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I just bought a guitar amp (Blackstar ID Core 40W) and I'm trying to figure out if I should be concerned about some white noise being emitted while a cable is plugged in.

When the amp is on and no cable is plugged in, I don't hear a thing. With a cable plugged in though, with or without a guitar, then it makes a very faint white noise sound. It's pretty difficult to detect when playing, but it's definitely noticeable when it's quiet. Could it be the cable? I don't remember this sound the first few times I played it, but now it seems to be fairly apparent. Turning down gain helps a lot, but doesn't eliminate the problem.

Thanks

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    A guitar cable acts an an antenna and picks up RF noise in environment (and there is a lot). When you turn down gain, you are electrically attenuating not only good (desired) audio signal but also the noise, and turning it up would amplify it. So what is observed is quite normal. Some of the modeling amps have inbuilt noise-reduction to reduce this.
    – bdutta74
    Commented Dec 9, 2016 at 12:29

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All amplifiers hum a little to a certain extent.

However, cables can acquire fairly large amounts of white noise - that depends on external influences. Guitar cables are especially susceptible to acquiring white noise because they are an unbalanced cable.

What is an unbalanced cable?

An unbalanced cable sends one copy of the initial audio signal down the cable. Sending one copy of the audio signal allows external signals to easily warp, shape or join the initial audio signal and is a very well known reason behind creating white noise.

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What is a balanced cable?

A balanced cable has 3 wires within the cable; ground (GND) and 2 audio (AUD1 & AUD2). A balanced cable splits the audio signal and sends one intial copy down AUD1 and then sends another copy with a reversed polarity down AUD2. This makes the signals be out of phase from eachother. Once the signal reaches the other end of the cable, AUD2 gets reversed/inversed again to be the same signal as AUD1.

So why flip polarities?

When the signals with opposite polarities are sent down a cable, external signals warp, shape and join into the signals - just like a balanced cable. However, the noise is inphase to each signal but the signals are out of phase. Therefore, if the signal is flipped again to have the same polarity and substracted from eachother, the noise gets cancelled out from the signal completely and you're left with a clear crisp signal.

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Click here for a more indepth explanation:

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  • You might want to add it explicitly that the guitar cable is basically a large antenna, and it is pickup the ambient RF noise in the environment.
    – bdutta74
    Commented Dec 9, 2016 at 11:58
  • It's limiting to say RF's are the only type of signal that effects the initial - hence, I resolved this to 'external signals'.
    – John
    Commented Dec 10, 2016 at 0:20
  • Thanks for the reply! Is there anything I can do in this case? I live in an apartment downtown, so there's probably a lot of RF interference. Would a different cable help?
    – A4Treok
    Commented Dec 10, 2016 at 12:19
  • There's no way to completely get rid of this. Another way to cause Whitehouse from your amplifier is by not having isolated power. Maybe try using isolated power for you amp :)
    – John
    Commented Dec 11, 2016 at 1:40
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The blackstar I’d core range is notorious for having a background hiss , I have been researching them as I like the idea of stereo recording . It’s a bit of a nuisance .

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