Need help soldering 2 XLRf connectors to one 3.5mm TRS

[JamesT]

Hi all,

I am new here.

The only thing I have soldered in the past are straight XLR and TRS cables.

I need some assistance in making a new cable.

I already have the tools, the connectors, and some spare starquad.

I would like to make a cable that is as follows:

3.5mm TRS to (2) XLRf

I do not want the cable to act as a splitter. I want each XLRf connector to have a different channel.

My intention is to feed a device with ONE stereo input (3.5mmTRS) signals from two different audio sources with XLR outputs

This cable will only be 2-3ft. long.

My thoughts:

The tip of the TRS connector will get pin2HOT from the first XLRf

The ring of the TRS connector will get pin2HOT from the second XLRf

I do not know what to do with the pin3COLDS from either connector (if anything)

Further, do I solder grounds from both XLRf's to the sleeve of the TRS connector?

Help me please.

[John Blankenship]

I do not know what to do with the pin3COLDS from either connector (if anything)

Both Pin-3s are connected to the ground (shield).

Further, do I solder grounds from both XLRf's to the sleeve of the TRS connector?

Yes.

What you are doing with this arrangement is unbalancing the outputs (assuming they were balanced to begin with).

This should work fine if you're feeding the right type of input and observe proper gain staging. There's no way to know that from your description as you didn't give us any information on what device and output connection is feeding what other device and input connection.

Good luck.

[Matthias Richter]

some devices (like Sounddevices 302) doesn´t like pin 3 and 1 shorted when going from bal to unbal. In that case pin 3 should be left open. (see 302 manual page 11)

[Eric Toline]

Using a piece of star quad might cause problems with fitting into the barrel of a 3.5mm trs connector and attaching the XLR's to the unjacketed ends. You might want to consider using two lengths of a thinner RCA connector cable to fit into the 3.5mm housing. At the xlr ends split the shield into two twisted pigtails, tin them & connect one tail to pin 1 & the other to pin 3. It's a lot easier to do that than trying to solder a tiny wire jumper from pins 1 & 3 to unbalance the connections.

Eric

[Matt Mayer]

Eric has some good suggestions.

The absolute easiest way to do this is to buy a 6' 3.5mm TRS -> 2 RCA adapter cable. Cut it in half, solder on some XLRs using the wiring schemes mentioned. Use the RCA end for another adapter cable and you haven't wasted anything.

This method is also great for BNC adapter cables. No messing around with solderable BNCs or crimping.

[Jay Rose]

I just built a couple of them to feed balanced +4 into a computer tower. As Matt says, easiest and prettiest way is to use a cheap prebuilt cable for the unbalanced mini end.

In my case, I made two separate RCA to XLR female and use a separate cheap RCA/mini for flexibility.

But don't forget the level difference. -10 dBV standard on most unbalanced ins is ~12 dB less than the +4 dBu on most XLR outs. (The other 2 dB get lost in the translation between dBV and dBu.)

Just lowering the unbalanced input level won't protect you from distortion in some input circuits, and kill you if the input has AGC instead of a control. Just lowering the balanced device's output will throw away s/n in most output circuits.

You need a pad.

You can handle this easily with a couple of resistors. In my case I put 1k from pin 2 to pin 3 (jumpered to pin 1), and 3.9k in series from pin 2 to the RCA. Standard 1/8 watt resistors fit nicely in a Neutrik XLR shell/clamp and leave room for shrink tubing over the splices and cable shield.

More and various other details at http://dplay.com/dv/balance/balance.html#cross

By the way, star-quad won't give you any additional noise protection in this kind of adapter, and just makes things more difficult to wire.

[JamesT]

Hey Guys!

This was just what I needed. I will post my notes and my results A.S.A.P.

[JamesT]

Pics

I used the cable and connector from a junk pair of headphones.

I had to refer to another posting on soldering with the annoying litz conductors.

I made a small jumper between pins 1 and 3.

It is not as long as originally planned but it works well for what I need.

However, when I do not have anything plugged into the XLR connectors I hear buzzing. As soon as I plug in a source, they sound great.

My gear:

Zoom H4n (no H4n negativity please, I will upgrade when I can)

Sound Devices 302

Along with borrowed/rented

Sennheiser EW-100s with Tram TR-50s

Rode NTG-3

My goal:

Bypass onboard microphones of Zoom H4n to use the ext. stereo microphone input for 2 more channels.

After making and using this cable, a few downsides have arisen.

A) The 2 tracks I opened up on the H4n cannot be affected individually as they are designed for 1 stereo source. (So unless they can be manipulated before they enter the recorder, their level (relative to each other) is what must be printed)

Monitoring in confidence is limited to listening to all 4 tracks at once.

Note: I confidence monitor from the mixer. mini TRS cable from Zoom HP out to 302 return (I then, of course, use the return position on the rotary HP selector on 302)

The Zoom does not have the functionality to listen to individual tracks on the fly. It does have a virtual mixer that requires the use of multiple buttons, key presses, and an unobstructed view of the unit.

The fact that the sources that utilize my new cable cannot first go through the 302 means that they would have to stay at the level that I set them at.

In conclusion, the Zoom is a fantastic 2 track recorder. Pressing it into a 4 track recorder will lead to worse tracks for me.

This, on account of a lack of flexible monitoring options AND a lack of any mixing capability on the extra sources.

744t here I come!(after some months of penny-pinching and couch-diving, that is)

Is the aforementioned buzzing something that I did wrong in soldering?

[studiomprd]

" the Zoom is a fantastic 2 track recorder. "

they are good for the price, but not, IMHO, as good as the competitive TASCAM's

for example:

http://www.bswusa.com/Portable-Digital-Recorders-Tascam-DR-40-Handheld-4-Track-Recorder-P7747.aspx

http://www.bswusa.com/Portable-Digital-Recorders-Tascam-DR-100-P5697.aspx

Edited May 22, 2012 by studiomprd

[JamesT]

" the Zoom is a fantastic 2 track recorder. "

it is good for the price, but not, IMHO, as good as the competitive TASCAM

If I find myself in the market for another 2 track, I will certainly check out the tascam.

Next purchase for me will be either a 442 or a 744.

[sounddguy]

Using an old headphone cord may give you problems as these are usually not a shielded cable.

And yes, if connecting to Sound Devices, float 3. Just had that discussion about the new pix recorder

with them.