Calrec pq1549 pin outs

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Skintologist

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Jan 29, 2012
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I just bought a pair of pq1549 modules and had wrongly assumed that the pins would match those of a faulty pq1785 that I wanted to replace in a "lunchbox".
  The schematic on this site provides some information but no clue as to which of the two connectors the various pin numbers refer to.
  Can anyone help with how to wire them up?
 
I've gotten most of the way but am missing how to wire up the L switch, which I presume select the line input? Calrec had said Pin 3 on Board B "Ground to fire", but I'm not sure what that means. The L switch connects to pins 1-3 on the A Board, but I have no info how to proceed. Does anyone have the schematics to the A Board, the EQ section Schematic on the Gyraf page is missing bits.

There seems to be someone in the blackmarket with them for sale who has schematics, but I don't seem to be able to message them or reply in the thread. Could anyone help?
 
I'm doing the same at the moment, I thought the Gyraf schematic cover the whole module as well. The other board seems to be the mic input and logic circuits. Are you talking about the person in Australia who has modules for sale? I bought mine from them so I might see if they have them, I'd imagine Gyraf has them for sure also.
What have you figured out so far? It looks like you just need to bridge the different sections together. I've run signal through the EQ section and it sounds good but it is difficult to figure out the other connections.
 
phetus said:
Calrec had said Pin 3 on Board B "Ground to fire", but I'm not sure what that means.
Click to expand...
Ok, figured it out. Grounding Pin 3 Line Select triggers the relay to switch from Mic to Line on pins 5 and 7 respectively. Pin 2 on the EQ board should be grounded somewhere and Pin 3 on each board should be connected together.
 
So I've got most of this figured out but I'm stumped on how the EQ switch is supposed to work, which I assumed was a bypass. The schematic suggests that Pin 27 connects to Pin 24 at the EQ input so the EQ switch just switches the signals on Pins 28 and 29 to the EQ. Anyone know how the switch is actually supposed to work?
 
IIRC the "EQ" marked switch on the calrec channel eq module was for the HP/LP filters: Pressed, filters follow EQ - alternative is "DYN", where filters were assigned to dynamics sidechain (e.g. noisegate keying)

Here comes, attached, what I have on it:
 

Attachments

  • CALREC PQ1549 manual scan.pdf
    565 KB · Views: 3
I would highly recommend not making the mistake I made and try and sus things out with the backplane, which, when not actually in the console, has no keying to prevent you from putting the module in upside down. I cannot begin to fathom how much time I wasted trying to understand why things were linked the way they were.
 
gyraf said:
IIRC the "EQ" marked switch on the calrec channel eq module was for the HP/LP filters: Pressed, filters follow EQ - alternative is "DYN", where filters were assigned to dynamics sidechain (e.g. noisegate keying)

Here comes, attached, what I have on it:
Click to expand...

In playing with the module, I can definitely confirm this. I also found this brochure that gives a decent amount of information.

Jakob- If I wanted to create an insert point between the pre and eq, or a bypass for the eq section (with a relay maybe??) would the input/output amps from your clone be suitable? I have the transformers to make the 1520 output amp, but not two per channel.......... I would use the in/out buffer from your design on the pre output and eq input to give me a balanced insert point and then use the 1520 at the end. Insert switch would activate send and return between the pre and eq, and eq bypass would send the output of the preamp to the 1520. Am I too ambitious??
 
Remember the internal oerating level of all calrec desks is between -6 to -14db LESS than the nominal line input level. Many modules have level setting pins so that they would take 'instruction' from the motherboard to act at -10, -12 or -14dB internally. Failing to compensate for this will mean that you have to push the input gain and then run out of headroom. the SYSTEM was designed to allow around +24dBu headroom throughout for the complete desk.Animals that don't respect this will experience disappointment
 
Matt Syson said:
Remember the internal oerating level of all calrec desks is between -6 to -14db LESS than the nominal line input level. Many modules have level setting pins so that they would take 'instruction' from the motherboard to act at -10, -12 or -14dB internally. Failing to compensate for this will mean that you have to push the input gain and then run out of headroom. the SYSTEM was designed to allow around +24dBu headroom throughout for the complete desk.Animals that don't respect this will experience disappointment
Click to expand...

I'm aware of this and have also caught that all the pins were shorted together on the backplane PCB. Not sure where that leaves me in operating level though- that part is sort of unclear to me because com isn't labelled
gyraf said:
could be done - but you don't need balanced send for your insert, just use impedance balanced
Click to expand...
I *think* I understand how to do this- just a resistor on the cold output to signal ground? Not sure how to get an impedance number from the hot side to get that figure though.......
 
If I remember correctly the RESISTOR in series with an INTERNAL connection from say (EQ or filter stage) is around 10 or 30 Ohms (to ensure stability of the drive stage when it feeds cabling and PCB tracks inside the desk so around 47 Ohms or so would be suitable as although it is not really near 'balance' it will likely just work because it would also work UNbalanced and you are not driving LONG cables (hunddreds of feet in a 'hostile environment' and in any case balancing works because the recieve amplifier stage CMMR is what does all the work of noise rejection in this case. Getting obsessive over 'balancing' is a bit ridiculous when you realise the extremely wide tolerances and multiple factors that come into play so you could use your masters degree in electronics and spend a day with your calculator or sopreadsheets and STILL only have an approximate answer which will then be invalid if you change anything.
 
Matt Syson said:
If I remember correctly the RESISTOR in series with an INTERNAL connection from say (EQ or filter stage) is around 10 or 30 Ohms (to ensure stability of the drive stage when it feeds cabling and PCB tracks inside the desk so around 47 Ohms or so would be suitable as although it is not really near 'balance' it will likely just work because it would also work UNbalanced and you are not driving LONG cables (hunddreds of feet in a 'hostile environment' and in any case balancing works because the recieve amplifier stage CMMR is what does all the work of noise rejection in this case. Getting obsessive over 'balancing' is a bit ridiculous when you realise the extremely wide tolerances and multiple factors that come into play so you could use your masters degree in electronics and spend a day with your calculator or sopreadsheets and STILL only have an approximate answer which will then be invalid if you change anything.
Click to expand...

I guess it's a good thing I didn't get a masters degree in electronics, then!
 
i am in the middle of racking a pair of these in line. Just wondering if anyone has the Pin connections required, the schematics are blurry and hard to see.
Any tips from someone who has racked these would be much appreciated especially on the logic switching, not familiar with this. They are complicated little bastards.
Thank you in advance
 

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