You can plug a 1/4" jack into a female XLR socket

[The Paul meister]

I don't know if this is common knowledge, but I just realised you could do this.

I saw it in the Basics and Beyond 2nd edition SOS online book, under the Audio Interface section.

I'm not sure if the sound quality is any different to plugging in an XLR jack. I don't know if this applies to all audio interfaces, but it does on my Focusrite Scarlett 3rd generation 18i20.

Hopefully someone will find this useful.

Cheers, Paul

[Sam Spoons]

They are called 'combo sockets', you are not actually plugging a ¼" jack plug into an XLR socket but into a jack socket which happens to be built into a female XLR.

However I recently discovered that there are combo speakon sockets which accept a jack plug as well as a Speakon plug. I never knew such a thing existed

[Wonks]

No! You can either

1) Plug a TRS or TS jack plug into a combi-socket (which has both jack and XLR connections), but it's very likely that the input will be line (or instrument) level on the jack and mic level on the XLR (though in a very few instances there's a switch to determine the input level) or

2) Plug a lead with a TRS or TS jack plug at one end into an equipment output socket and then plug the other end of the cable that must have a male XLR connector into an XLR socket on an interface or mixing desk (but you are likely to be plugging a line level output into a mic level input which will almost certainly distort horribly).

What you simply can't do is plug a 1/4" jack plug into a standard XLR (only) socket.

You are always plugging an XLR into an XLR, and a jack plug into a jack socket, even if a combi socket looks rather like a standard XLR. It isn't.

[Hugh Robjohns]

I don't know if this is common knowledge, but I just realised you could do this.

You're talking about Combi-XLR sockets which are common on interfaces, portable recorders, and some mixers.

This is a female XLR socket with a separate quarter-inch TRS socket built into its centre. The TRS socket usually accepts line inputs whereas the XLR accepts mic inputs.

I'm not sure if the sound quality is any different to plugging in an XLR jack.

Sound quality — no. But sensitivity and headroom — yes... usually.

[The Paul meister]

Ok, thanks everyone for correcting me. All your replies might be useful to other people, so I’m glad I made the original post.

Cheers Paul

[Hugh Robjohns]

All your replies might be useful to other people, so I’m glad I made the original post.

Absolutely! What's new to you will be new to countless others too. No one is born knowing any of this! That's why we're here...

[Luke W]

My time working in education taught me that just about anything can be plugged into anything if you try hard enough. Even connectors of wildly different shapes can simply be seen as a challenge rather than an indication of a flawed approach.

[Matt Houghton]

One addendum to the above: while the XLR and jack components of combo connectors are physically separate, and should be treated as such, designers can choose to wire them up in parallel, such that the jack (not just the XLR) carries phantom power when it's switched on. I've seen that on more than one preamp, for example. Probably a good idea to be sure of that before you go plugging things other than mics in.

[alexis]

One addendum to the above: while the XLR and jack components of combo connectors are physically separate, and should be treated as such, designers can choose to wire them up in parallel, such that the jack (not just the XLR) carries phantom power when it's switched on. I've seen that on more than one preamp, for example. Probably a good idea to be sure of that before you go plugging things other than mics in.

Thanks for that reminder, Matt!

I have a little tag at the mixer end of my TRS 1/4" male plug that says, "No Phantom Power Please!", and because I know no one will ever read that, I use transformer isolating boxes (incorrect terminology?) between the mixer and my equipment.

Setup takes a little longer because of those boxes, but I am a little more relaxed about things, which is a good thing!

[The Paul meister]

I have my guitars plugged in using an XLR cable. Is this better than a 1/4" jack? I didn't know when I bought the cables that it could take a 1/4".The 2 guitar/bass inputs accept hi Z, mic or line.

I didn't notice anything saying these were Combi sockets when I bought my audio interface, but maybe it's in the manual? If anyone is buying an interface, portable recorder or mixer, I don't know how you would know if they had Combi sockets. Maybe do some research, eg if you can find the manual for your product. I didn't know before I bought my interface.

All the 8 inputs on my interface accept either mic or line inputs. I don't know how it differentiates between these, but it must. Is it always that a 1/4" jack is line, and XLR mic? Or could you put in a line level XLR and it would recognise that? Again, this might be in the manual.

You say, Hugh, that the Combi socket accept TRS jacks. So this means balanced? Also, is an XLR input always balanced? Obviously a guitar is a mono input so this must be unbalanced.

Any views on this most welcome.

Cheers, Paul

[Wonks]

It's a combi socket if its got a hole in the middle of it. And if it's got one there won't be a separate jack socket for a guitar input.

Your issue with using an XLR for your guitar cable, is that the Hi-Z option for directly connecting a passive electric guitar won't work on the XLR connection (unless you have a physical line/mic level switch for the input).

If you want a Hi-Z input, you'll almost certainly need to use a TS jack plug and the jack input. Otherwise you'll only get mic level operation (so the guitar signal will be very hot in comparison) and the guitar will see the mic input impedance of probably somewhere around 1.2k to 2.4k ohms. You'll loose an awful lot of treble as a result, like turning your tone control fully down.

[Hugh Robjohns]

My time working in education taught me that just about anything can be plugged into anything if you try hard enough. Even connectors of wildly different shapes can simply be seen as a challenge rather than an indication of a flawed approach.

Sadly very true!

