Getting an XLR mic to feed into a computer mic input

[bowesj]

Hi, I am trying to do something simple and it is not working. Maybe someone can figure out what I am missing here.

I have a low impedance Shure mike. I am feeding it out through a transformer to 1/4 inch phono. I have tested it with a guitar amp and it is working fine. My computer has a 1/8th inch stereo mic input plug. I just bought a 1/8th inch stereo male to 1/4 inch stereo female adapter. So I have a 1/4 inch stereo extension chord which has a male on one end. I plugged this into the 1/4 inch stereo female end of the adapter that I just mentioned. I plug the adapter into the computer of course (I made sure it was plugged in full distance). I then cut the female end of the 1/4 inch stereo extension chord off and I took the plastic off the wires. So I have an outer braided part I figure is the ground and I twisted that up nice and clean. I then have a red wire and a white wire which I exposed and twisted them up nice and neat (I assume these are the left and right of the stereo). So I am testing it before I do any soldering. I am touching the outer braided wire to the tube part of the 1/4 inch mono phono from the mic transformer and touching both the white and red to the tip of the 1/4 inch Mono phono from the mike. This connection makes the least amount of hum but it is not producing any sound. I plug a regular computer mike in and I do get sound (in other words the mic input of the computer is working). The adapter is new so I have to assume it is working fine. The stereo extension I plugged into the adapter I am 99% sure is working fine. When my connection I explained here did not work I tried a few variation and most of them give a hum. So I think I have exhausted everything I know here.

Thanks,
John

[Richard]

Checking continuity is the first thing I would do. To the best of my knowledge your setup should work. Have you tried using the 1/8-1/4 adapter with headphones to verify it works? There's not much to go wrong but sometimes things do that. It's possible that the mic input on the computer is designed for a different type of input or that splitting the signal is pulling the level too low. Did any of the other variations give you sound at all? Your best bet is to get a usb microphone interface, the sound quality will probably be much better than the mic input on your computer and you can get a basic one for $50-$100.

[The Dude]

I'll confess from the get go that I only skim read the OP before confusion set in, so excuse me if what follows was covered or tried.
Most PC mic inputs are not stereo inputs, but a mono 1/8", so you need a hot and ground...... that's it. For a balanced to unbalanced input from XLR, you would tie pins 1&3 of the XLR together to an 1/8" mono connector. If you are using a transformer, then the unbalanced output would go directly to a mono 1/8" plug- no stereo plug involved.

[Steve A.]

This link explains how the mic input on a sound card works and includes a schematic for a mike preamp.

Sound card microphone

Steve Ahola

[bowesj]

Thanks guys for replying so fast. I just tried Richard's headset idea and the adapter works.

The mic input to the computer is a stereo (probably because it is a multi media machine). To confirm this: I do have a cheapo computer mic with a 1/8th inch stereo phono plug and it works fine. I know a mono 1/8th going into the notebook computer will not work because I tried this with an adapter out of my guitar and it would not work yet I did the same with my desktop and it took the mono 1/8th inch plug and works. So the only explanation for a mono 1/8th working on the desktop but not working on the notebook computer is they decided to put a stereo 1/8 inch plug into the notebook computer because it was a multimedia machine.

As an aside I tried feeding the mic through an old teac model 2 mixing board using the low to high impedance transformer into the board and using two RCA outputs to the computer stereo input (the wire merges the two RCA to a 1/8th inch stereo phone) and this works. I was hoping I didn't have to use the board however. So maybe the mic alone just does not have enough power although it seems strange that a simple cheap computer mike would work.

[bowesj]

I just read Steve's schematic. The first thing I read is an electret microphone works best. I have one. It takes a 4.5 volt battery. Unfortunately I don't have one kicking around.

I read Steve A's text again. If I had more time I would try wiring up the XLR connector directly to a 1/8th inch stereo mic male plug the way it shows. At the moment I am using the computer to record demo recordings for a jazz jamming group project I am involved in and practicing my instrument gets priority at the moment. Using the mixing board as a fast work around may have some advantages in that I may find a use for more mics.

[jmaf]

The mic input to the computer is a stereo (probably because it is a multi media machine).

Read Steve A's text : the ring is +5 VDC bias in several popular sound cards, not stereo.

