what i am about to ask for may be a little unusual in these forums (i don’t know, this is the first thing i’ve ever posted here, but i am in kind of a tough spot) i need a device that will safely allow me to connect my 3.5mm logitech headset into the XLR of my Behringer Xenyx Q1202 USB mixer. i would strongly prefer not to need to use phantom power but i have seen a user by the name of kozikowski build exactly what i am looking for and if he is out there reading this i am willing to pay you for one of these now, and possibly up to three more later, i do not trust myself behind a soldering iron and my knowledge of circutry is almost non existent. i saw basicially an amplifier connected to an 3.5mm to xlr adaptor. i might be able to come up with the adaptor on my own, but i really need help with the amplifier as i am no good at making home made electronics. if you would please contact me with any way you may be able to help, i would be extremely thankful.
i have seen a user by the name of kozikowski build exactly what i am looking for
Never heard of him.
Casting my mind back. Yes, I did create a power supply to allow you to use a “computer” microphone with a Pro mixer (XLR Input).
You have a couple of the terms mixed up and you’re in really good company. The volume of sound in both XLR and and computer microphones and headsets is roughly the same. Thank goodness you don’t need amplifiers or other exotic electronics.
But you do need a power supply. Computer microphones take 5 volts from inside the computer to work. That’s what goes up the ring connection in a tip, ring, sleeve connector.
Second illustration. Scroll down.
That’s very different from “Phantom Power” which the broadcast and recording people use on their XLR connectors.
Unfortunately, I know of no way to get between them, which is why I and a number of others manufactured our own. I went compulsive and made very stable 6 volts using flashlight batteries (up from 5v). There is little or no changes in the operation of the microphone with the way I did it. Others more adventurous stuck 9v batteries in there and it seemed to work OK, although there was a discussion of what happens to some of the other components when you do that. A 6 or 7 volt rated capacitor will not work in a 9 volt circuit — for long. This is electronic exotica. Don’t worry about it.
Still, I can’t imagine that nobody is manufacturing anything like this. I even found people making the reverse adapter. Start with a good quality XLR (non-phantom) microphone and plug it into a computer. Hosa makes them, or you can do it with Radio Shack parts. Hurry before R/S goes bankrupt.
I’m looking for a long posting we did on that. Someone found a way to make one using exclusively screw together components. No soldering.
Here’s pieces of it.
I gotta stop and read through it. I don’t remember where the construction notes are.
talking with a friend and he seems to want to go the route of regulating the 48 volt phantom down to 5 volts between the pink plug and the 3.5mm to XLR adaptor, however i would like to get as many opinions on this as possible
I did think about that. The problem is you can’t just regulate 48v down by sticking a couple of diodes in there. 48 volts is intentionally a very weak voltage so it doesn’t interfere with the microphone signal. It would be like trying to get the electricity from your hair brush (thousands of volts) to run an electric motor. They don’t match.
So to pursue that line, you would need a phantom power receiver, a DC to DC converter to make the 5 volts and then the rest of the circuitry to actually get it up to the microphone.
Plus debugging. Microphone signals are really tiny and delicate. I live under the neighborhood high tension lines (4000 volts??) and if I make any error at all my sound starts humming and buzzing.
This is where we join the ROI Cycle where the cost of hardware and development time exceeds the cost of an actual XLR microphone. This is probably the major reason you can’t walk to the store and buy one of these.
Did you get far enough in the other dialog to read the construction parts? I know somebody did this with no soldering. He was really determined to get one working.
Son of a gun. I found it.
it’s the device shown in this post http://forum.audacityteam.org/viewtopic.php?f=27&t=5569&start=10#p80958 that i think is what i want, feel free to tell me i am wrong if you think i am, you know more than i do about this it seems, i am just trying to get you or whoever else would be willing to build me one, bucause not only am i crap in the soldering department, but i seem to have the worst luck in circuits that i build for myself i only need one at the moment, but could possibly want 3 more in the future, if you aren’t willing to do this for me i would just ask for very detailed instruction to create exactly this (assuming it’s what i need, and if not than instructions on what i do need) to pass along to a friend, i’m sorry i can’t quite grasp all the other threads, i am running on about 4 hours of sleep and even when i’ve had 8 technical stuff like this confuses me. lol. but i would be willing to pay whatever price we would both deem resonable (if this is allowed here) to get what i need built for me. i am not much of a DIY guy.
i am not much of a DIY guy.
Then the alternate method may be handier. Record each microphone on its own computer. Anything that will do a Skype call should work so people with netbooks or other smaller Windows machines should be able to handle it. At the end of the show, Export the sound files and walk them over (USB Thumb Drives??) to one computer for integration into one show in Audacity.
Each time you Import a new sound file, Audacity will stack it one on top of the other and play them all at once. Use the Time Shift Tools (two sideways black arrows) to shift each sound file earlier or later until they all match. Audacity will add them all up into one show when you Export.
Make sure to start early and stay late. That is, leave a bunch of time before you start the show and after for time fudging. If you start the show before everyone is recording you can have a bad time in post production matching the voices.
