Problem using PC headset mics with a Yamaha audio mixer...

And you know I wanna say I thought that this mixer did take mics in the 1/4" openings on the first two channels but I couldn’t find it in the book for the life of me or remember for certain. I also don’t have an xlr mic to 1/4 male adapter to plug my regular dynamic mic in to try it. I’ll keep looking. It would be alot nicer to use the 1/4’s. Thanks for the heads up bout the black bands.

From the Yamaha website!:
" The XLR-equipped stereo channels can accept mono microphone input either via the XLR or phone jack connectors. "

I knew it. Thanks for the reminder to check on that!. You just saved me a chunk of money and work buddy :slight_smile:

That’s good. I forgot about those screw terminal strips. Maybe the worst problem with those is the capacitor. The leads may not be long enough to reach the screws. If you have the option of getting a capacitor whose leads stick out the ends rather than both on one end, it may fit better. They come both ways.

The 10K resistor can be jammed right across the leads going to the mixer.

He used a 1800 ohm resistor (brown, gray, red) rather than a 2200 (red, red, red) and both would probably work. They’re very close.

http://samengstrom.com/24614782/en/read/4_Band_Resistor_Color_Codes
The first three bands are the value and the fourth is the accuracy. Red, red, red, is 2, 2, with two zeros. 2200. The fourth should always be gold. I think that’s 5%.

The metal box should be connected to the lead that goes to the shield/sleeves or grounds. That’s the bottom wire in that pencil sketch. The metal box then becomes part of the wire shields on both ends and forms a protective bubble around your circuit.

Whatever happens mechanically at the XLR end, the signal has to go to pin 2 and the shields have to go to both pin 1 and pin 3. It’s possible to mess with this, but that’s the standard. Pin 2 always gets the main show and Pin 1 always gets ground or shield. Pin 3’s job changes depending on the type of connection. In your case, it becomes part of the shield system.

Koz

Here’s another resistor color code diagram with fewer fancy animations.
http://www.csgnetwork.com/resistcolcalc.html
Koz

I’m just catching up with the messages. If you use a mono plug into the mixer, just tip and sleeve, then my pencil sketch is the wiring. The long sleeve connection will take care of the extra ring contact found inside the mixer (the equivalent of pin 3 on the xlr).

Koz

Just catching up on these posts too. Busy weekend. Made it to the supply house and surplus store but haven’t had a chance to put anything together yet.

<<<That’s good. I forgot about those screw terminal strips. Maybe the worst problem with those is the capacitor. The leads may not be long enough to reach the screws. If you have the option of getting a capacitor whose leads stick out the ends rather than both on one end, it may fit better. They come both ways.>>>

Found capcitors with “end leads” so hopefully that works.

<<<The 10K resistor can be jammed right across the leads going to the mixer.>>>

Wanna make sure I understand you. Where exactly do you mean if I’m using this layout with a terminal strip?

<<<He used a 1800 ohm resistor (brown, gray, red) rather than a 2200 (red, red, red) and both would probably work.>>>

Got 2.2’s. Good to know though.

<<<Here’s another resistor color code diagram with fewer fancy animations.>>>

Great diagram. Very helpful indeed.

<<<If you use a mono plug into the mixer, just tip and sleeve, then my pencil sketch is the wiring.>>>

Mono plug is the plan so I’lll follow the sketch. Thanks!

So okay. I just got a crazy idea. Not sure if this is outside of your area of expertise but any advice you have on this would definitely be helpful.

What if instead of using a 9v battery with a resistor, I did the following:

I have an extra computer power supply collecting dust. It’s about the cheapest one you can buy but it has several “+5v” pin connectors on it. I’ve already connected the “grey and green” connectors on the 24-pin connector to make it a stand alone unit that I can use without it actually being connected to a computer.

I also have harnesses to connect to the power supply connectors to create leads. That means… I can make several 5v connections off of the power supply and wouldn’t need to use batteries… OR the 2.2k resistors (to bring the 9 volts down to 5)?

Am I even on the right planet? I feel like I’m probably missing something but it would be cool to not have to use batteries. I would still use the capacitors and the 10K resistors of course.

I think I can use the three “red” +5v pins on the big 24-pin connector OR the three heads on the 4-pin cable in a chain and get the same effect. Yes?

