PM1000 Cinemag Output transformer/summing question?

Hey everyone.
So I finally started testing my pm1000 modules last night and I got power and signal through, I just have a question about how to terminate the output transformer. I'm using a Cinemag CMOB-2S. I'm using test circuit 3 to terminate the output from this http://cinemag.biz/output/CMOB-2.pdf
So since I'm so new to reading schematics, does this mean I should attach a 600ohm resistor between pins 2&3 on the output XLR?

Also since I have a 32 channel board/w the power supplies I've been throwing around the idea of racking 16 modules in one box. This will be after I recap, change/add freq points and add output transformers to every channel. HOWEVER, My question is how hard would it be to make this into a summing mixer? would it just consist of tapping off the - of C37 to some sort of summing circuit then to a pair of output transformers?

Yes on the resistor, it will make the transformer work a little better with some current flowing thru the wires,

There is always a little pri current for exiciting the core, but in audio, sometimes the sec looks into a tube grid, which has an ultra high input resistance, so no current flows.
Putting the 620 on there will give the transformer something to do.

What effect on the transformer would it have if I raised or lowered that resistor value between pin 2&3?

Also would it be possible to use a Carnhill vtb-1148 for the output transformer? I was reading here http://www.technicalaudio.com/reading/neve_xfmrs/neve_edo7113.html and from what I gather the LO 1366 (which is the equivalent of the VTB-1148) has the same 1:1 ratio that the original GA80080 transformer has. Just wanted to double check to make sure that I'm figuring that right?
Thanks for the help

This may be a dumb question, but what are the purpose of the bypass caps that people solder on the underside of the PCB of the PM1000?

Bump on the bypass cap question

CJ said:

Yes on the resistor, it will make the transformer work a little better with some current flowing thru the wires,

There is always a little pri current for exiciting the core, but in audio, sometimes the sec looks into a tube grid, which has an ultra high input resistance, so no current flows.
Putting the 620 on there will give the transformer something to do.

Click to expand...

I would respectfully disagree with the above opinion. The bifilar output transformers you have selected require no terminating load resistor to prevent overshoot or ringing. In over 20 years of designing Jensen transformers, I never discovered any reason why any transformer would work "better" with some current flowing thru the wires.  There are some transformers that require either a load resistor or an RC network on their secondary to properly damp their transient/frequency response.  Bifilar transformers are used as output transformers precisely because their frequency response and transient response is essentially immune to changes in loading.  They work well into short cables, long cables, unloaded or 600 Ohm loaded.  They don't care.  Adding a 620 Ohm load resistor will only result in a heavier load on the output line driver amp in front of the transformer, which will increase THD.  If the transformer is capacitively coupled to the line driver, it will also result in more LF rolloff.  If output line driver amp has low enough offset, it is best to DC couple the connection to the OT.  This prevents a subsonic resonance peak that occurs with the series capacitor and the shunt primary inductance. 

To sum up, I vote "no" on the built-in load resistor on every output fed by a transformer.

Steve Hogan
(former VP Engineering Jensen Transformers)

So here is my next question. I have 2 modules recapped, changed the EQ points, and added the bypass caps to. I'm thinking about using the Carnhill VTB-1148 of the output transformer. I haven't wired up a output transformer in quiet awhile and I'm wondering how to terminate it. Here is a picture of the windings. check me on this wiring.

For the Carnhill VTB1148: http://www.audiomaintenance.com/downloads/carnhill_design_guide.pdf
output at C37 to pin 1 (on xfr)
Ground goes to pin 2  (on xfr)
XLR pin 2 goes to pin 5 (on xfr)
XLR pin 3 goes to pin 6 (on xfr)
XLR pin 1 goes to ground

Is this right? What do I have to do with the other pins that aren't used? When I'm done with this it should be a 8 channel PM1k in a 4u rack case with and external power supply. I'm going to flip the cards vertical to fit them all.  Thanks for all the help.
Brad

For wiring the Carnhill VTB1148 as a balanced direct output: http://www.audiomaintenance.com/downloads/carnhill_design_guide.pdf
output at C37 to pin 1 (on xfr)
Ground goes to pin 2  (on xfr)
XLR pin 2 goes to pin 5 (on xfr)
XLR pin 3 goes to pin 6 (on xfr)
XLR pin 1 goes to ground

Can anybody confirm this Carnhill wiring is correct?