What is operating voltage?

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firebat

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While shopping for 3.5mm microphones, I usually see an Operation Voltage listed in the specifications. This value usually ranges from 1.5V to 4.5V.
What is this Operation Voltage? Will it affect the volume of the output? Is it better to have a lower or higher voltage?
 
Some microphones require a power supply.
Usually in the studio it's 48vDC/phantom power.

Some mics for cameras and that type of thing require a supply, often supplied by batteries or by the camera.

One isn't better than the other; It's not that kind of statistic. It's just whatever the mic requires.
 
A more common name for "operating voltage" is "bias voltage". Most small mics use electrets (sort of a mini condenser mic) and that voltage serves a similar function as the phantom power in their big brothers.
 
You might be looking at mics for video cameras. The cameras will sometimes provide the voltage to run the Mic, I would assume you need to match the Mic to what the camera can provide.
 
Yes. I don't know how operating voltage relates to headroom.

It's not a sarcastic "no it doesn't" challenge. I just don't know. :)
 
Do take note that phantom power can only be transferred through XLR cables. Not the XLR to 3.5mm one.

And I'm curious too, I've never heard anyone say about headroom relating to voltage
 
I'm afraid mine WAS meant to be sarcastic. I wondered if matkatmusic missed the fact that we were talking about bias voltage.
 
Ok then gents. Headroom and supply voltage 101 coming up!

Take a very familar device, the humble guitar pedal. These normally use a 9volt PP3 battery. I shall take that as 10volts cos' it nearly is with a fresh batt and it makes my head hurt less.
The absolute maximum voltage that pedal could put out is 10volts Peak to Peak. Think of a sine wave with the positive peak just at 10V and the negative at 0volts, of course it could, probably would clip, but the P-P voltage still cannot exceed 10V.

But, all the signal voltages you ever read about are "rms" values. That is 1/2 the P-P voltage times 0.707, thus the rms maximum would be 3.535volts...BUT! The electronics can never hit the internal rails and so we would be lucky to get 8V P-P giving us a resultant rms output of 2.828 volts. If we double the supply to 18volts we would double our max rms output to 5.656V (actually we might do a bit better than that, depends on the circuit devices)

But we must be careful in the case of the electret mic. It might well be that they all run on the lower voltage and a dropper resistor, possibly also a Zener is used to provided higher ratings. The signal headroom would then be just the same.

On a related subject the poor results some folks report from cheaper gear is often a function of lower internal supplies. "Pro" kit generally runs op amps at +18-0-18 volts but as you drop volts you drop costs, (caps, transformers) so many cheaper mixer e.g. have +&-12volt rails. This does no harm so long as you don't drive them too hard!

And you don't HAVE to use XLR for phantom power, any 3pole circuit will do. NOT advised! But it will work. You don't of course need spook juice for an "electret" mic!

Dave.
 
Bobbsy said:
I'm afraid mine WAS meant to be sarcastic. I wondered if matkatmusic missed the fact that we were talking about bias voltage.
Click to expand...

Ah well! I had assumed that was an oversight and peeps really mean the supply voltage? (which it is).
As I just pointed out, you don't need a "bias" or "polarising" voltage for an electret mic.

Dave.
 
Dave, I don't even know enough about it to ask sensible questions, but I figured whether a mic runs on a 12v supply or 48v supply, the output would/could potentially be the same. Is that not so?

ecc83 said:
But, all the signal voltages you ever read about are "rms" values. That is 1/2 the P-P voltage times 0.707, thus the rms maximum would be 3.535volts...BUT! The electronics can never hit the internal rails and so we would be lucky to get 8V P-P giving us a resultant rms output of 2.828 volts. If we double the supply to 18volts we would double our max rms output to 5.656V (actually we might do a bit better than that, depends on the circuit devices)
Click to expand...

I mean, I get this (on the most basic of levels) but isn't the operating voltage of a mic a totally different thing to the power supply of an amplifier?

A capacitor mic's output is created by fluctuations in capacitance, isn't it? I figured within limits any voltage is enough to allow that measurement to be taken, or signal to be created.

Take this as questions from a total noob, please.

PS: Whoever is being sarcastic, can we set it aside for a second? It doesn't translate well into text.
At least do a :p or something.
 
Lt. Bob said:
unlike the sarcastic "are you serious" response.
Click to expand...

Twas not so intended. I just did not want to launch into verbiage and be painted a dick! (I am perhaps a simpler soul than you might think Bob?)

A capacitor mic cannot be made to function without an amplifier. Any amplifier has an MOL and that is related to supply volts.

Dave.
 
ecc83 said:
Twas not so intended. I just did not want to launch into verbiage and be painted a dick! (I am perhaps a simpler soul than you might think Bob?)

A capacitor mic cannot be made to function without an amplifier. Any amplifier has an MOL and that is related to supply volts.

Dave.
Click to expand...

OK, fair enough.
You're not talking about preamps here, right? This is an amplifier in the mic's circuitry?

What would the amplifier in a typical 48v capacitor mic operate on?
Is it fair to say the polarising voltage (within reason) has no effect on headroom, or is that still just wrong?

Thanks for taking the time, Ecc.
 
Steenamaroo said:
OK, fair enough.
What would the amplifier in a typical 48v capacitor mic operate on?

Is it fair to say the polarising voltage (within reason) has no effect on headroom, or is that still just wrong
Click to expand...

My geek side is curious as well.
 
In a condenser, t total voltage output of the capsule itself is dependent on the phantom voltage, but this doesn't really limit the dynamic range of the microphone. It just makes it quieter or louder overall. In an electret, the capsule is permanently charged on its own, with no need for outside power to do its transducer thing.

But both condensers and electrets have active circuitry to buffer and/or amplify the signal a bit before it goes down the cable. These circuits will have their dynamic range impacted by the phantom voltage, though the fact that the capsule's output also changes with the supply (in the condenser at least) kind of makes my head hurt...
 
jimmys69 said:
My geek side is curious as well.
Click to expand...

A friend of mine once told me his geek side was female.
I never knew what to make of that.


ashcat_lt said:
In a condenser, t total voltage output of the capsule itself is dependent on the phantom voltage, but this doesn't really limit the dynamic range of the microphone. It just makes it quieter or louder overall. In an electret, the capsule is permanently charged on its own, with no need for outside power to do its transducer thing.
Click to expand...
This is kinda what I thought.

ashcat_lt said:
But both condensers and electrets have active circuitry to buffer and/or amplify the signal a bit before it goes down the cable. These circuits will have their dynamic range impacted by the phantom voltage, though the fact that the capsule's output also changes with the supply (in the condenser at least) kind of makes my head hurt...
Click to expand...

This I just didn't know about.
Thanks everyone.
 
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