It’s a basic ATX12V power supply.
http://en.m.wikipedia.org/wiki/Power_supply_unit_(computer)

This one specifically:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817170014

Also on the 1800 ohm resistor: He used a 1/2 watt. I think Steve suggested using a 1/4 watt or 1/8 or 1/16. Not a big deal right?

Thanks again bro. Just wanna make sure I do this right :slight_smile:

In reverse order:

The physical size of the resistor doesn’t matter in this case. That only matters when there is physical heat – the parts get hot to the touch and you have to manage the heat. These parts will never see anything like that in normal operation.

Which brings us to the batteries. If you unplug the microphones after each use, the batteries are expected to last almost the shelf life, certainly a year or more. The unit in the pictures has never had its AA batteries changed. I think it’s two years old.

And that brings us to the power supply.

Qualified yes. It’s a delightful idea to replace the batteries, but you should keep in mind the signals from the microphones are stunningly small. I use the phrases Tiny, Delicate and Wispy to describe them. Putting a wall-type power supply in connects the microphones to the home power system with the clicks and pops every time the refrigerator or air conditioner kicks in. And now we’re talking real power, force, horsepower–literally, the power of horses, and heat. Not Wispy.

However. You should try it. You could luck out and everything stays quiet and not have to buy batteries ever again.

The supply system inside the sound card runs from the computer 5 volts and it’s happy there. I made two units, one where I actually made 5 volts and the other where I used four AA batteries for six volts. I suspect 9v is the upper end where I would be comfortable running the microphones. Many commercial electret microphones run just fine on one 3v watch battery. Like this one…

http://www.radioshack.com/product/index.jsp?productId=2102927

OR the 2.2k resistors (to bring the 9 volts down to 5)?

The job of the resistor is to bring the 5 volts down to about 1.5. Anything you do over that is pushing it.

The volume of the sounds goes up slightly with the voltage, but don’t fall in love with that.

Sooner or later, you’re going to run into the breakdown voltage of the little transistor inside the microphone and destroy it. The voltage on both sides of the 2200 resistor goes up. The resistor doesn’t just soak up the difference. It shares.

Koz

I dug in the bags of parts and came up with a “raw” electret microphone element. This one…

http://www.radioshack.com/product/index.jsp?productId=2062216

The specifications on the back are for a maximum supply voltage of 10 volts with a design center of around 4.5v to 5v. The actual voltage of a nine volt battery is 9.65 volts.

Watch your step. Koz

<<<The 10K resistor can be jammed right across the leads going to the mixer.>>>
Wanna make sure I understand you. Where exactly do you mean if I’m using this layout with a terminal strip?

There is a wire going to the tip of the 1/4" plug and a shield wire going to the sleeve of the same plug. This is the plug on the right of the diagram that’s going into the mixer.

Those two wires have to go into the terminal strip. Jam one resistor lead and the tip wire into a terminal. Jam the shield wire and the other side of the resistor into another. You’re allowed to put two or more things into each terminal – as many as fit.

Koz

Thanks for clearing up the wattage and terminal strip questionsis. Makes sense.

<<<The job of the (2.2K) resistor is to bring the 5 volts down to about 1.5. Anything you do over that is pushing it.>>>

&

<<<The voltage on both sides of the 2200 resistor goes up. The resistor doesn’t just soak up the difference. It shares.>>>

Just a little confused here still. I thought we wanted to send approximately 5 volts to the microphone… So why do we want to get to 1.5 volts? I thought the purpose of the 2.2k resistor was to bring the 9 volts down to 5 volts so you could send that original 9 volt signal to the microphone at approximately 5 volts.

What I was wondering is if I would even need the 2.2K resistor between the power source and the microphone. If the original voltage is a steady 5v… then no resistor is needed between the 5v power supply pin and the mic right?

It’s the 10K resistor that would bring the 5v from the power supply pin down to about 1.5v right?

Can’t thank you enough for your patience and help! I swear I’m getting about 99% of it lol. I’ll be sure to contribute as many pics and tips as possible to the forum once I’m done.

More bad graphics from Photoshop®.

This is what’s going on inside your microphone. The sound waves wiggle the plates of your condenser which generates a very weak signal. The transistor makes the signal hardier and more robust (but not any louder) so it will go down the cable to your mixer. All condenser microphones have a booster somewhere. In the early days, it was actually a vacuum tube. Those wacky looking things standing up in front of Adolph Hitler were condenser microphones.