I have posted a product request at Sweetwater Sound. This may be the second time I requested this. I lose track. I send people over to them all the time and I have an account there. I really like their product illustrations and technical details. I don’t have to dig for stuff, so I interrupted their string of promotional messages for a “real” message.
“Look, if you really want to be valuable…”
And speaking of Sweetwater, I have used this AKG microphone.
I used it with the battery adapter, but you can get an adapter that allows you to use it with 48 volt phantom power from a mixer such as your Behringer.
I think I know of one reason Sweetwater isn’t going to be interested in this. We’re not actually converting a gamer microphone into an XLR-3 Male connection. We’re only faking it poorly so that a very short XLR cable can get the performance into the mixer before it starts buzzing and humming.
A real XLR-3 connection such as from a Rock Band Microphone will work with a hundred foot long cable (attached picture). This adapter won’t do that. So the first time a singer tries to use this adapter in a real performance, or you try to use it with long cables, everybody is going to be in deep trouble.
Back on the subject of using the Phantom power…
The IEC phantom power standards says you can draw up to 10 ma.
The standard computer mic connection is 5V through 2.2k meaning the most you can draw is about 20 ma (at 0 volts), but if you want some useful voltage you’d have to be under 10ma.
So all you need is a mechanism to drop the voltage. I would suggest a 4.2 - 10k resistor (for 10 ma or 4 ma max respectively) and a 6V Zener.
However, I agree that at some point it’s better to just go buy a real microphone.
That would be a noisy zener in a microphone circuit? That’s the other problem with working signals in the .001 volt range. That and we still haven’t created a real balanced XLR signal.
Those AKG microphones seem to work pretty well.
Well yes you need a bypass cap on the zener. I doubt it would be any noisier than what is provided by the typical PC. If its a real concern then I’m back to “buy a real microphone”.
I wonder what you would need to do this job for real. Say one of the requirements is the mixer has to supply 48v on pins 2 and 3. Why would you even need the zener? Just keep increasing the size of the load resistor so the “plate current” remains the same. How would you create a balanced signal on 2 and 3?
I know there’s a trick to this. You don’t have to drive both sides, but the impedances have to match…
Well to create a truly balanced signal is going to either need active components or a transformer. The scheme I was envisioning pin 3 would have no AC signal relative to pin 1, and all of he signal would be in pin 2. (There would probably be a fat capacitor between 3 and 1).
A single transistor inverting gain one amp could get you the inverted signal, and easily be powered from the same 48V. However to match the impedances you’d probably end up adding a second transistor as an emitter follower on the mic input so that you could control it’s impedance. (Because you have no idea what the output impedance of the computer microphone is.)
The zener is there for the same reason. You don’t know how much current the computer mic needs, and I would presume that 48V would fry it should it only need 10-20 uA instead of 10 mA. OTOH I just realized that a simple resistor divider will work… The typical circuit in the computer is 2.2K to 5V. A 22k resistor and 2.5k resistor wired as a divider will get you the same thing effectively.
to create a truly balanced signal is going to either need active components or a transformer.
I went to a learned lecture once which refuted that. Almost certainly if you needed a floating sound generator you’ll be pricing transformers — either to generate the signal or to manage the DC, but to get a balanced generator requires equal resistances in the signal and ground legs. Full stop.
Thinking about that is giving me a headache, but I wonder if that can be put to good use. Yes, the output impedance of the system without the zener is going to be roughly the value of the “plate load resistor,” so running the system directly on 48V is not useful. But instead of jamming pins 1 and 3 together (everyone’s natural reaction) build out pin 3 so it matches pin 2 in resistance if not signal.
Line receivers are looking for a difference between 2 and 3 to derive the show. Any difference. So far, so good. Anything appearing on both 2 and 3 is rejected. If the branch resistance on both legs is identical, radiation or other interference on both wires will match.
I think the only thing I’m missing is a “good” microphone’s output impedance of 150 ohms.
That would be rough to do without some very serious work.
Do the DC to DC converters “act like” a transformer in that the current availability goes up when the voltage goes down?
So I think this will work:
It is definitely not balanced and probably won’t run down a long cable without noise, loss or other issues. This design will definitely “pop” when you plug it in (or if you turn the phantom power on/off) so you want to be sure the volume down when connecting.
If you want a balanced output then you need to add a matching transformer like this:
But given a decent transformer is a pretty good fraction of the price of a decent microphone why bother?
PS: The caption on the J2 should read “mini-phone” not “mini-phono”…
PPS: On reading the phantom power spec… 48V power is supposed to have 6.8k series resistance from the source, so in the first design the 22k R1 should probably be 15k. In the second design (since it is effective fed by both legs) R1 should be 18k.
A little web searching turned up this circuit:
Which with a bit of modification would probably work as well.
I also found a significantly more complicated circuit here:
and accompanying explanation here: http://electronicdesign.com/power/modified-phantom-powered-microphone-circuit-reduces-distortion
which is a lot more components, but relatively cheap ones.
Note both of these designs use zener diodes to establish their V+ for the amp circuit, and both use a FET source-follower to create the + and - signals.
So far no store-bought devices?