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#1
11th February 2013
11th February 2013
#1
Lives for gear

Joined: Apr 2011
Location: Vermont
Posts: 2,916
My Recordings/Credits

Logic bus levels

why is there a difference in level when using the 'send' vs. the channel 'output' slot when routing something to a bus?
shouldn't they be the same...?
ex...
say i have a source track/channel with 0 dBFS signal...
if i route to a bus via the send knob and attenuate -10 dB with the 'knob' or the track fader, the level is -10.21 dB at the bus.
if i route to the bus from the channel output and use the fader to attenuate -10 dB, the level is -10 dB at the bus.

(*values entered via text box)

edit: attached pics to show routing
pic 1 > bus send @ -10dB
pic 2 > fader @ -10dB, output to bus
Attached Thumbnails

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DC, San Antone and the Liberty Town, Boston and Baton Rouge, Tulsa, Austin, Oklahoma City, Seattle, San Francisco, too...
lovespirals
#2
11th February 2013
11th February 2013
#2
Gear maniac

Joined: Jul 2007
Location: Los Angeles
Posts: 192

wow. eagle eye. i've never noticed that one before.
#3
12th February 2013
12th February 2013
#3
Gear maniac

Joined: Sep 2011
Posts: 289

#4
12th February 2013
12th February 2013
#4
Lives for gear

Joined: Apr 2011
Location: Vermont
Posts: 2,916
My Recordings/Credits

you can choose pre/post for the send. i checked both ways and the results are the same.

what is even stranger is that if you use a value of -6dB (instead of -10dB) then the fader and the bus send are the same...
-6dB on the fader = -6dB on the bus send
(*each give an actual value of -5.92dB)
#5
12th February 2013
12th February 2013
#5
Lives for gear

Joined: Aug 2010
Posts: 4,019

Do you have the master fader at 0dB? I don't mean the the main output that is usually to output 1-2. I mean the fader on the far right in the mixer tab.

Edit: tested with Logic test oscillator and I don't get any difference in levels. It's perfect here.

Re-edit: I hadn't tried like you did. I do see a difference in level now.
#6
12th February 2013
12th February 2013
#6
Lives for gear

Joined: Apr 2011
Location: Vermont
Posts: 2,916
My Recordings/Credits

yes, the master is @ 0.

(imo) it should be the same level regardless of how it's routed...
i don't understand why it's like this.
valis
#7
12th February 2013
12th February 2013
#7
Lives for gear

Joined: Apr 2006
Location: Northwest USA
Posts: 4,563

Interface values quantize the available resolution, much like an automation related thread found on this forum.
#8
12th February 2013
12th February 2013
#8
Lives for gear

Joined: Apr 2011
Location: Vermont
Posts: 2,916
My Recordings/Credits

^ i thought that was the issue with the discrepancy between GUI values and actual values...
but why do the values change depending on how they are routed...?
valis
#9
13th February 2013
13th February 2013
#9
Lives for gear

Joined: Apr 2006
Location: Northwest USA
Posts: 4,563

They're not, you're setting the level on a send in one case and the channel fader in another. Apparently the send knob has a small rounding "difference" compared to the fader.

This *exact* case was mentioned in another thread before, not sure if it was the thread I referenced previously or not offhand...
#10
16th February 2013
16th February 2013
#10
Gear maniac

Joined: Jul 2006
Location: Sweden
Posts: 151

Remember that Logic uses 7-bit accuracy for sends.
The Channel Strip Volume is 10-bit.

You can easily check this in the automation header.
View automation for your send and you will see that the value actually is -10.2 which will match the 10.21 dB of attenuation.
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Logic Pro 9.1.8
RME Fireface UFX

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