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Post by levon on Sept 21, 2016 23:55:23 GMT -6
Need some help with the metering in Logic. I'm not a pro engineer and I tried to wrap my head around the metering subject for years without much success. So maybe someone can explain in plain terms how analog metering and calibration translates to Logic Pro..??.. Imagine you need to explain this to a 6-year old.  In my case, I need to calibrate my Dolby 361 unit that I want to use as a vocal stressor. You know, that old 70s trick to send a vocal through a dolby unit, encode and return it to the desk without decoding it. I remember engineers in the 80s doing it but I never paid much attention to what they did back then. It just sounded great and that was enough. I have a modded Cat22 card that allows me to do that, but that requires calibration of the unit. The instructions say that this is based on +4db=0vu. Now, that's all fine, but which level does that equal in Logic Pro? I also need to trim the Dolby output to show -7vu, again, what does that correspond to in Logic Pro? The input to the Dolby needs to calibrated with a sine wave generator set to 1KHz at 0vu/+4db. Logic has a generator that I can set to 1Khz, and it shows 0db on the Logic metering scale. But, does that equal +4db in the analog world?? I'm sure it doesn't. I'm grateful for any help on this confusing subject as I have no freaking clue and I'm pretty much lost... |
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Post by pope on Sept 22, 2016 2:45:23 GMT -6
I'm sure that someone we'll explain this better than me, but there you go: What interface are you using? Logic (and all DAWs) will display the dBFS (Full scale) value. 0dBfs is equal to the maximum dBu value (that your interface supports) before the converters clip. There is not standart value of how many dBu the interface "accepts" before clipping (i.e headroom). In other words, some interfaces will be 0dBfs= +18dBu, other 0dbfs= +22dBu, and so on. So for example the manual of your if your interface states 0dbFS= +20dBu, it means that when you read -20dB in Logic, you are at 0dBu in the analog domain. Hope this makes some sense…  |
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Post by levon on Sept 22, 2016 3:17:06 GMT -6
I go through Apogee Rosetta converters into an Apogee Symphony PCIe card, if that's what you mean by interface...??..
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Post by pope on Sept 22, 2016 3:26:50 GMT -6
Yes, read the apogee manual. It should state what level the converters are calibrated at. If it's at -20dBFS, that means that when you read -20dB in Logic, your level is +4dBu. That's just an example.
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Post by levon on Sept 22, 2016 3:34:06 GMT -6
Ok, thanks, that makes it a lot clearer. The Rosettas have jumpers for 3 different settings, I never bothered to check the jumper settings in my Rosettas, anybody has an idea what the default factory setting is?
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Post by levon on Sept 22, 2016 3:39:10 GMT -6
The manual for the Rosetta 200 says that it is calibrated to the default level of +4 dBu = -16 dBFs. I suppose the 800s have the same calibration.
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Post by chasmanian on Sept 22, 2016 3:42:47 GMT -6
levon, I know less than you about the actual details and mechanisms for this subject. I apologize if any of this is wrong or simply not helpful. that said, only in an effort to help, I googled and found a couple things. the first link is to a review for the Rosetta, it says: "The rear panel of the Rosetta 200 carries balanced line-level analogue inputs and outputs on XLRs, adjustable for peak levels anywhere between +2dBu and +26dBu." www.soundonsound.com/reviews/apogee-rosetta-200the second link is for the the 200 model. page 6 (bottom....item 14)) shows Calibration steps. page 11 Features and Specs shows Analog max levels: adjustable between +2 dBu and +26 dBu. www.apogeedigital.com/pdf/rosetta200_usersguide.pdf |
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Post by levon on Sept 22, 2016 3:47:51 GMT -6
Chas, thanks, everything helps. Thanks also Pope, You guys rock. I have checked the manuals, the 200 manual says that the default calibration level is +4 dBu = -16 dBFs. The 800 manual doesn't mention any default setting. As I said, being ignorant, I never opened my units and checked. Guess I'll have to tear my rack apart and have a look after all.
