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I just got an XLR-mono jack cable from a friend and am trying to understand why such a cable exists and what problems would it solve.

I have those combo XLR/jack inputs on my speaker so I tried plugging a mic into using that cable mic[XLR]->speaker[jack]. The result was a very low mic volume compared to XLR-XLR. Am assuming the reason being the jack input in the combo skips the microphone preamp.

Also, what I've seen so far, the jack inputs are usually line in, so a mic there wouldn't make much sense either.

I'm looking for a use case what problem does a cable like that solve?

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  • I typed up a long answer but the short one is: XLR connectors are not only used for microphones.
    – Todd Wilcox
    Mar 16, 2019 at 0:21
  • Speaker? It's confusing. If it's only a speaker, it's not designed to plug any mic into.
    – Tim
    Mar 16, 2019 at 10:23
  • @Tim Almost certainly a powered speaker with a built in mic preamp.
    – Todd Wilcox
    Mar 16, 2019 at 11:58
  • @ToddWilcox - thanks for the info. I'm not fussed about powered speakers, having had a couple go faulty on gigs - and no chance to use them as passive speakers to get through! So those are virtually a 'combi' amp/speaker, like we use for guitar?
    – Tim
    Mar 16, 2019 at 13:50
  • @Tim Even more: amp/speaker/mixer :) This is the one I'm using but there is plenty of different vendors to choose in this category.
    – TheMeaningfulEngineer
    Mar 17, 2019 at 13:27

3 Answers 3

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The confusion probably comes from the fact that each type of connector/cable is used for two different signal levels.

  • XLR cables (three-conductor cables with XLR connectors on the ends) are used for both microphone level signals and line level signals.
  • 1/4" TS cables (two-conductor cables with two-conductor 1/4" connectors on the ends) are used for instrument level and line level signals.
  • 1/4" TRS cables (three-conductor cables with three-conductor 1/4" connectors on the ends) are pretty much only used for line level signals.

Many audio devices have 1/4" TRS jacks for line level input and output, many have XLR jacks for line level input and out, and many have both. Since it's not always predictable when there will be 1/4" TRS or XLR for line level signals, it's very helpful to keep some XLR (male and female) to 1/4" TRS adapter cables around.

Here's the thing, just because you can plug a cable in, using an adapter or not, does not mean the signal that you're sending on that cable is appropriate for the device you're sending it to.

You normally can't plug a microphone into a 1/4" TRS input, because microphones need mic preamps, and mic preamps pretty much universally have XLR inputs.

What you have is called a Neutrik Combo Connector, which is both an XLR input and a 1/4" TRS input on one connector. But those two inputs are connected to different electronics. The XLR input goes to a mic preamp and then to line-level processing before being amplified up to speaker level. The 1/4" TRS connector bypasses the mic preamp and goes right to the line level processing. Without the mic preamp, the mic signal is too quiet for the speaker. The reason why there is a 1/4" connector that bypasses the mic preamp is for line level signals.

Aside from connecting gear that has different connectors for the same kinds of signal, there's another big use case for XLR to TRS adapters. When you have a stage snake that is all XLR (my personal preference), and you want to connect devices with 1/4" TRS I/O on either end of that snake, then converting to XLR and back makes that easy.

One thing XLR cables can do that 1/4" cables can't is daisy chain, which means you can take two 25' XLR cables and plug them together to make a 50' XLR cable - without any adapters or gender changers. So if you need to connect two devices that are very far from each other using 1/4" TRS connectors, and you have TRS to XLR adapters and a bunch of XLR cables lying around, you can effectively make a very long TRS cable.

There are other use cases, but I hope this has been enough of an explanation.

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  • I have several mics - some Shure, that have a jack plug for connection. They're probably hi-z, and work happily when plugged into jack sockets.(Not trs). Also, I've found speakers with XLR sockets (sometimes the combined Neutrik sort) so aren't surprised if that's what has to be used. Obviously it's not a lot of good plugging a mic in there - whatever's on the end of the lead! Didn't know that daisy chain meant the same as extend -thought it was more for using one source to power several items -as in psu with a few DC plugs emanating from it, in parallel.Balanced leads extend -no power loss.
    – Tim
    Mar 16, 2019 at 9:32
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Typically I have used these cables for plugging a microphone into a guitar amp for club settings where a PA isn't available.

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  • Isn't the guitar output higher than the mic one? So you have to make up for this by pushing the guitar amp much more than normally?
    – TheMeaningfulEngineer
    Mar 15, 2019 at 22:15
  • You are probably using an impedance matching transformer, which is more than just an adapter. And also, a guitar amp is like a mic preamp, especially if the impedance is matched correctly, and the asker is unknowingly bypassing the mic preamp on their speaker without having a guitar preamp instead.
    – Todd Wilcox
    Mar 16, 2019 at 0:19
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Is the XLR male or female? It's not THAT long since the era when microphones had standardised on plug-in XLR cables but many semi-pro PA amplifiers still used 1/4" jacks. Many of us plugged our SM58 mics into a HH MA100 mixer-amp in the 70s and 80s. And, as @pro says, a guitar amp is still better than nothing as an ad hoc PA.

Speaker outputs also ranged from binding posts to 1/4" jacks or XLR-3 (there were so MANY ways to blow up a mic in those days) until we standardised on Speakon. We carried all kinds of weird adapter cables!

Even now, pro gear puts Line signals on XLR-3, plenty of semi-pro gear uses 1/4" jack. Perhaps that cable was feeding a powered monitor in a home studio setup?

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  • It's a female XLR male jack.
    – TheMeaningfulEngineer
    Mar 15, 2019 at 21:58
  • Could well be a mic cable then. Like I said, ALL my mic cables were like that in the 70s and 80s. Later even.
    – Laurence
    Mar 15, 2019 at 21:59
  • Do I read you correctly then when I read what you wrote as "there are mixers that have mic preamps for 1/4" jack inputs"? Because my speaker doesn't have the gain to power this kind of connection. The (1/4" jack) mic is barely heard while the (XLR)mic or (1/4" jack)guitar are to loud and cause a loop instantly.
    – TheMeaningfulEngineer
    Mar 15, 2019 at 22:09
  • There WERE. Not so much now. But some people still use older gear. I remember feeling EVER so professional when I got my first amp with XLR mic inputs! And some people get by with a dynamic mic into a guitar input.
    – Laurence
    Mar 15, 2019 at 22:17
  • +1. I still carry adapters such as this in case I need to use them. Where's the problem? Nowhere!
    – Tim
    Mar 16, 2019 at 9:37

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