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Buzzing with mic extension cables

superamazing

superamazing

I've been experiencing a strange problem when I try to wire extension cables into my Rode Videomic. There is a high pitched pulsing sound that I've noticed with 3 of my 4 extension cables. There is no pulsing sound when I attach the mic directly to my recorder. This sound persists even away from electronic sources which could cause interference. And, again, with one of my cables, there is no extraneous sound.

The Videomic uses a 3.5mm jack, so I've been using headphone extension cables. For all my research, I can't figure out if there is a difference between headphone extension cables and microphone extension cables. Maybe this is the problem?

Although one of my cables works, it is not long enough. I bought a new cable, and that one buzzes too.

Any ideas what's going on?
 
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The difference is likely the shielding. Also, I suspect this is an unbalanced line, and with unbalanced lines, the longer the run, the more prone to interference.

superamazing said:
I've been experiencing a strange problem when I try to wire extension cables into my Rode Videomic. There is a high pitched pulsing sound that I've noticed with 3 of my 4 extension cables. There is no pulsing sound when I attach the mic directly to my recorder. This sound persists even away from electronic sources which could cause interference. And, again, with one of my cables, there is no extraneous sound.

The Videomic uses a 3.5mm jack, so I've been using headphone extension cables. For all my research, I can't figure out if there is a difference between headphone extension cables and microphone extension cables. Maybe this is the problem?

Although one of my cables works, it is not long enough. I bought a new cable, and that one buzzes too.

Any ideas what's going on?
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There are more than just electrical wires that can cause interference. Cell phones, wi-fi, garage door openers and other remotes, even poorly shielded refrigerators and similar appliances; oh, and don't forget microwaves. You don't just turn everything off, you unplug them, as "off" is really standby and the device is still drawing and using power.

As GP mentioned it's a question of shielding. That's why professionals use low-z (low impedance) rather than hi-z (high impedance). Also, besides the shielding, low-z signals can travel much further distances without noticeable signal degradation as compared to hi-z.

One more thing that can cause problems are cheap components like adapters or the cheap components used on cheap cabling; they can actually act as an antennae and attract unwanted signals rather than resist them.
 
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i had this the other day and all it was is that it just was a loose connection, even though it seemed connected properly just playing around with the connection fixed the problem. it was a 3.5mm extension cable too. might work!
 
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flourescent lights, dimmers, ceiling fans (really anything with an electric motor) will throw off RF Interference... and power lines running next to your audio line will cause an inductance current as well that sounds the same as the RF interference, the commonality is that it occurs once every 1/60 of a second, the speed of US/Japanese (NTSC) power, or 1/50 of a sec (PAL) everywhere else...

The NTSC/PAL frame rates are based on the alternation speed of the respective power structures, the British empire spread out and brought its infrastructure to the rest of the world... and the US helped Japan rebuild after WWII and brought in its infrastructure to do so (I love it when technology shows us history).

If you have to run power and audio near one another, give plenty of room, and only cross the lines at a 90 degree angle to minimize the possiblilty of an inductance field causing problems.
 
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Thank you all for your quick responses. So, I have a follow up question. Apart from the extra shielding, are the extension cables for headphones and microphones identical? For example, could I use a 3.5mm microphone extension cable as an extension cable for my headphones?
 
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