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    Strange Speaker problem as speaker picks up noise when any of the swicthes toggled .

    Hai

    I am Using creative 5.1 speakers for my pc ...Now strange problem occurs .If any body turns a switch on or off in surrounding rooms where the pc is connected a strange is heard from speakers how the speaker is picking noise from power line.

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    Re: Strange Speaker problem as speaker picks up noise when any of the swicthes toggle

    Questions,

    1, What sort of noise?
    2, Has it always happened or has it started recently?
    3, If recently have you added a new electrical item?
    4, Does PC have same problem if pluged into a different mains socket?
    5, Does any of the PC audip cables run next to the mains cabling?

    I'm working on the assumption that the PC it's self is mains powered and not a laptop, and the building is small with a "single phase" supply.

    Therefore the PC and the other electrical items being switched are on the same mains phase and ground/earth.

    The most likley cause will be "switching energy" from an item which puts an inductive load onto the mains. This noise is coupled from the mains to the audio stages via the PC power supply or closely coupled low power audio (mic input) or signaling (network etc) cables from the PC being directl adjacent to the mains power in the building.

    The most likley cause for switching noise to make it through the PC's power supply is that for some reason it is running out of specification (load / filter / wiring).

    There are a number of ways for this to happen, however the first thing to rule out is that your mains supply is not at fault by "browning out" (do light flicker etc) or the other items being switched are inductive such as old fashioned fan motors or flourescent lamps with old style balasts.

    The next thing to check is the mains wiring it's self ie are all the lives, neutrals and earths grounds etc connected correctly.

    The next thing to check is what other mains powered equipment is connected to the PC and is that wired correctly. That is does the 5.1 sound come directly from the PC or is it going into a home entertainment system or audio amplifier first?

    Also does the PC do other odd things when people flick switches such as the screen fuzz/flash/blur does it freeze or crash (you might have an underated or faulty powersupply in the PC).

    There is a lot you have to check to get to the source of the problem but by doing things in a methodical manner you can rule things out untill you find the cause.

    My guess in a home with modern equipment will be (providing the audio is wired correctly) that there is a fault with the way the PC powersupply filter is connected to the mains, or similar in another piece of equipment connected to the PC. But I would not rule out other faulty or old equipment such as fans and aircons.


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    Re: Strange Speaker problem as speaker picks up noise when any of the swicthes toggle

    1.Noise only for brief 1 -3 secs when some turn on /off occurs in the surrounding rooms
    2.the problem started a few weeks 4 -5
    3.No New Electrical installations since the problem began
    4.I have to try another socket to plug in ,have n't tried that option
    5. The CPU power Cable runs next to Audio Cable

    ---------- Post added at 12:58 ---------- Previous post was at 12:52 ----------

    Another Interesting question

    Hai I am having the another problem some times ..radio interference ....Let me ask a question can we make use this interference as an indicator for cell phones in the area ...How can we build a circuit to trigger upon the noise ..so that we could make some cell phone sniffer !

    earlier I had tested a cell phone sniffer circuit based on a capacitor loop antenna



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    Re: Strange Speaker problem as speaker picks up noise when any of the swicthes toggle

    Hmm two threads for the price of one 8)

    First thing I'd do is find a switch that is not going to annoy other people if you turn it on and off frequently and use that as your "test signal".

    I'd then move the audio cables away from the power cord and "test" to see if it was just cross coupling.

    Then if that has not solved it if you have a handy "filter mains lead" such as thos you see in computer shops with four or six sockets in plug that in between the wall socket and the computer and "test".

    You may find that the mains side filter in the PC Switch mode PSU is starting to break down, or that the earth/chasis connection in the mains cable / wall socket has gone dry or worked lose.

    Sadly it's a case of "walk the line" testing till you stop it or get a change in charecteristics of the noise to localise the fault (unless you have the appropriate and expensive test gear to just plug in and run).

    But onto the second more interesting thread ;)

    There are various ways cell phones transmit and receive the data that is the phone call these days (that is most analog systems are long gone).

    The main charecteristic distinquishing them is not the RF band they use but the "signal envelope" and how easy that is to detect.

    In some cases (GSM) where the RF signal envelope (not the RF itselfe) falls inside the audio band all that is needed is an unshielded audio amplifier input. The RF signal envelope is "envelope detected (just like any simple AM radio detector) and the resulting audio signal gets amplified as audio and makes a grating grunging noise in the speakers. Thus a very cheap AM radio tuned to a moderatly weak station or even blank part of the band will pick up an adjacent GSM phone.

    However some mobile phones (CDMA) effectivly use a continuous envelope signal and this has to be done in a different way. One is the simple "bug hunting" diode detector. Put simply you have an antenna with a parellel tuned circuit at the center of the RF band used. Any signals will cause an RF voltage to appear across the tuned circuit. A suitable signal diode will convert this RF signal into a DC signal and this can be used to drive a simple meter via a lowpass filter and amplifier.


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    Re: Strange Speaker problem as speaker picks up noise when any of the swicthes toggle

    I use both GSM and CDMA phones ..it seems GSM produces most of the noise ...



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    Re: Strange Speaker problem as speaker picks up noise when any of the swicthes toggle

    I try a shorter comment. Basically it's a matter of bad designed equipment. Either the PC sound card or the Creative 5.1 amplifier (not the "speaker", strictly spoken) is picking up the RF interferences. According to EMI regulations, it shouldn't. As a minor excuse, the field strength of a GSM mobile phone can be considerably above levels required in the regulations. But GSM frequencies are rather easy to filter in a good designed audio system.

    To distinguish between PC sound output and amplifier as interference entry point, you can e.g. disconnect the audio cables from the sound output, but keep it's ground in touch with the connector ground. If the succeptibility persists, it's most likely an amplifier bound problem. If disconnecting the cables removes the problem, you should also try common mode ferrite filters clamped around the audio cable.


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