DIY - Side Round
Amplifier Buzzzz/Hummmmm.... Dealing with line noise..
So you plug your new amplifier in and it's awesome. Until you hear an annoying humm or buzzzz - the line noise sound that is constantly there, or tied directly to increasing the volume.
I've had a couple people reach out to me about line noise, and I've also ran into it with testing amps myself. Generally it hasn't been a big problem, and most of the time it's not going to be an issue. But if you do run into this, then the good news is it can be an easy fix. As I've mentioned before I'm not an engineer, and I don't often stay at Holiday Inn's sooooooo...... Here is some research and testing I was able to do to come up with some layman's results.
First off - this humm can be associated with a few things.
1 - The amplifier itself, and the circuitry it uses to process and amplify the input signal.
2 - The power supply, some of the cheaper power supplies can create issues. Different power supplies plugged into different amps tend to produce differing results. (probably related to ground loops listed next)
3 - Ground loops and power line noise. This is basically noise that finds it's way into your audio signal going from the pin to the amp. This can happen for a ton of reasons. Take a look at the first 8 minutes or so of this video as it does a good job of explaining this:
Let's dig a little deeper...
#1 - Amps have a certain amount of noise to them. It's just a fact of life. Since we are not working with $5,000+ audiophile amps(and why should we be) we will need to expect some level of noise. But there is some great news here, most of these mini amps are absolutely just fine and the noise is no where near a problem. It's the other two problems that are usually the issue and not the amp itself. In order to quickly test your amp, plug your amp into your speakers and power supply - turn the amp on and cycle the volume up and down(be sure to turn all the dials up). Do this without any type of cable or audio signal plugged into the amp, only the speaker cables, and power power cable. That is generally going to be your noise floor you are working with, and it's probably more than acceptable. (odds of this being your noise problem - low)
#2 - Power supplies, yuk.... This has become a bane of mine. I have a bunch of amps laying around, and also a bunch of power supplies that came with them. I don't always plug the same power supply into the same amp when I'm sitting on the floor switching between amps. One amp maybe sounding great, then I switch it up, and plug that amp back in later and its full of noise. WTH - turns out, each amp reacts differently to different power supplies. Soo a good learning moment. If you do the test above, and you get some noise - then try switching the power supply, if you have another one available. If you have to purchase your own power supply to begin with - then consider spending just a little more on a quality power supply. (odds of this being your noise problem - low/mid)
#3 - Ground loop noise. First watch that video I posted for a better overview of ground loop issues, and noise that can get into your audio signal. Do the test I mentioned in #1 above. Sound good to you? Now plug your audio cable into the amplifier. Was the amp quiet and now you hear the noise? (odds of this being your noise problem - high)
With #3 being the most likely cause of your noise problem - what can you do? First, try plugging your amplifier into the same outlet as your pin(Even the service outlet inside the pin could help). Second, try a different power supply if you have one available. Third, go to amazon and purchase a $10 3.5mm ground loop noise eliminator: https://www.amazon.com/dp/B06XQYN77L and plug it inline with your audio signal. More often than not, the ground loop eliminator will do the job, there have been times when it has made the noise worse depending on the power supply.
When I get to the amplifier writeups and comparisons - I will be sure to mention it's line noise level, and any specific fixes that worked.
With these steps, and some mixing and matching trials, you should be able to greatly reduce any levels of line humm/noise you may be running into.
Hope this helps.
***Note: there are some amplifiers that use sound circuitry to temporarily "Mute" an audio input signal when it doesn't detect an input. That means it is like an on/off switch for line noise that maybe present. This is both good and bad. You won't hear the line noise just buzzing away when there is no sound to be played as it will cut itself off. On the other hand, that noise is still there when the sound is being played and it is turned on. This can be annoying during moments when there are passages in the audio when you can clearly hear the noise just buzzing in the background. Think of it this way - Listening to Offspring and you will probably not hear the buzzing because the sound is non-stop. Listen to Phil Collins In the Air Tonight - and you will be hearing all that buzzing in the background.