Studer 089 Racking Job advice

[bluespills]

Hello,
this is one of my first DIY projects (besides some kits where everything is pretty much done for you) so please bear with me. 
I'm racking 2 mono input channels from the studer 089 (1.090.017) , and using the 089 dual line amp (1.091.035) for the output.  I will order probably a silent arts kit for PSU. 
I am posting here a diagram of how i planned to connect them, but please if you see a mistake or a better way of doing it, advice is very appreciated!

My plan was to use the reverb send as the output, so that would act as an output attenuator. 
The output of the input module is unbalanced, and the input of the line amp is balanced, so i hope i connected these correctly.

Anyways,i thought i would post this before i start and hopefully avoid some mistakes. 

cheers
Zack

 

[bluespills]

dual line amp schematic

 

[bluespills]

input module schematic

 

[moamps]

I can't open your attachments, but have manual for 089 console. Your wiring looks ok. Just to add that you should be careful with PS wiring, + pole is connected to the common/ground.

 

[bluespills]

Thanks! do you mean like this?

I can't open your attachments, but have manual for 089 console. Your wiring looks ok. Just to add that you should be careful with PS wiring, + pole is connected to the common/ground.

 

[moamps]

Blue, negative and black wires are ok, but red (positive) you should left unconnected. These modules need only single voltage so on the PS which provides a dual voltage, you may left the positive part unpopulated.

 

[bluespills]

Great, thanks! 
Someone suggested to me to not use the Reverb send knob as output into the line amp.  Instead, go from the fader output pins and replace the fader with a rotary potentiometer.  Do you see any advantage to do that?  Isn't it just the same to use the rev 1 out, and use the knob thats already there on the channel?

Blue, negative and black wires are ok, but red (positive) you should left unconnected. These modules need only single voltage so on the PS which provides a dual voltage, you may left the positive part unpopulated.

 

[moamps]

Someone suggested to me to not use the Reverb send knob as output into the line amp.  Instead, go from the fader output pins and replace the fader with a rotary potentiometer.  Do you see any advantage to do that?  Isn't it just the same to use the rev 1 out, and use the knob thats already there on the channel?

You are correct. All outputs (main, rev1 and rev2) use identical buffer so there should not be any difference.

 

[zamproject]

All outputs (main, rev1 and rev2) use identical buffer so there should not be any difference.

Hi

No ! fader buffer (main path) have the usual 10dB gain, which is not the case for aux output.
Also with aux, you wont be able to use insert if set pre fader, and you will have two buffer if set after fader, which is not necessary.

I suggest to use one of the aux pot but rewired as fader replacement (let say rev1).
You can still connect rev 2 for a parallel output, unbalanced mono jack. It's an easy to do option, and maybe one day you'll be happy to have it, like driving a side chain input at a comp or whatever.

Best
Zam

 

[moamps]

No ! fader buffer (main path) have the usual 10dB gain, which is not the case for aux output.

I found several times during the racking of this type of modules that this gain is not needed because of high available gain in the output card-amp. I will never suggest to use an amplifier if you will need to attenuate it's gain in the next stage. But YMMV. Also, as you already know, the headroom of this modules isn't so high so you should be very careful with gains in the whole signal path.

Also with aux, you wont be able to use insert if set pre fader, and you will have two buffer if set after fader, which is not necessary.

Zack didn't ask anything about the insert.

 

[zamproject]

I found several times during the racking of this type of modules that this gain is not needed because of high available gain in the output card-amp. I will never suggest to use an amplifier if you will need to attenuate it's gain in the next stage. But YMMV. Also, as you already know, the headroom of this modules isn't so high so you should be very careful with gains in the whole signal path.

Zack didn't ask anything about the insert.

Hello

Not using the fader buffer (in fact 16dB to also recover extra 6dB from preamp/eq stage) make the nominal level -25dBu post fader module output, of course then the head room is 49dB post fader!!! But, line amp card do 30dB max gain, you won't be able to set a proper in to out unity gain without pushing the line gain trim setup at preamp stage, which reduce headroom at this step.
It's a whole pass as you say
There is reason Studer design them like this.

