Reducing Static Noise - Getting an Audio Interface?

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doctor.apparatus
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Reducing Static Noise - Getting an Audio Interface?

Post by doctor.apparatus »

Hello fellow producers,

my problem is the following:
I am using a Condenser Microphone with 48Vpp. . It goes straight onto my onboard sound chip.
When I start Audacity for example and record something I get that hissy white noise in the background. Like one of those old TVs not as extreme as such but as annoying. I get it regardless of plugged in microphone.

I already did some research and some people advised other people to get an audio interface.
I am just a hobbyist not an audiophile so I am happy with the cheapest easiest solution.

PS: I already fiddled a bit with Ardour and created a noise filter, but as you can guess it is not that satisfying...

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English Guy
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Re: Reducing Static Noise - Getting an Audio Interface?

Post by English Guy »

Many sound cards have noisy pre amps. See if you can turn off or down the mic boost (it might be called something different in your system).

If the mic is now too quiet have you something better to boost the signal, even a little amp with a headphone socket as an output?

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CrocoDuck
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Re: Reducing Static Noise - Getting an Audio Interface?

Post by CrocoDuck »

doctor.apparatus wrote:When I start Audacity for example and record something I get that hissy white noise in the background. Like one of those old TVs not as extreme as such but as annoying. I get it regardless of plugged in microphone
Other than a noisy preamp, it could be electromagnetic noise. Internal soundcards are very susceptible to that, especially on desktop computers. All components inside your pc case emit electromagnetic noise due to currents circulating in them. Fans especially, being pretty much coils. This electromagnetic noise gets then induced back in the soundcard circuits, polluting the signal. If your soundacard can be moved around you could try to place it further away from sources of noise. Most noisy components are: power supplies, fans, hard drives. Few people online built a film foil shield around their card: you wrap the card with foil and then connect the foil to a ground point. It works very well (it actually shields from noise) but I would totally discourage doing it: the risk you might short something you don't want and produce irreversible physical damage (e.g. by shorting a high capacitance capacitor by accident) is too high.

An external sound card will probably strongly reduce EM susceptibility of your system, that's why you see them often recommended.
doctor.apparatus wrote:I am using a Condenser Microphone with 48Vpp. . It goes straight onto my onboard sound chip.
Another common cause of spurious signal artifacts is improper circuit coupling. Each circuit has an input impedance and an output impedance. For voltage coupling, the input impedance of a circuit needs to be much higher than the output impedance of the preceding block. It might be that the line input of your sound-card has not an appropriate impedance to accept the signal from your mic or equipment. This will result in increased noise floor, unwanted sound coloration and distortion. You could connect your mic to a simple mixer with 48V and the mixer line output to your soundcard line input. Or use a DI box.

gimmeapill
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Re: Reducing Static Noise - Getting an Audio Interface?

Post by gimmeapill »

That could be a ground loop.
There's a quick and easy way to find out: If you use a notebook, try to unplug the power supply and to run from battery to see if the noise goes away.
You may then get rid of the issue completely with a cheater plug (just be sure to read the note on electrical safety): https://en.wikipedia.org/wiki/Cheater_plug

doctor.apparatus
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Re: Reducing Static Noise - Getting an Audio Interface?

Post by doctor.apparatus »

I have that noise in both cases: plugged in mic and no mic at all.

The circuit is the following

230V->Phantom Power Supply <- Mic
And from the PPS it goes straight into my computer to the onboard sound chip.

artek
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Re: Reducing Static Noise - Getting an Audio Interface?

Post by artek »

I have that noise in both cases: plugged in mic and no mic at all.
Interface is better option for condenser microphone but a new cheap external interface can also produce static hum.

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CrocoDuck
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Re: Reducing Static Noise - Getting an Audio Interface?

Post by CrocoDuck »

doctor.apparatus wrote:I have that noise in both cases: plugged in mic and no mic at all.

The circuit is the following

230V->Phantom Power Supply <- Mic
And from the PPS it goes straight into my computer to the onboard sound chip.
Then I would say it is due to the soundcard. Preamps and electromagnetic noise would be the most probable causes I would say. Can you record a fragment of the noise and make it available? You can attach small files in the forum posts. A 10 seconds of noise in an uncompressed file would be enough. We could check the spectrum and see if there is something obvious (like a 50/60 Hz peak and harmonics typical of ground loops ect...)

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CrocoDuck
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Re: Reducing Static Noise - Getting an Audio Interface?

Post by CrocoDuck »

beck wrote:BTW. Ontipic(?) questing in between...

Could grounding your pc, or the lack of it be the cause of noise??
Depending on the impedance of the ground lines ground loops can develop. In practice, not all the ground connectors of all pieces of equipment have the same impedances. The impedance of the ground rails is supposed to be small, but sometimes it can be appreciated. When this happens different voltage drops develops across the grounding connectors. Given that the ground is the reference of the power supplies, these drops oscillates with them (50 Hz or 60 Hz in USA) giving rise to humming noise in other pieces of equipment for which, due to a different voltage drop to ground, the ground point is slightly different. The use of a filtered plug can improve a lot, together with electronics designed for ground loop breakage (by separating the grounding points of the various pieces).
beck wrote: How many have there pc pluged in a wall socket without grounding? (so not grounded pc)
All the people with an unplugged laptop running on battery :wink:

So, in short, yes: the way your pc (but also the rest of the equipment) is grounded can be source of noise as soon as all the ground points that are supposed to be the same end up not being the same due to the voltage drop across their ground rail.

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Re: Reducing Static Noise - Getting an Audio Interface?

