XLR vs. 1/4" Mic Inputs

Bill Sheehan

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You'll probably think that I have too much time on my hands with this question, but here goes...

In general, if I plug my vocal mic (say it's an SM-58) into a typical XLR mic input on a PA head, will that give me a sonic result that is different in any noticeable way from the same mic being plugged instead into an optional 1/4" mic input available on the same PA head?

I have mic cables allowing for both input options, but wasn't sure if either option is thought to be preferable to the other.

Back in the old days (early 70's), my band's mic cables all terminated in 1/4" plugs (rather than XLR), and my recollection is that the mic signals always seemed really hot (when we plugged them into our Bogen PA head)...

Thanks!
 

Wiggy

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Depending on your mixer, the level might be a bit lower when using the 1/4" input, so you may have to turn the volume (or gain) up on that channel. The way the mic sounds however will be the same; just a bit lower level. Try it with the XLR then, leaving controls the same, change to the 1/4" cable and see if there is a difference in level.

- - - About 1/4" cables

Is the 1/4" a TRS (balanced - 2 black rings + tip) or TS (unbalanced - 1 ring + tip)? If a TRS, there may no difference in the level as it is balanced like the XLR.

A 3rd possibility is when the 1/4" cable has a built-in transformer. It's easy to tell as the plug will be bigger and significantly heavier. They are pretty rare nowadays.
 

Gerald_G

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This is an interesting subject. The biggest factor is to understand what "balanced" means. It means that the sending piece of gear (amp, keyboard etc.) sends the sound signal on one wire, and of course there is a ground wire, but on the third wire, it send the sound signal again, but inverted. When the signal reaches the end equipment, that inverted signal in un-inverted, the result being that any interference noise caused by AC hum, RF etc is cancelled out when the now un-inverted signal is re-combined with the original signal. Basically they would work the same unless the cable is passing by a source of interference, in which case the XLR or Tip-Ring-Sleeve 1/4" cable (TRS for short) would have less noisy hum. (Balanced signals can use XLR or TRS cables) See this link for an article that explains it better than I do.

 

Bill Sheehan

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Thank you, Wiggy and Gerald, all of that information is extremely helpful!

(Incidentally, it looks like my 1/4" cables are just of the TS (unbalanced) variety.)

I'll plan to "plug in" soon and tinker around and see if one option seems preferable to the other!
 

Gerald_G

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Thank you, Wiggy and Gerald, all of that information is extremely helpful!

(Incidentally, it looks like my 1/4" cables are just of the TS (unbalanced) variety.)

I'll plan to "plug in" soon and tinker around and see if one option seems preferable to the other!

Most TS cables are intended to run shorter distances. For example guitar to amp on stage, and as such don't pick up as much noise.
Typically then an amp with a balanced output would connect with a balanced cable back to the sound board.
(in the event of the amp not having a balanced output, a DI box would probably be used to send the signal to the soundboard)
 

Bill Sheehan

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Most TS cables are intended to run shorter distances. For example guitar to amp on stage, and as such don't pick up as much noise.
Typically then an amp with a balanced output would connect with a balanced cable back to the sound board.
(in the event of the amp not having a balanced output, a DI box would probably be used to send the signal to the soundboard)
Thanks, Gerald. On reading the article that you linked, as well as your most recent comments, it appears that the main concern would relate to whether or not I was running the cable a long distance; I'd only be looking at 10 feet or so, so hopefully the "noise factor" wouldn't be substantial in that event.
 

Bill Sheehan

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Most TS cables are intended to run shorter distances. For example guitar to amp on stage, and as such don't pick up as much noise.
Typically then an amp with a balanced output would connect with a balanced cable back to the sound board.
(in the event of the amp not having a balanced output, a DI box would probably be used to send the signal to the soundboard)
A quick followup: As it happens, I'm using a Kustom PA50. Each channel has both an XLR input and a 1/4" input. In the Owner's Manual, regarding the 1/4" inputs, it says, "These ¼-inch inputs may be used to connect high-impedance microphones, keyboards, drum
machines and other audio devices." I wasn't sure if that "high-impedance microphone" reference would have any bearing on what we're discussing...
 

Wiggy

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I looked at the PA-50 manual and it shows that the 1/4" input is TS, like a typical guitar cable.

From the manual: "CH 1 and 2 Mic XLR Balanced, Line level 1/4" Un-balanced"

Back to the original question; try it both ways.

I will predict that using the XLR will require less gain on the channel's volume knob (more channel volume for the TS).
Here's why:

System Gain
+70dB Mic to Speaker Output (CH 1 & 2)
+56dB Line to Speaker Output (CH 1 & 2)
+42dB AUX IN to Speaker Output
 
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ksiegel

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On my Kustom PA50, I connect in series using XLR cables, use a TS cable for the monitor out on my mixer into the first of the two PA50 units, and use XLR cables from my mics to the mixer. I use two different MXL condenser mics -one for vocal, one for instrument- when I am solo, and they use the phantom power from the mixer, so XLR it is.

When I perform with a partner, we use Shure SM-58 vocal and SM-59 Instrument mics, all XLR into the mixer.

And yes, I use a mixer, even when solo, so that I can have it next to me, with the PA 8-10 feet away. Plus, I can plug my uke in to the mixer (through a DI box) and balance the sound, with a little darker tone from the piezo pickup.

(The PA50 units are my backups; I use essentially the same setup, but with a JBL Eon One I got a few years back.)

-Kurt​
 

Bill Sheehan

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I looked at the PA-50 manual and it shows that the 1/4" input is TS, like a typical guitar cable.

From the manual: "CH 1 and 2 Mic XLR Balanced, Line level 1/4" Un-balanced"

Back to the original question; try it both ways.

I will predict that using the XLR will require less gain on the channel's volume knob (more channel volume for the TS).
Here's why:

System Gain
+70dB Mic to Speaker Output (CH 1 & 2)
+56dB Line to Speaker Output (CH 1 & 2)
+42dB AUX IN to Speaker Output
Thanks, Wiggy, that makes sense. I'm learning a lot here!
 

Bill Sheehan

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On my Kustom PA50, I connect in series using XLR cables, use a TS cable for the monitor out on my mixer into the first of the two PA50 units, and use XLR cables from my mics to the mixer. I use two different MXL condenser mics -one for vocal, one for instrument- when I am solo, and they use the phantom power from the mixer, so XLR it is.

When I perform with a partner, we use Shure SM-58 vocal and SM-59 Instrument mics, all XLR into the mixer.

And yes, I use a mixer, even when solo, so that I can have it next to me, with the PA 8-10 feet away. Plus, I can plug my uke in to the mixer (through a DI box) and balance the sound, with a little darker tone from the piezo pickup.

(The PA50 units are my backups; I use essentially the same setup, but with a JBL Eon One I got a few years back.)

-Kurt​
Thank you, Kurt! Sounds like you have a very capable setup there!