Audio Noises

[StephanVolkmann]

Hi,

when i hear audio with my PC, there come a terrible noise with 100HZ or so lokks like mains hum.

when i put my fingers on the wings from the vent of my grafics card to stop the wings, the noise goes a way.

the fan is connectedt by 4 wire, 12V DC fixed, the other 2 wires various 12V DC right?

wherefrom comes the noises, and which way takes they to my audio output?

Both Stereo Speakers are having seperate 230V AC, are Adam Audios Active Studio Monitors

connected at rearpanel on mainbord with an audio jack, one spaeker is connected to the other with cinchcabel

wherefrom comes the noises and how to cut them off?

cu, stephan

 

[mariush]

Computer fans with 4 wires don't have a fixed rotation speed, they adjust their speed based on a signal that comes from the motherboard or the video card.

The four wires have the following purpose (they're not necessarily in this order in the connector):

1. 12v input  (powers the circuitry and the motor of the fan)
2. Ground
3. Speed sensor (the circuitry on the fan tells the motherboard or video card how fast the fan spins through this wire, by sending two pulses for every rotation to the mb/video card
4. PWM  - a cable through which the motherboard (well, a chip on the motherboard) tells the fan to adjust its speed.

The PWM is short for pulse width modulation - think of it like a on/off switch.  The motherboard tells the fan 60-100 thousand times a second to turn the fan on or off ... by playing with the periods of time the fan is on and off, the speed changes, because even when the fan is off, it still spins a bit due to inertia.

You can force the fan to always stay at 100% speed by disconnecting that PWM wire from the connector on the video card.  I can't be 100% which one that is, but usually  12v is a red or yellow cable and ground is a black cable.  The other two wires are the sensor and pwm wires, and nothing bad will happen if you disconnect the wrong one.
In worst case, if you disconnect the speed sensor, the video card won't turn on because it won't be able to know if the fan works or not, and will protect the processor on it from overheating.  If this happens, you can just connect the wire back to the connector.

But anyway, the 100Hz hum is more indicative of a bad input to the speakers but I have no clue why it would change if you put your fingers there.  Maybe you shield the audio cable from pc with your hand without realizing?

[Maister]

Hum in your audio is always most likely to EMI issues which are injected through the signal cable..

Try moving all your cables behind you PC and listen to the hum. Like mariush said you may be shielding the source of interference when touching it. Try touching the case of your PC and see if the hum disappears as well.

[StephanVolkmann]

Computer fans with 4 wires don't have a fixed rotation speed, they adjust their speed based on a signal that comes from the motherboard or the video card.

no, i think thats pwm what you mean,12V+, grnd, sense and pwm like 20KHZ

many fans in Graphic cards and Powersupplys have a 4 wire with

1. 12v
2. grd
3. 12
4. grd

so is not usual to replace with a standard CPU or Casefan with 3 and 4 pin 

The four wires have the following purpose (they're not necessarily in this order in the connector):

1. 12v input  (powers the circuitry and the motor of the fan)
2. Ground
3. Speed sensor (the circuitry on the fan tells the motherboard or video card how fast the fan spins through this wire, by sending two pulses for every rotation to the mb/video card
4. PWM  - a cable through which the motherboard (well, a chip on the motherboard) tells the fan to adjust its speed.

SMB, this chip tells bios something about speeds temps and so on

The PWM is short for pulse width modulation - think of it like a on/off switch.  The motherboard tells the fan 60-100 thousand times a second to turn the fan on or off ... by playing with the periods of time the fan is on and off, the speed changes, because even when the fan is off, it still spins a bit due to inertia.

You can force the fan to always stay at 100% speed by disconnecting that PWM wire from the connector on the video card.  I can't be 100% which one that is, but usually  12v is a red or yellow cable and ground is a black cable.  The other two wires are the sensor and pwm wires, and nothing bad will happen if you disconnect the wrong one.