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Post by levon on Sept 22, 2016 3:57:53 GMT -6
At least now I know that the Apogees determine the metering in Logic. Never occurred to me. Goes to show how great a noob I still am  |
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Post by kilroyrock on Sept 22, 2016 6:19:47 GMT -6
I'm sure that someone we'll explain this better than me, but there you go: What interface are you using? Logic (and all DAWs) will display the dBFS (Full scale) value. 0dBfs is equal to the maximum dBu value (that your interface supports) before the converters clip. There is not standart value of how many dBu the interface "accepts" before clipping (i.e headroom). In other words, some interfaces will be 0dBfs= +18dBu, other 0dbfs= +22dBu, and so on. So for example the manual of your if your interface states 0dbFS= +20dBu, it means that when you read -20dB in Logic, you are at 0dBu in the analog domain. Hope this makes some sense… 23 posts into Real Gear Online and you've already opened my eyes to what I didn't realize! Welcome to RGO! |
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Post by swurveman on Sept 22, 2016 7:25:56 GMT -6
"The rear panel of the Rosetta 200 carries balanced line-level analogue inputs and outputs on XLRs, adjustable for peak levels anywhere between +2dBu and +26dBu." Hey chasmanian, Here's some question I wonder about when it comes to converters. Perhaps you have an answer. Perhaps others will. Converters have a "nominal level", which if I understand it correctly means that the best signal quality is obtained when the meter rarely goes above nominal.. Typically that's +4 dBu. So, if a converter is pushed past it's nominal level the quality is not "the best" as defined by the manufacturer. But in converters, what does that mean? All of these converters have headroom-if that's the right term. My Aurora 16's are +4 dBu nominal, but can go up to +20 dBu before they clip. So, why do they determine a nominal/best level and then have levels far above it? |
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ericn
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Post by ericn on Sept 22, 2016 8:19:20 GMT -6
I'm sure that someone we'll explain this better than me, but there you go: What interface are you using? Logic (and all DAWs) will display the dBFS (Full scale) value. 0dBfs is equal to the maximum dBu value (that your interface supports) before the converters clip. There is not standart value of how many dBu the interface "accepts" before clipping (i.e headroom). In other words, some interfaces will be 0dBfs= +18dBu, other 0dbfs= +22dBu, and so on. So for example the manual of your if your interface states 0dbFS= +20dBu, it means that when you read -20dB in Logic, you are at 0dBu in the analog domain. Hope this makes some sense… Great post but it needs some clarification , and a big in theory and is supposed to! A big factor is also how your converter is interfaced. If your actual converter is connected via a dumb interface i.e.MADI, AES, SPIF your metering is going to be set for the device connected to the bus . |
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Post by levon on Sept 22, 2016 8:28:42 GMT -6
The Rosettas are connected to an Apogee Symphony PCIe card in my Mac.
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Post by Martin John Butler on Sept 22, 2016 8:37:44 GMT -6
Logic user here. I've always wished there was a way to recalibrate Logic's metering. One you've established what level equals analogue zero, it would be great if the meters corresponded. Same way you have options to view things, why not have an option to "analogize" your metering?
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Post by popmann on Sept 22, 2016 8:53:04 GMT -6
According to a Mix mag review, the default is -16dbfs=+4vu. YMMV, but for sure the three jumper settings are -20, -16, and -10.
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Post by popmann on Sept 22, 2016 9:03:13 GMT -6
The only thing that can change about Logic's (DAW's) metering is where yellow and red start. Right? You DO want a digital meter showing you full scale levels. So, you because of the way it's graduated (non linear)….to set -18=red would mean there's nearly no green. I would suggest they simply are tell you two different things….and if you set it to -16 to -4dbfs = yellow, that now tell you not much….so, to model a VU best, you'd set -20 to -16dbfs at yellow and everything above -16dbfs as red….is that really more useful? I suppose if you're using them to set input levels, yes--maybe….. That should be changeable…..note the DATE on this article: www.soundonsound.com/techniques/level-meters?print=yes |
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Post by chasmanian on Sept 22, 2016 9:43:30 GMT -6
Hey swurveman, I do not know much about this stuff.
Even so, I'll pm you.
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Post by drbill on Sept 22, 2016 11:18:14 GMT -6
FORGET the metering in Logic. No DAW really has accurate enough metering to calibrate analog gear easily. Use your DMM to measure voltage at your D/A and at the output of your Dolby card. Simple, and accurate. +4dBu = 1.23 volts -7dBu = 0.35 volts wait, I'm unsure if you need -7dBu or -7 on the VU meter with 0vu being calibrated to +4. If the latter you need -3dBu which is 0.55 volts. Where is jim williams when we need him.....  |
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Post by levon on Sept 22, 2016 22:54:42 GMT -6
According to a Mix mag review, the default is -16dbfs=+4vu. YMMV, but for sure the three jumper settings are -20, -16, and -10. You're right, I opened up my units and they were set to -16dbfs=+4vu. Except a spare one that I bought a couple of months ago that had 2 of the output channels set to -20dbfs=+4vu. Weird. |
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Post by popmann on Sept 23, 2016 9:15:40 GMT -6
Well--they DO it per channel so that you CAN calibrate all the hardware in your studio to THEIR proper levels. In fact, the "bigger" 16x series has trim pots so you can dial it in exactly for an installation of all kinds of mismatched gear. I feel like they've changed that to software control with Symphony....which is one of the things that turned me off....
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Post by ChaseUTB on Sept 24, 2016 7:44:20 GMT -6
I'm logic preferences you can change the meter from linear to exponential, other logic users say it helps them keep healthy consistent levels where's normally their levels would be too hot. Also logic had pre / post fader metering so look into that as well. Link is to a help thread for logic and includes a vid. Hope this helps www.logicprohelp.com/forum/viewtopic.php?t=101688 |
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