No, a good quality, correctly set up vinyl playback system should be very quiet and exhibit no noticeable hum.
What is Hum?
The term ‘hum’ describes repetitive low-frequency tones of a constant frequency or pitch, usually 50/60Hz or 100/120Hz. Hum can be mechanical or electrical in origin and usually indicates a problem in the playback system. Whatever the origin, wherever possible, hum should be tracked down to the source and eliminated.
Bad earths or grounds commonly cause electrical hum, especially in vinyl playback systems. This is due to their high sensitivity and gain which takes tiny signals like hum and amplifies it to the point where can become a problem. The turntable/pre-amp/amplifier combination must be effectively grounded together and at least one piece ground-referenced, to ensure a quiet system.
Ground loops occur where two elements in the playback chain reference different grounds and therefore sit at slightly different potentials. This causes small currents to flow between them which are heard as hum. Bad cables can play a part here, as some do not have an effective ground linking both ends of the cable structure.
Mechanical hum can originate from turntable motors and mains transformers. The hum from both of these sources can often be resolved with the right attention and some new parts, with specific attention paid to damping and isolation.
Cheap phono preamps, cartridges and cables will always be noisier than good ones and active preamps will always be noisier than transformers. An English brand of turntables that shall remain nameless opts to not use a separate headshell/arm ground. These decks are generally always a little noisier than similar turntables with a better, separated ground. Equipment type, set-up and installation can all contribute to hum.
Mechanical vibration from the turntable itself or from other equipment can be coupled through a turntable, back into speakers, creating what’s called a positive feedback loop. These loops can occur through shelving for example shared by speakers and turntables, wooden floors and other resonant structures.
In these cases, the hum makes its way to the speakers, which energises the turntable, arm, and record and it is then fed back into the signal chain and further amplified. Positive feedback loops can very quickly go out of control and destroy speakers and even amplifiers, so if you have a hum that appears to be coupled through your turntable, resolve it or seek expert help immediately!
A turntable’s spindle and/or motor bearing will also contribute low-frequency noise. This is broader spectrum LF noise, rather than monotonic hum and is called rumble. The cheaper the turntable, the poorer the mechanical quality and greater the tolerances and roughness of these bearings, and therefore the ‘rumblier’ these decks will be!
In really good and well-set-up vinyl playback systems such as my reference system here at Liquid Audio, there is no audible hum. I don’t just mean a little, I mean NONE! The predominant noise in systems like this is groove noise, a residual component of the cutting lathe, and of the friction between the stylus and the groove itself. Some white noise from the amplification is present in all systems, but hum is absent in the best systems.
Customers curious about how quiet a really good vinyl playback system can be should let me know. There’s a chance you can listen to my set-up if I’m not too busy.