level. The presence of transformers in the signal path may also steer to a different conclusion.

Hi Geoff, I was not speaking generally, but specifically about my studio. And yes, the console is about 30 years old and I would definitely get undesirable distortion if I recorded all tracks peaking at -6dBFS. What I was getting at was that you have to consider how each piece of equipment integrates into the studio as a whole. Perhaps I could adjust the tape inputs on the desk so that they could accept higher levels from my DA converters (assuming that the DA converters themselves are fine with these levels), but then my analogue MTR will not be delivering the right level to the console. I also have to consider what levels the MTR & DAW will deliver directly to each other.

P.S. By "gain...down" I mean by using the Pro Tools Audiosuite 'Gain' plugin to reduce the level of tracks. I often see tracks that peak at 0dBFS. I think this is simply too much whether mixing ITB or out.

[Mark D.]

I don't mix analog. I will if engineering at a different studio, that has a desk. But I do up to 16 tracks recording, straight to the DAW from preamp's out. In this case -6db works. I have PT 8 but only use it with Digi Translator these days, to bounce files out as OMFs to use in Sonar. Each track in Sonar has an in and out control. I'll reduce one or both, unlike PT without a gain-reduction plug-in. I adjust for no clips, or intersample peaks, anywhere. At -6db peak recording, with those reductions, the result is no audible hiss even on the quietest parts. An -18db recording, track levels near zero or boosted, has a little more noise. If -6db had more noticeable distortion, I wouldn't do it. But -6db, with track level cuts as needed, has no extra distortion, and lower noise. Especially adding tracks together. If doing a board mix, you can always lower the input gain if that's a problem with individual tracks at that level going out of the DAW D/A to be mixed. This is the part I would hope to focus on even more. Mentioned above, A/Ds these days are prepared to get levels near 0db, so -6db input isn't a problem for them. I wonder if any thinks in general, despite recent advances dealing with it, they feel an A/D for some reason doesn't perform as well, or distorts more, at -6db per track vs. -18db.

Regarding a mic pre distorting more with more gain. When you get into mic pre land, again, you are looking at even some really high end preamps averaging 80-90db S/N with normal gain settings. If one lowers the gain -10db to -20db, you're getting only 60-80 db S/N. It's always best to operate a pre at its most optimal, of course. The best place between potential distortion and audible hiss at lower levels on quiet parts. But what I'd like to see is discussion, perhaps references and links as well to documentation, that a mic pre is noticeably distorting if the loudest input gain peaks are near 0db (ie. this would be -18db at the DAW if there is no added output volume). I don't notice anything bad, any distortion is minimal and useable. Of course, I would hear distortion at red peaks. But I'm talking infrequent yellow peaks here. 80-90% of the time in the green. Not going anywhere near 0db RMS. I know if a heavily compressed signal is mostly yellow most of the time, you'll hear it. I mean on vocal or acoustic guitar with a wide dynamic range, and lower RMS (-20 db or less) with just some yellow peaks, with a few rare peaks near red. It's how we've done it with analog for years. That seems reasonable, is one perhaps playing it too safe to think that is too 'hot' of a recording then?

[Geoff Emerick de Fake]

jetbase wrote on Mon, 17 May 2010 20:25

Perhaps I could adjust the tape inputs on the desk so that they could accept higher levels from my DA converters (assuming that the DA converters themselves are fine with these levels), but then my analogue MTR will not be delivering the right level to the console. I also have to consider what levels the MTR & DAW will deliver directly to each other.

Yes, I've seen several engineers transfering from tape to PT and back through their analog mixer just to get the levels right.

[Nick Sevilla]

I just finished an album mix, and used my 16 outputs from PT HD to my mixer, and Allen & Heath GL2800-32.

When I have a chance, I'll be listening to that album, and the one I mixed a year ago completely ITB.

I still go back and forth with the ITB / OTB thing. Since this album allowed me the time to set it up to do it OTB, I did it. The other album, did not, everything had to be done asap...

Cheers