Whaddaya mean by combo?

A turnaround, or a chassis mount connector?

XLR to TRS adapters are wired as follows:

XLR Pin 1 = TRS Shield
XLR Pin 2 = TRS Tip
XLR Pin 3 - TRS Ring

If adapter, that's all you gotta do.

If you're talking a chassis mount combo connector, then you gotta jump the proper pins to the proper solder points listed above.

I'm assuming you mean that you want to replace an XLR socket with a combo XLR/TRS socket. These are normally used to save panel space on preamps that have both mic and line inputs.

The mic input on the XLR is usually wired separately so that (1) the line input can be padded before feeding the XLR circuitry, and (2) phantom power can be applied to the XLR pins 2 and 3 and not to the tip and ring of the TRS. If this is also your application, then I would advise for safety's sake not to jumper the TRS pins to the XLR pins.

If there's no PP involved and you want the sensitivity of the two inputs to be the same , then wire TRS tip to XLR pin 2 and TRS ring to XLR pin 3 as Bent advised. The TRS sleeve and the XLR pin 1 are often hardwired together in the combo connector as ground.

If your existing XLR socket has wired connections, you should be able to replace it with a wired combo socket. You will encounter much greater difficulty if the XLR is PCB mounted, as the pinning is different on the combo connectors.

Yes. I'm looking at replacing a chassis mounted XLR socket with an XLR/TRS combo. The unit has switchable Mic and Line Level input but only through the one XLR socket (actually 2 sockets for stereo) I figure if the XLR is replaced with a combo socket, it will be a bit more versatile and accept more input options.

The other option is of course a short breakout cable with a TRS socket on the end.

I could however be completely off the mark.

Boswell wrote: If this is also your application, then I would advise for safety's sake not to jumper the TRS pins to the XLR pins.

As someone who has grabbed the live end of a TRS plug with 48VDC running down the line, I would have to agree.

Let's just say, get a taste of that and there will be a stain on the floor that is difficult to explain.

Cucco:
A big boy did it and ran away!

Yes, correct...

If the pre supplies phantom, don't jump the pins!

8)

Unless you've got good machining skills and room in the chasis to work with it, I'd say: go with the breakout connectors and save yourself a lot of agg.

OTOH, if you're into rolling up your sleeves and popping the top; go for it, but be careful. You'll definitely want to reinforce the socket somehow, somewhere, because it'll get a lot of wear and tear; normal abuse even when just plugging and un-plugging stuff. Using the solder traces alone is always very very wrong. (And I"ve seen it far too many times in cheapo gear that is built cheaply....esp certain keyboard manufacturers!! Grrrrr.....)

Try to find an additional way to reinforce the mounting rather than just the PCB & solder joints; you'll be glad you did.

I've never been shocked by 48V Phantom power, but I believe it exists, and I know what happens when it's missing: Nothing! :twisted:

Thanx for all the replies and info

I think for sanity sake, I'm going to use break out cables and save myself all the grief if I scre it up.

Regards
John