Unwanted audio noises

Or… “Chasing Hum and Buzz and Pops and Hiss, oh my!”

Unwanted noise in your vintage audio gear can be difficult to track down, but a better understanding of how to evaluate the noise and identifying the type of noise itself will give you a head start on finding it’s source.

First, let us define the most common unwanted audio noises. Understand that all of these sounds (except Pops) are present in all audio gear to some degree, the trick is get make them quiet enough in your system to not be annoying.

Definitions

1. Hum.
   Hum is a constant low frequency sound. In places with a 60 Hz AC system, it sounds like (insert sound here) and in 50 Hz places it sound like (insert sound here).
   Note the 50 Hz hum here is synthesized, so it sounds too “clean”. The 60 Hz sample is an actual captured hum sample.
   If you look at these on a scope, they look like this:
   
   Hum is typically caused by ground loops, poor/bad signal wiring shielding, or radiated emf.
   
2. Buzz.
   Buzz is a cousin of Hum, but is more “raspy” sounding, and usually twice the frequency of your AC mains, eg 120 Hz in the USA.
   In places with a 60 Hz AC system, it sounds like (insert sound here) and in 50 Hz places it sound like (insert sound here).
   If you look at these on a scope, they look like this:
   
   Buzz is almost always caused by power supply issues, typically bad filter caps.
   
3. Pops.
   Pops are random spitting noises, usually at a fairly low volume but quite objectionable due to there random nature.
   (insert sound here)
   
   Pops are usually caused by bad connections or old resistors that have moisture in them. In vintage tube equipment, it’s often the plate or cathode resistors.
   
4. Hiss.
   Hiss is a random full spectrum noise, very similar to inter station FM radio hiss. It’s technically a white noise, which is an equal energy per frequency noise, so it sounds “tizzy” and “bright”.
   With no sounds playing and the volume up enough, if you bring your ear near your speakers tweeter , you will hear hiss . (Be very careful to not accidentally play something with your ear there, you can damage your hearing.)
   (insert sound here)
   
   

Diagnosis

Since all these noises are routinely present in some amount, you must evaluate the noise levels in your system and listening room as to how objectionable they are. For example, high sensitivity speakers will expose a lot more of these noises than a lower sensitivity ones will. And you should still do this evaluation even if you have test equipment, as it is common to have a piece of gear that meets it’s manufacturing specs but still has noise issue in your listening environment.

Lets look at how to do this evaluation. First turn your system on and play some music on your usual source at your typical preferred loudness level in your usual listening spot. Now pause the music, and listen for any objectionable equipment noise.
If you don’t hear any, great! If you do, note which noises are present, and whether they are in one or both/all speakers.
Next, lower the volume, switch to your next source, and repeat your evaluation. Continue until you’ve checked all your sources. Now you have a list of any problem areas and how many channels are involved, two major clues you’ll need to track down the issues.

(EDNOTE: Discuss close to speaker eval, also can confuse mechanical hum with electrical.)

Last Updated on 2024-03-11 by Daev Roehr