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Old 02-07-2017, 10:02 AM   #1
metal_priest
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Default understanding focusrite preamp gain steps in db

ok, I know..maybe this could seem a wierd question but I really need to understand this.

I have a liquid saffire 56 and a octopre mkII both by Focusrite. I'm happy with them (ok, when I can use a couple of Millennia instead I'm more happy, but you know...they cost a lot and not always you have the budget to rent them...) but there's this silly thing I can't figure it out: what's the gain step in db for the preamp section.
They labeled the pot with an useless 0to10 scale and in the specification they say the db gain range is 13db to 60db.



Ok, so? how can I know how many db of gain I have when my pot is on "7"?
If I make some recording for another guy and I have to tell him how much gain was on the preamp i cannot say "it was on 7"! Or for a tomorrow remix of a job, if i wrote in project notes "gain at 8.5" it will mean anything if i will not have this setup anymore!

So, my question is: should I simply divide 47 (difference between 60 and 13) into 10 parts? This way I will gain with commas like 20,05db or 52,95...not so easy to calculate when you're on a stage!
Maybe the scale is logarithmic because it's about db? ok, my math in this case fails and I'm not sure I know how to calculate the steps...


To make things more complicated, the octopre and LS56 has a different gain range..one it's 10 to 55 and one it's 13 to 60...
with the octopre (10 to 55) the scale divided by 10 has a meaning because the steps are each 4.5db, but that LS56 range is really uncomfortable

EDIT: MAYBE THIS TOPIC CAN BE MOVED TO THE RECORDING TECHNOLOGIES SECTION, SORRY
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Old 02-07-2017, 03:07 PM   #2
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Yeah it's probably not that easy. The only real way to know is to test: Record a repeatable impulse at minimum gain, then turn it to 7 and record the exact same thing again, then do some simple math.

Not sure why it matters once it's recorded. I suppose if you want to record again on the same setup, it might help, but if you're just handing somebody a .wav file, why do they care where the gain knob was set? The get what they get and deal with it as necessary.
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Old 02-07-2017, 04:06 PM   #3
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On my iPhone I have an ap called Signal Generator from http://mediapunkstudios.com/. With that I can get repeatable signals with 0.1 dB resolution. If I need to get an exact setting with my gain control I can use that.
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Old 02-08-2017, 12:12 AM   #4
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thank you guys, i was afraid I should spend some time testing and I was hoping it wasn't necessary...i don't have an iphone but i will get a signal generator and make some test.

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Not sure why it matters once it's recorded. I suppose if you want to record again on the same setup, it might help, but if you're just handing somebody a .wav file, why do they care where the gain knob was set? The get what they get and deal with it as necessary.
It's quite important, at least for my job in classical music, to record all the stuff you used to record something...all the setup including cables model and lenght (I'm serious) has to be noted because usually classical musicians are really pedantic! So it's a way to live better

Jokes apart, you need to note the gain levels also for the post-production because it could happen you change some level during the recording and of course you need to compensate the difference in post-production...it's more easy if you have fixed gain stages to deal with. Also, if you need to re-record something one day but you don't have the same setting (different mic or different amp) at least you can have the same gain, and if you use different mics that have different sensitivity you can compensate it with a slighty different gain on the preamp to have the same final level.
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Old 02-13-2017, 02:11 AM   #5
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Ok, so..just for the records I report here what I've tested:

the pots are logarithmic so for the first half the increase of gain it's really small. On the other hand, in the second half you have around 10 db for each steps, that's why it's really difficult to be precise when you set the levels...

so, approximately these are the steps (for the second half):

pot 6 --- gain +25
pot 7 --- gain +30
pot 8 --- gain +40
pot 9 --- gain +50
pot 10 --- gain +60
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Old 02-13-2017, 04:56 AM   #6
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yeah, many other Focusrite units with these kind of knobs are the same.
At least the ISA preamp knobs do what they are labeled with, but they are several times more pricey
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Old 02-20-2017, 03:52 PM   #7
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I hear you with the 0-10 gain knobs, it makes the things seem a bit "toytown" and I've taken them to task about it before.

The dB gain increments you've worked out are quite reasonable and useful steps by the looks of it.




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Old 02-23-2017, 11:26 AM   #8
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exactly planetnine, i find little bit wierd and kinda "unprofessional" this 0to10 gain, I want to know how much gain I'm using...anyway, this approximate levels I calculate should be useful at least to understand the range...it's still "impossible" to know how many db you add or subtract if you change a bit the levels during the recording, but for now I can accept it.
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Old 02-23-2017, 11:29 AM   #9
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If it helps any my API preamps (left) only has dots, no numbers or dB markings. My Neve 511 (center) has dB markings but my as pro A-Designs P1 (right) has only dots, just a big knob so in reality, not sure it truly matters in the real world - meaning professional isn't necessarily the difference here...

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Old 02-23-2017, 04:23 PM   #10
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yes, of course...in fact I wrote it with inverted commas! As I said, all depends on the kind of works you usually do...I work with classical music and musicians, with very meticulous artistic producers and not being able to say how much gain you're using can be seen as "unprofessional".
Luckly I have easy access to both Millennia HV-3D and HV-3R or Antelope MP32 for as many channels i need, but for the smallest (and low budget) jobs I'd like to use these Focusrite gear and I was trying to have the same workflow and precision I have with Millennia or MP32
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Old 02-23-2017, 07:33 PM   #11
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Yea, I get it. It's not like I'd be upset if they all had them.
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Old 02-26-2017, 12:52 AM   #12
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It's like a certain DAW I use doesn't have dB marks on its faders...




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