Best
Zam

 

[moamps]

The nominal output of Rev1,2 outs is -25dBu, so with 30dB gain of the line amp this is +5dBu at final output. The nominal output level is usually +4dBu so I don't see how the proper gain can't be set without trimming gain in the input stage.
As I said, I had never problems with insufficient gain of this setup so I will stop now to discuss it further. If Zack needs more help from me, he can PM me.

 

[zamproject]

The nominal output of Rev1,2 outs is -25dBu, so with 30dB gain of the line amp this is +5dBu at final output. The nominal output level is usually +4dBu so I don't see how the proper gain can't be set without trimming gain in the input stage.
As I said, I had never problems with insufficient gain of this setup so I will stop now to discuss it further. If Zack needs more help from me, he can PM me.

Hi

Please the discussion is interesting.
+4dBu is not a line level !
If you set up for +6PPM, which is the low side, your proposition will work with only 1dB to catch at internal trim line calibration at module, internal gain and unity from in to out will be ok, I agree, but maybe full gain at line out card won't be the better S/N choices.
For a proper "+4dBu" output (which is Vu specification) your line level is +12dBu, you won't catch this without over trimming the calibration pot at the line in preamp (and dramatically add noise and reduce headroom at filter and EQ), also S/N will not be good  :-\
Maybe not relevant for one channels ? I don't know, never use racked modules.

But now i'm thinking maybe you count without fader -10dB nominal position (even if we replace with a pot), If with your racking signal flow you consider unity with pot full on ? then you have extra 10dB that may explain your observations.

Best
Zam

 

[bluespills]

Hello, and thank you guys for your input!  I appreciate it.  I took a look at the schematics and it says...
Main output normal level -  U norm 280mV (with master fader at 10db)
    Maximum Ouput - U max 5v
Reverb normal output level  45mV
  Maximum -  4v

looking at the schematics the output buffers look to be identical so thats why i thought it shouldn't matter which to use. 
but if the output level ratings are true, then it seems the main output would be a bit more gain, but the question is because it says "with fader at 10db"...where is the reverb pot at to get 45mV?

Maybe i need to try both and see. 

@Zam,  if i understand you correct, did you mean to disconnect the original wiring from the Rev potentiometer, and wire it where the fader would be, then go out from the regular "output" pin. 

 

[zamproject]

Hello, and thank you guys for your input!  I appreciate it.  I took a look at the schematics and it says...
Main output normal level -  U norm 280mV (with master fader at 10db)
    Maximum Ouput - U max 5v
Reverb normal output level  45mV
  Maximum -  4v

looking at the schematics the output buffers look to be identical so thats why i thought it shouldn't matter which to use. 
but if the output level ratings are true, then it seems the main output would be a bit more gain, but the question is because it says "with fader at 10db"...where is the reverb pot at to get 45mV?

NO ! look at NFB, the gain is not the same
-Main have 16dB boost to compensate 10dB (attenuation) nominal fader position, + 6dB for previous attenuation in the chain
-Aux have unity gain for output buffer, the extra level is given by the sum amp before reaching Aux line out in real desk.

From experience in my desk I usually set Aux pots aroud 6 or 7 when calibrating to have the -10dB nominal setting (and margin) at Aux send (same for Aux master)
So just consider your Aux pot (log audio in this case) like a fader, with 10dB attenuation @ first quarter

Maybe i need to try both and see. 

Yes 

@Zam,  if i understand you correct, did you mean to disconnect the original wiring from the Rev potentiometer, and wire it where the fader would be, then go out from the regular "output" pin.

Yes it is.

Best
Zam

 

[bluespills]

Alright, I'm going to to try using the main output.  But now I also got thinking about the impedance matching between the input unit and dual line amp.  I bought the units separate so I don't know if these dual line amps were used in the mk1 consoles. here is the info from the manual.  Do i have something to worry about regarding impedance?  (i am sorry in advance if these are really basic questions!,  I am a newb but I am eager to learn

input unit  1.090.017
1. Main Output
U norm -  280mV
Max output Voltage - 5v
source impedance at 1kHz - Zs < 2 ohms
Load Impedance  ZL > 1k Ohm

5.1 Reverb outputs
Unorm 45mV
Max voltage 4v
Source impedance  50 ohms
load impedance 1k Ohms

DUAL LINE AMP 1.091.035
Input
differential >10k oHm
single ended > 5k ohm