On my hamegoszilloskop i see on both wirepairs DC signals, no pulsed things
 
In worst case, if you disconnect the speed sensor, the video card won't turn on because it won't be able to know if the fan works or not, and will protect the processor on it from overheating.  If this happens, you can just connect the wire back to the connector.

But anyway, the 100Hz hum is more indicative of a bad input to the speakers but I have no clue why it would change if you put your fingers there.  Maybe you shield the audio cable from pc with your hand without realizing?

After opening the case, i found out that the GPU-Cards Fan is clackering, disconnecting kills the noises

thinking i have to organize a new curler and this thread can become close

[Sm58]

Hi,

when i hear audio with my PC, there come a terrible noise with 100HZ or so lokks like mains hum.

when i put my fingers on the wings from the vent of my grafics card to stop the wings, the noise goes a way.

the fan is connectedt by 4 wire, 12V DC fixed, the other 2 wires various 12V DC right?

wherefrom comes the noises, and which way takes they to my audio output?

Both Stereo Speakers are having seperate 230V AC, are Adam Audios Active Studio Monitors

connected at rearpanel on mainbord with an audio jack, one spaeker is connected to the other with cinchcabel

wherefrom comes the noises and how to cut them off?

cu, stephan

 

so your speakers are active ones. by the way, we love our adams here in the studio.. great speakers ... anyway.

first check if your speaker are pluged into the same ac wall connector as the pc power suply is, to avoid ground loop.

[Sm58]

emi could be the other problem.....

 a bad ground/chassi connection on your audio card or speakers or interconnection (cable inside pc) with a bad screen connection could cause pick up humm

[StephanVolkmann]

Hi,

when i hear audio with my PC, there come a terrible noise with 100HZ or so lokks like mains hum.

when i put my fingers on the wings from the vent of my grafics card to stop the wings, the noise goes a way.

the fan is connectedt by 4 wire, 12V DC fixed, the other 2 wires various 12V DC right?

wherefrom comes the noises, and which way takes they to my audio output?

Both Stereo Speakers are having seperate 230V AC, are Adam Audios Active Studio Monitors

connected at rearpanel on mainbord with an audio jack, one spaeker is connected to the other with cinchcabel

wherefrom comes the noises and how to cut them off?

cu, stephan

 

so your speakers are active ones. by the way, we love our adams here in the studio.. great speakers ... anyway.

first check if your speaker are pluged into the same ac wall connector as the pc power suply is, to avoid ground loop.

yes, its a pair of Adam A3X for 400.- bugs, but needed assist by an sub for deeper sounds

a  pair of Adam A5X for 700 is better solution, cause this need no assist by subwoofers

The adams produce a clean sound at 100% volume, blowing all papers from the desk..

[Sm58]

1) is the problem there from the first installation? or does it come up somtime later?
2) what soundcard do you use? does it have balanced outputs?
3) are all speakers (L, R, Sub) AC plugged into the same wall connector as the pc is?
4) what sub do you use
5) how do you interconnect the L, R, and Sub
.....

if the problem appear sometime after the installation, it's probably a bad ground connection somewhere...
PC Soundcard, chinch cable, L/R/Sub speaker

[Sm58]

The adams produce a clean sound at 100% volume, blowing all papers from the desk..

how do you adjust your volume?

btw
be careful with your ears... you only have one pair.... no repair is possible.

[Sm58]

connected at rearpanel on mainbord with an audio jack, one spaeker is connected to the other with cinch cable

they (a3x) do not have jack (Klinke) sockets... !
Balanced xlr or unbalanced chinch (rca)?
the interconnection between the speakers is just to link the volume knob on the front!!!

[StephanVolkmann]

connected at rearpanel on mainbord with an audio jack, one spaeker is connected to the other with cinch cable

they (a3x) do not have jack (Klinke) sockets... !
Balanced xlr or unbalanced chinch (rca)?
the interconnection between the speakers is just to link the volume knob on the front!!!

the problem is solved, noises comes from the Graphiccardfan have to put a new in

Ps.:

where is the button to mark the thread as solved?