[bowesj]

Read Steve A's text : the ring is +5 VDC bias in several popular sound cards, not stereo.

I don't know enough about electronics to understand the explanation but it never did made sense to me to have a stereo plug on that mic since how can a simple mic be stereo anyway?

[jmaf]

I don't know enough about electronics to understand the explanation but it never did made sense to me to have a stereo plug on that mic since how can a simple mic be stereo anyway?

There are stereo mics but they're composite, like those portable Zoom recorders they have a cap pointed into each direction inside the enclosure to capture some spatial sounds along with the directional waves.

[bowesj]

There are stereo mics but they're composite, like those portable Zoom recorders they have a cap pointed into each direction inside the enclosure to capture some spatial sounds along with the directional waves.

Yes, like this zoom H4 recorder my friend was recommending. I was thinking I may as well use my Bayer ribbon mic which is really good rather than spend the money on his recommended idea. It turned out to be more complex than I thought :-)
https://en.wikipedia.org/wiki/Zoom_H4_Handy_Recorder

What is interesting is when I send a single mic in through my teac model 2 mixing board and assign that mic to two output channels on the mixing board then I pan the input with the mixer's pan control it does pan across the computer speakers. There are two speakers in this notebook computer (again it is a multi media computer). So that stereo mic input does send a signal to different speakers within the computer. So does that not mean it is in fact a stereo mic input????? I don't know the program audacity very well but I seem to remember it can record in stereo so maybe I should try recording tomorrow with this setup and see what happens (if I had time).

[The Dude]

It's not that complex. 2 wires of the XLR from the mic are the balanced signal. 1 is a shield.
XLR Pin 1 is the shield
XLR Pin 2 is positive
XLR Pin 3 is negative/neutral.

Step 1) Connect pin 3 and pin 1 together. Wire them to the sleeve of an 1/8" jack.
Step 2) Connect pin 2 to the tip of the 1/8" jack.
Step 3) Talk into mic.

Irrelevant if you hardwire, make a cable, use adapters, whatever. Just make sure the connections are made as above. If you have a stereo 1/8" plug, ignore the ring connection. It is for phantom power (unless you have a mic that requires 5V phantom power).

[bowesj]

Step 3) Talk into mic.

lol, you are right :-) I should talk because I sure can't sing...lol. Maybe I will make a 2nd trip out to Sayal Electronics to get the parts and try this. Thanks!

[Richard]

If panning your mixer makes the sound move then you have a stereo input. I suggest that the mic just doesn't want to drive the input, as you concluded. Using the mixing board is a good idea, it almost certainly has a better preamp than your computer, plus additional inputs. More mics are better anyway.

[bowesj]

If panning your mixer makes the sound move then you have a stereo input. I suggest that the mic just doesn't want to drive the input, as you concluded. Using the mixing board is a good idea, it almost certainly has a better preamp than your computer, plus additional inputs. More mics are better anyway.

Thanks Richard. I guess a mike which is designed specifically for a computer has more output where as a mike designed for mixing boards and amps has less output. I forgot to mention my teac model 2 mixers are at least 35 years old, not used in a very very long time and I was testing all the controls including the pan when I noticed the sound was panning between the two computer speakers. As I said I am doing demo recordings so I hauled these old clunkers out of the closet. If anyone is interested in the background as to why here is some info. It may be of greater interest if you live near Toronto Canada.

16 Now - Rusty Relaxed Social Jazz Jams and/or Jazz Karaoke Jams | artists, musicians | City of Toronto | Kijiji

I have two model 2 boards. One I am using to feed the sound from the instruments (and "Band In A Box" maybe) to at least 2 amps (one for us players an one for the audience and maybe other amps if someone can not hear properly like a drummer). The other model two will be used for the recording into my old notebook computer. I may use a mike to capture what the audience hears or I was thinking I could take a direct tap off the PA functioning model 2.

[Richard]

You should check how a guitar or bass sounds plugged directly into the mixer, I've only tried it a little and got mixed results. Generally a guitar wants to see a different impedance than a microphone or keyboard, I don't quite understand what's happening but you might get a very different sound than plugging into an amp.

I like the instrument karaoke idea, I can't sing but it would be good to get out of the house.