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Yamaha N12: modding line in to bypass preamp?
Old 20th January 2013
  #1
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ben_allison's Avatar
 
🎧 15 years
Question Yamaha N12: modding line in to bypass preamp?

The Yamaha N12 seems like a neat mixer, with pretty respectable conversion... one thing that bugs me is that the line ins go through the preamps. This is a bummer if you want to use external pres.

Looking at the block diagram, it seems like the pres go right to the A/D stage.

Any ideas if there would be an easy mod so that the line ins bypass the pres?
Old 21st January 2013
  #2
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nyfrequencies's Avatar
 
🎧 15 years
Fill me in if you get any feedback.
Old 21st January 2013 | Show parent
  #3
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ben_allison's Avatar
 
🎧 15 years
Quote:
Originally Posted by nyfrequencies ➑️
Fill me in if you get any feedback.
I feel like it could be as simple as cutting a lead on the board, and adding a jumper... but I could be wrong!
Old 21st January 2013 | Show parent
  #4
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Richard Crowley's Avatar
 
🎧 10 years
Quote:
Originally Posted by ben_allison ➑️
I feel like it could be as simple as cutting a lead on the board, and adding a jumper... but I could be wrong!
That seems like a live possibility. Do you have the schematic diagram of the circuit?
Old 21st January 2013
  #5
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ben_allison's Avatar
 
🎧 15 years
Was able to find some schems from a repair manual.

These show where the input connects to the board.
Attached Files
File Type: pdf yamaha_n8_n12 (dragged).pdf (1.22 MB, 432 views)
Old 21st January 2013
  #6
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ben_allison's Avatar
 
🎧 15 years
And some board layouts...
Attached Files
File Type: pdf yamaha_n8_n12-board.pdf (3.09 MB, 365 views)
Old 21st January 2013
  #7
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🎧 10 years
Quote:
The Yamaha N12 seems like a neat mixer, with pretty respI'ective conversion... one thing that bugs me is that the line ins go through the preamps. This is a bummer if you want to use external pres.
have you even measured it????

they complained about this "problem" with a behringer ada8000 till they realized it did absolutely nothing to the signal when the knob was down. Which is exactly like you would use it with external preamps.

most low end mixer input topology today add minimal derogation to the signal using external preamps. It's the fact that the one knob is GAIN and when it's down it has nearly zero effect on the line input if it does it's proably broken!
Old 22nd January 2013 | Show parent
  #8
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ben_allison's Avatar
 
🎧 15 years
Quote:
Originally Posted by doulos30 ➑️
have you even measured it????

they complained about this "problem" with a behringer ada8000 till they realized it did absolutely nothing to the signal when the knob was down. Which is exactly like you would use it with external preamps.

most low end mixer input topology today add minimal derogation to the signal using external preamps. It's the fact that the one knob is GAIN and when it's down it has nearly zero effect on the line input if it does it's proably broken!
I haven't measured it... it would be interesting to try and determine if anything whatsoever happens with the gain at 0.
Old 22nd January 2013 | Show parent
  #9
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Richard Crowley's Avatar
 
🎧 10 years
Quote:
Originally Posted by ben_allison ➑️
Was able to find some schems from a repair manual.

These show where the input connects to the board.
The image is too fuzzy to read the resistor values, but it looks like the signal is already balanced more-or-less "line level" at the point where it enters that board. Presumably there are other stages of audio previous to this point in the circuit. There doesn't appear to be much gain in those op-amp circuits.
Old 22nd January 2013
  #10
Lives for gear
 
🎧 15 years
Hi
Using the insert return jack, unfortunately unbalanced should be relatively 'clean'. Hijacking the balanced interconnect from the mic amp/insert board at the link connector to the A/D board would get a slightly 'cleaner' signal, about as good as it could be without further redesign. BUT there is no RF or other filtering available on board if you were to use this as an input. It would definately work but MAY suffer interference depending on how it is fed, which should of course be balanced.
Mr Jensen of the transformers would suggest you pull the op amp at the input to the A/D chip and fit one of his transformers (per channel of course!). There is an application note about doing this with a 'Crystal Semi' A/D chip.
Matt S
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