The transistor pulls or releases the Ring connection in response to your voice. It’s working against the 2200 resistor. The resistor is part of the microphone, it’s not optional; it’s fairly critical and it’s built into every soundcard. If you put battery directly on that connection you will probably fry the transistor.

Koz
hitlermicrophone540.jpg
ElectretMicrophone.jpg

All the 10,000 resistor does is “settle” the voltages and currents in the microphone circuit before you plug the mixer in. If you don’t do that, plugging in the microphone will put a brief hit of battery voltage on the audio line – and it will go straight through the DC blocking capacitor into the mixer.

When you plug the microphone in, there is still a brief hit of 9 volts on the sound line, but it quickly leaks away harmlessly into the sleeve/shield through the 10,000 resistor. By the time you plug the mixer in, there is clean audio on that wire and nothing else.

Koz

Awesome! The drawing answers my questions. I’ll take a crack at it.

By the way, I had an even older (fried) power supply collecting LOTS of dust. I took everything out of it and it seems like the perfect little metal box for mounting three circuits in. :slight_smile: Its already got a couple of small holes, some ventilation, a spot to screw the ground wires, a tight lid and it’s the same size as the power supply so it should work great. I’m guessing that’s exactly what the box is designed for, basically housing one really BIG circuit.

I’ll probably build one circuit first and test it to see if I can hook it to house power without wierd fluctuations and pops like you cautioned me about. Crossing fingers.

I’ll be sure to contribute as many pics and tips as possible to the forum once I’m done.

That would be good. We get asked this all the time and there was never a beginning to end story about how to do it.
Koz

Ok, this morning I built the circuit, and it works, but is very noisy (background hiss).

I’m using a 7805 for my 5V supply, with a 9V battery driving it. I think its likely to be my issue.

I was using the http://www.epanorama.net/circuits/microphone_powering.html under Multimedia microphones to normal microphone input
I did not include the 10k resistor between the signal and the ground, but I don’t think its the cause.

So, question, is a 7805 a bad choice? Looking back at the application notes I think I used a 22uF capacitor on the input side rather than a .22uF, and I skipped the output 0.1uF capacitor. Which the application notes for “stability and transient response”. Eh.

The cap bridging the audio signal path is a electrolytic similar to Radio Shack part VHT10M50. Any comments?

If I can fix the hiss I’ll post the part list.

Ok, checked, used the correct value (0.22uF) for the input side capacitor, tried temporarily adding the recommended 0.1uF cap to the output side with no discernible result. Signal is clear and fairly strong, but has a strong computer style hiss.

Enclosure is a plastic box…

I’m about to take a whack at this. Been sitting on the parts for a while and finally have some time. Should have some updates soon.

Quick question about 1/8 in leads. Instead of ruining the cord on my headset/mic, I’m using a 1ft. long 1/8 female plug with bare leads to wire into my plastic circuit strip as I discussed earlier. It’s a stereo cable which means there are 3 wires: red, white and green. I know all I need for the circuit is Tip and Sleeve. I assume green is ground so that’s my Sleeve. Is that right? In this video (@4:36), the mic he is using only has two leads (the white wire on the left)

http://m.youtube.com/#/watch?v=JPxqluZkS2o

Which two wires should I use out of the green, red and white leads? Or should I twist red and white together? Thanks.

Ok gave it a try. I ended up twisting the red and white together and treating them as Tip. I put the extra 10k resistor and everything else where it was suppossed to go. No sound at first but I wiggled the connections and got a loud POP and peak lights on the mixer. I assume something wasn’t connected tightly somewhere and whatever I wiggled fixed it. After that, I got sound!

Two problems:

  1. I get sound when I tap on the mic gently, but when I tap harder I get big crackles and pops. Same when I blow into the mic. Gently is fine but louder same as tapping.

  2. I have to have the level and the gain on the channel CRANKED to even get any of that at all. To the point where I can hear the hiss of the floor noise.

I also didn’t ground it to the hollowed out computer power supply box I’m using yet.

So it’s not even close to where I need it to be to record with it, but I’m happy to have sound. Any ideas about what I’m doing wrong?
Thanks!