Post by gimmeapill »

Yeah, no big deal most of the time: I've played for many years with a desktop un-grounded via a cheater plug.
Simply because when you're partying in the woods with power coming from dodgy generators, that's often the only way to play at all (truth saying, getting an electric shock was anyway a minor concern in those days ;-))

Yet there's a slight difference between a techno live set with a mid controller and an electric guitar: With the guitar, when you touch the strings, you are the path to the ground. Electric shocks from guitars are not unheard of, especially when you add a microphone.
So I would probably think twice with that setup...

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English Guy
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Re: Reducing Static Noise - Getting an Audio Interface?

Post by English Guy »

gimmeapill wrote:. Electric shocks from guitars are not unheard of, especially when you add a microphone.
So I would probably think twice with that setup...
People have died from this. If you touch a guitar and microphone and one is live the shock goes through the heart.

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CrocoDuck
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Re: Reducing Static Noise - Getting an Audio Interface?

Post by CrocoDuck »

beck wrote:That when gear has (and so needs) grounding u should use it. So when a power plug has grounding only plug in in a grounded wall socket.
This because i think that when something is grounded the developers of that gear use that grounding for a proper functioning of the device. They probably have used the grounding to prevent developing noise interference.
Always always plug your components the way they are supposed to be operated by the manufacturer. You are absolutely right on this point or else
English Guy wrote:
gimmeapill wrote:. Electric shocks from guitars are not unheard of, especially when you add a microphone.
So I would probably think twice with that setup...
People have died from this. If you touch a guitar and microphone and one is live the shock goes through the heart.
Ground loops arise when the basic assumption on grounding does not hold due to various reasons, that is: when I plug something to ground the impedance between "equipment circuit ground point" and "actual ground point" is not actually very low (< 1-2 Ohms). This can happen for cause completely external to the equipment circuitry. For example, it could be due to the use of long cables.

If you need to break ground loops use dedicated equipment. For example, this DI box have a ground loop prevention switch (GND Lift) that will keep separated grounds of the signal paths to avoid ground loop hum to leak in the audio. Notice that all these circuitry operates on the reference of the signals to prevent ground loop manifestation, they are not supposed to operate on the power rails.

I want to stress this again: for your own safety only use your devices as intended by the manufacturer. Don't attempt any crazy thing to break a ground loop, use only equipment designed to do so.

As a note, transducers (microphone and mics) are very sensible to ground loops. Especially condenser and electret microphones due to the small mass of the diaphragm and the fact that they are electrically charged or biased, yielding to high sensitivity of the device to electromagnetic disturbances. For this reason, induction from fluctuating ground can be very evident.

gimmeapill
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Re: Reducing Static Noise - Getting an Audio Interface?

Post by gimmeapill »

English Guy wrote:

gimmeapill wrote:
. Electric shocks from guitars are not unheard of, especially when you add a microphone.
So I would probably think twice with that setup...

People have died from this. If you touch a guitar and microphone and one is live the shock goes through the heart.
All in all, that can be considered an honorable end for a true rock star.

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kbongosmusic
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Re: Reducing Static Noise - Getting an Audio Interface?

Post by kbongosmusic »

You say 48Vpp. This must be a reference to phantom power. Condenser mic's can require a bias operating voltage(phantom power), something like 48v. My better condenser mics require this and I get that from a small mixer that has 'phantom power'. This high voltage is somewhat historic, and often something less will work(like 9v say).

The actual mic is only going to put out a weak signal. And this often requires a pre-amp to boost it up to a sweet spot. So you will notice on inexpensive mixer like my behringer eurorack there is an extra pre-amp to boost this on a few of the channels that can plug in a 3 terminal balanced connector(which most condenser mic's use).

Now, audio interfaces built into computers are bare bones basic. They don't normally come with 48v phantom power. When you used to add a sound card they might include 2 connectors for input - a line in, and maybe a mic in. If you have a laptop, it maybe just a mic in. These are generally designed for headsets that include a basic electret mic, they have only a 2 wire interface and generally have a 5 volt bias that is needed by the electret mic. The electret mic is similar to the condenser mic in it's need for a bias phantom voltage to power it, but it's generally an easier to obtain 5v bias power.

So, try to tell us the equipment you have better - are you dealing with a desktop computer? Does it have a line in? Or is it a mic input(generally mono)? Is this a 1/8" connector? Or is it a laptop? Does it support stereo or is it just mono?

My suggestion would be to try and record something with a line level output, like plug in a cd player. Can it get a good recording without noise from that? If not then there is little hope to getting good audio from a mic that is generally more of a weak signal and require things like pre-amp, phantom power, etc. And this would not be to big of a surprise because of the basic bare bones provisioning on a built in audio input to a PC or laptop and all the noise built into a computer.

You can find inexpensive USB audio adapters that provide decent enough sound input. Like a behringer U8xxx. But the condenser mic is problematic in it's need for this phantom power, and often need the extra pre-amp built into say my eurorack to hit the sweet spot that your audio interface has best ability. The more expensive interfaces like focusrite, presonus have things like phantom power, 3-line balanced inputs, pre-amps. Unfortunately there is not much in-between if you are on a budget that have these needed items for condenser mics. A USB condenser mic might be something to consider if you don't want to spend $100 or more on a nice interface or mixer. But these are not real cheap either, but they do avoid mixers/pre-amps/phantom power.

Beno27
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Re: Reducing Static Noise - Getting an Audio Interface?

Post by Beno27 »

Might get shot down in flames, but have you considered a USB mic? If you don't want to buy another mic then that's fair enough but there are some good options there that don't cost the earth.

Some of my favorites in here if you need a recommendation: http://subreel.com/best-usb-microphones/

If not, I further the DI box suggestion, they are super cheap as a piece of kit too.

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