Did you know a mains cable fitted with a 'cloverleaf' connector for a laptop PSU...



...will fit into an XLR3m audio output socket, given only 'moderate' encouragement?



Nope, neither did I.

But PW saw the smoke come out of his subwoofer after asking a 'helpful' person to connect up the subwoofer's mains using "cables in the bag..."

[Luke W]

Did you know a mains cable fitted with a 'cloverleaf' connector will fit into an XLRm audio output socket, given only 'moderate' encouragement?

I do now!

But PW saw the smoke come out of his subwoofer after asking a 'helpful' person to connect up the subwoofer's mains using "cables in the bag..."

[Matt Houghton]

That's almost worth recreating and filming for SOS, just for the YT and TikTok views that would follow

[Matt Houghton]

It's a combi socket if its got a hole in the middle of it. And if it's got one there won't be a separate jack socket for a guitar input.

Depends on the device. Some gear has combos for mic (XLR) and line (jack) on the rear, and dedicated high-impedance instrument inputs on the front. Eg I think some of the SSL interfaces do that.

OP: generally, your guitar won't want to be patched directly into an XLR. You might get a signal, but it will likely be at the wrong level (so noisy and maybe distorted) and your guitar's pickups won't see the right impedance to allow them to do their best. Typically XLR sockets are used either for mic or line-level signals. On pro gear, mics will almost always connect to XLRs. Line-level signals might go into XLRs or jacks. Guitars will pretty much always go into jacks. Though if your interface doesn't have an instrument input, you could get a separate DI box that will offer a jack input and present the right impedance to your guitar's pickups, and then send a mic level signal out on XLR — you'd connect the DI box to your interface's XLR mic input using an XLR<>XLR cable.

[Hugh Robjohns]

I have my guitars plugged in using an XLR cable. Is this better than a 1/4" jack?

No, almost certainly not. The XLR input is expecting mic level and presents an impedance of around 1.5k to 2.5k ohms. A guitar needs to see more than 500k and most hi-Z inputs present 1 Meg Ohms.

The 2 guitar/bass inputs accept hi Z, mic or line.

I suspect it would only offer line or Hi-Z options on the TRS jack input socket within the combi-XLR, so I would advise swapping to a standard guitar lead and plugging into the TRS socket and selecting Hi-z (or using the sockets that present hi-Z).

Is it always that a 1/4" jack is line, and XLR mic?

As a rule, yes, although there will always be exceptions. And the TRS can be line or instrument, very often.

You say, Hugh, that the Combi socket accept TRS jacks. So this means balanced?

All combi-XLRs accept TRS plugs... whether they are wired up internally for balanced or not depends on the product, but most will accept balanced line level signals on TRS plugs, or unbalanced line or instrument level signals on TS plugs (either automatically, or with some user-selected switching).

Also, is an XLR input always balanced?

Yes... but, again, with some (very rare) exceptions. (For example, the XLR input on a BSS AR-133 DI box is unbalanced!)

[The Paul meister]

That’s great Hugh,

Thanks for taking the time to answer everything

[The Elf]

Is it always that a 1/4" jack is line, and XLR mic?

As a rule, yes, although there will always be exceptions. And the TRS can be line or instrument, very often.

From a quick scout around my studio I'd say I have as many, posibly more, XLR line inputs than mic inputs.

[ef37a]

My time working in education taught me that just about anything can be plugged into anything if you try hard enough. Even connectors of wildly different shapes can simply be seen as a challenge rather than an indication of a flawed approach.

I would like to add to that to say that "newbs" to this audio game are often very wary of experimentally connecting differing pieces of kit together? This is rarely a serious problem (assuming they don't break the plugs!) and most audio sources can feed most inputs with impunity. The result might distort horribly or be very noisy, hiss or/and hum or be too low a level to be useful but you almost never cause any electrical damage.

Two BIG caveats! Never connect the output of a power amplifier to anything but a properly rated speaker or dummy load. Never allow phantom power to go to anything other than mics and other equipment designed to handle it.

The point about a guitar into a mic XLR input is interesting? When an input impedance gets very low the "system" becomes a current source and the response gets seriously modified. An example is ceramic PU cartridges fed to a 47K (instead of 1M+)phono input where the RIAA correction sorts the response out to a fair degree.

Be interesting if someone who has the kit ran a test?

[Wonks]

The point about a guitar into a mic XLR input is interesting? When an input impedance gets very low the "system" becomes a current source and the response gets seriously modified. An example is ceramic PU cartridges fed to a 47K (instead of 1M+)phono input where the RIAA correction sorts the response out to a fair degree.

Be interesting if someone who has the kit ran a test?

If you mean the effect on the guitar tone, I mentioned the variable input impedance switch on my Two Rock amp about half way down this thread.

https://www.soundonsound.com/forum/view ... hp?t=94210

The lowest DC impedance setting I measured was 7.5k (higher than a standard mic preamp impedance but still very low for a passive guitar) and it was very much like turning the guitar's tone control all the way down. All bass and very low mids, nothing noticeable in the higher frequencies.

[James Perrett]

All bass and very low mids, nothing noticeable in the higher frequencies.

Which is close to what you want for an RIAA ceramic cartridge preamp but not for guitar - unless you are into super smooth jazz.

[The Paul meister]

I just did an A to B comparison between the XLR and 1/4" jacks with my guitar. There is a noticeable difference - as everyone has said the treble is a lot better.