{"id":24446,"date":"2011-08-28T15:24:59","date_gmt":"2011-08-28T22:24:59","guid":{"rendered":"http:\/\/9n2.ac0.myftpupload.com\/1313\/?p=3224"},"modified":"2011-08-28T15:24:59","modified_gmt":"2011-08-28T22:24:59","slug":"understanding-external-hardware-gain-staging-with-the-daw-in-mind","status":"publish","type":"post","link":"https:\/\/ericbeam.com\/?p=24446","title":{"rendered":"Hardware gain staging (with the DAW in mind)."},"content":{"rendered":"
For many when confronted with the terms dBFS, dBu, +4\/-10, VU, etc their eyes gloss over. Without understanding a few simple concepts, integrating your DAW with external hardware can be a game of trial & frustration.<\/p>\n
To properly drive & take full advantage of hardware in the analog realm, you need to 1st understand what\u00a0signal level the device is designed to receive. This is when dBu comes into play.<\/p>\n
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dBu – (dB in reference to 1 mW at 600 ohms, equal to 0.775 V)<\/span> All you really need to know is this is a\u00a0measurement standard for audio\u00a0signals.<\/li>\n<\/ul>\n
Most professional audio gear is made\/calibrated to function in a +4 dBu = 0VU environment. This means when a +4 dBu signal hits the hardware input, it will read 0 VU on the hardware’s VU meter.<\/p>\n
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VU – Unit of measurement originally developed in 1939 by the combined effort of Bell Labs and broadcasters CBS and NBC for measuring and standardizing the levels of telephone lines.<\/span><\/li>\n<\/ul>\n
The question that often comes up is “How do my DAW levels relate to my hardware?”<\/strong><\/p>\n
First off we need to know what level your audio interface is designed to output. For example, lets take a look at my mobile rig using a TC StudioKonnect 48. From checking the tech specs, I see the SK48 has a max output of +13 dBu. This means when my DAW software reads 0 dBFS peak, the SK48 is outputting\u00a0+13 dBu via the analog outputs.<\/p>\n
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dBFS – Decibels relative to full-scale.<\/span> (Digital full-scale) How most DAW\/Digital processors meter.<\/li>\n<\/ul>\n
To find out what level = 0 VU from of your DAW\/audio interface you can:<\/p>\n
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Patch into a piece of hardware you know to have properly calibrated VU meters. Send out a 1k tone until the VU meter reads 0 VU.<\/li>\n
(recommended method)<\/span> Get yourself a digital multimeter<\/strong> (DMM). 0 vu = 1.23 AC Volts RMS<\/span> (1.227 actually). Send out a 1k tone until the DMM reads 1.23 AC Volts RMS. (Measure the +\/- leads. Pins 2 & 3 of a xlr or tip & ring of a TRS connector) Keep note of the dBFS level that you’re sending out of your DAW. This dBFS level = 0 vu for your rig\/audio interface.<\/li>\n<\/ol>\n
For my TC SK48 I measured -9 dBFS in the DAW to equal 0 VU in the outside analog world.<\/p>\n
So what does this all mean? Well I now know that any signal\u00a0lingering\u00a0around -9 dBFS +\/- 10 dB from my TC\u00a0 is perfectly fine to interact with\u00a0typical\u00a0+4 dBu hardware inputs.<\/p>\n
Now lets think about headroom. We have established most hardware\u00a0devices will understand\u00a0 how to handle\/function in a +4 dBu environment. But still every hardware device will have its own maximum signal it can receive\/output. This means every device will have a different amount of headroom over 0 VU.<\/p>\n
My TC interface has a maximum output of\u00a0 +13 dBu, & my Lynx converters have a maximum of +20 dBu. The Lynx outputs 0 VU at -16 dBFS (via the DAW), this works out to make the Lynx have\u00a0 7 dBu more headroom over 0 VU then the TC interface. Is this better? Potentially, but in most scenarios no. It is only useful if you’re trying to send a hotter signal to a device without input\/output gain control.<\/p>\n
Lets go over inputs. All hardware will have a dBu spec for its inputs as well. The device will usually have a matching dBu spec for both its inputs\/outputs. For example my TC interface can handle a +13 dBu signal at its input without the pad engaged. If you created a loop, whatever you send out of the TC will be the same dBFS level coming back into the TC.<\/p>\n
Now say you wanted to send a 0 VU signal from the TC & return via the Lynx converter. As previously calculated I need to send a -9 dBFS signal from my TC\/DAW to = 0 VU. Because the Lynx is a +20 dBu device this will not return as -9 dBFS in the DAW. It will come back as -16 dBFS. You would have to add 7 dB of gain to match the original dBFS level.<\/p>\n
Now for some real world examples –<\/p>\n
Say I want to compress a signal from my TC\/DAW, into a 1176, & back into my DAW via my API-A2D converters. The 1176 will operate fine with a signal from my TC, being that both are made to function in a +4 dBu\u00a0= o VU environment. But I also know that my API-A2D converter has a +18 dBu maximum input rating. With The TC being a +13 device, I will have to gain the output up +5 dBu to equal the same dBFS level on the return into the DAW. It’s all simple math.<\/p>\n
One final thing that should be noted is country-based reference standards. In the US, -20 dBFS = 0 VU \/\u00a0 in Europe, – 18 dBFS = 0 VU. If you wanted to calibrate your DAW\/studio to function at this calibration, you will have to have -\/+ trim ability on your audio interface\/converters.\u00a0 This works out to be +24 dBu for US & +22 dBu for EU. For example, if I wanted to calibrate my TC based studio to have -20 dBFS = 0 VU, I would have to externally trim my +13 dBu outputs +11 dB & attenuate my inputs -11 dB to function at this calibration. I would have to build a line level amplifier for my i\/o. More realistically, I would just trim my DAW session down -11 dB if I wanted to process my session setting in a -20 calibrated studio.\u00a0 Unless you’re wanting to transfer sessions & outboard settings with other studios, this is unnecessary. You’re better off calibrating your studio based on your interface.<\/p>\n
With this information you should be able to figure out how to drive your outboard\/console from your DAW with proper gain staging.<\/p>\n
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