XLR jack confusion

[Mucker]

Hey all,

I am really enjoying my S3X amplifier. Quite spectacular! I believe I want it to be strictly a headphone amp and have some questions. Most of my headphones are terminated with 4 pin XLR male plugs. I've been using the XLR to TRS adapter but would sure like to plug the phones in without the adapter.

If I were to install an 4 pin female XLR panel mount jack:

1. Is the jack body grounded to the chassis? (Do I need a specific panel mount jack?)
2. Would the wiring from the output transformers to the jack be routed like this?:

1 .... L+ ..... white / green wire
2 .... L- ....... green wire
3 .... R+ ....... white / brown wire
4 .... R- ........ brown wire

I read about needing resistors routed to ground from each jack pin but the more i read, the more confused I became.

Could someone please tell me the exact wiring and resistor placement? I plan to leave the speaker taps and wiring in place but not connected.

Thank you!

Greg

[Paul Birkeland]

You will need to get rid of the 1/4" headphone jack that's installed on the SEX amp in order to do this, since L and R grounds are connected there and common.

If you carefully remove the wiring and the jack, then drill out the hole successfully and install a 4 pin XLR, you would just wire things as you've described, with both wires of each color connected to the same hole (so both white/green wires to L+ pin). 

[Mucker]

Thank you Paul,

I forgot to mention that yes, I was planning on removing the TRS and drilling out the hole for XLR.

I was planning to install a Neutrik NC4FD-L-B-1 (please see attached photo). Does the ground lug need to be wired?

So just wires straight to solder pots and that's all? No resistors needed anywhere? Some of the older posts were throwing me off track.

Appreciate it ....

[Paul Birkeland]

I'm glad you reminded me about the resistors! There are 0 ohm jumpers back at the speaker posts.  You want to remove those and install a resistor between speaker + and the chassis connected terminal, as well as speaker - and the chassis connected terminal.  The value of these resistors isn't all that important, 200 ohm 1/8W or so would do the job. 

[Mucker]

Thanks again Paul!

I attached a photo. So essentially the steps are?:

1. Replace the jack
2. Route all the same colored wires from the speaker taps and OT's to their 4 respective solder pots on the XLR jack
3. Remove the two zero resistors
4. Install 4 resistors as follows (yellow lines in photo)

200 ohm resistor from R+ to H1
200 ohm resistor from R- to H1
200 ohm resistor from L+ to H8
200 ohm resistor from L- to H8

Does that sound correct?

Pardon my illiteracy and thanks for the help ....

Greg

[Paul Birkeland]

Give it a shot!

[Mucker]

Awesome .... thank you!

[Mucker]

I had a chance to hook up my Klipsch RP600M to the S3X. The sound was really good but sightly lacking in warmth because of the lack of full bass (a limitation of the speakers).

If I were using it in a small room for casual listening it would be very livable. However, I have other amps, speakers, subs to handle big full volume needs and therefore don't see a need to use the S3X speaker taps. But nice to have that option if I ever do.

I am now thinking of just taking the TRS jack out and placing the Neutrik there with the OT's wired to it. Then, I will leave the speaker wiring in place but not connected.

A I understand, all I will have to do is solder the 4 resistors from each of the 4 XLR pins to the ground lug on the Neutrik jack which I am assuming will be grounded to the plate once installed. Is that correct?

I have the jack and stepped bit ordered and now waiting (needs a 15/16 inch hole.)

Thank you,

Greg

[Paul Birkeland]

A I understand, all I will have to do is solder the 4 resistors from each of the 4 XLR pins to the ground lug on the Neutrik jack which I am assuming will be grounded to the plate once installed. Is that correct?

Sure, that will work as well.  The earth lug on the XLR jack is usually not all that substantial, so it may take some extra effort to get four resistors connected to it.

[Mucker]

Roger that and thank you Paul!

[Mucker]

I was able to get the Neutrik jack installed tonight. I also modified my DT-1990 Pro and 1770 Pro from 3 pin XLR to 4 pin XLR.

I am super thrilled with the S3X amp with my newly installed XLR jack. The 1990's and HE6se are working great with balanced cables. Will be using Grado RS2e, PS500, Denon AH-D5000, HiFiman Sudara, HE5se ..... all terminated with 4 pin XLR plugs .... good stuffs!

Thanks for the help Paul!

Greg

[Mucker]

Hello PB,

I have a question for you (if you don't mind). I have been looking at adding an XLR jack to my Crack and how to do it concerning grounding. And that led me to how I did the jack on the S3X (shown in the previous posts in this thread).

With the S3X XLR jack, I have a resistor from all 4 pins to the grounding lug on the Neutrik XLR jack which is grounded to the chassis.

Would it be better to route the grounding directly, to say, H1? It would be easy to add an insulated solder turret near the jack, run the resistors from all 4 pins to the turret and then a black wire from the turret to H1. As I understand that will put the signal ground very close to the IEC ground and possibly help with transients???

Or would it be a waste of time? Thank you!

[Paul Birkeland]

The SEX grounding on an XLR jack is not an accurate representation of what would need to be done on a Crack.  You would ground pins 2 and 4 on the XLR jack to the audio ground in the Crack.

[Mucker]

Roger that, thank you. So 2 and 4 to terminal 3  on Crack?

For S3X would it be better to move the grounding from the jack lug and go directly to H1 with a wire? Essentially taking the pin resistors directly to H1?

[Paul Birkeland]

For S3X would it be better to move the grounding from the jack lug and go directly to H1 with a wire? Essentially taking the pin resistors directly to H1?

That is not necessary.  The resistors just form a reference to ground to balance the output and this is far more convenient to do on the grounding lug provided on the jack.