The Systematic Approach Blogs by Steve Elford – Part 9 'The Tracking Error Concept'

Here's one more concept to chew on - tracking error.

“Oh no”, I hear you groan. But after my last blog in which I discussed transparency, we have to add one more critical concept - tracking error. Let’s start with why. You see, the transparency ‘with lenses’ debate is great, it really helps to get the idea of the weakest link in a string of components. But glass is passive, it doesn’t have to do anything to the image other than let it through. However, most of the components in a hifi don’t just let the music through in that simple sense, they change it in some way. Like digital to analogue in a DAC, or amplification with a power stage following a preamp stage say. But also, the ‘transparency’ of one component can be affected by other components around it, like a bad mains conditioner for example

The tracking error concept takes care of this. Vinyl fans will be used to the idea of a cartridge tracking a grove. If the stylus does not follow faithfully the shapes in the groove we hear the tracking error. And if the cartridge is mated to a badly matched tone arm we might expect the tracking error to be worse – a good example of one component’s tracking error being increased by the inferiority of another. Then consider that the turntable might be poorly damped, feeding vibration into the cartridge via the arm and the vinyl itself via the platter. This is adding colouration that is also making the signal from the cartridge less close to the ‘truth’ in the groove, so in essence more tracking error again. And the truth is a useful way of describing the start point in each little process. The truth of the data on an optical disc, or the truth of the analogue signal on the inputs to a power amp.

In my earlier blogs I talked about EMI/RFI and microphony, and these are three of the processes that create tracking error. But there are more of course, such as intrusive correction software or poor power supplies. And as we start to consider the presence of these processes we can use the tracking error principle for diagnosis and upgrading decisions. So the whole discussion about the systematic approach and the systems operating environment can be looked at from the tracking error point of view. Which components themselves exhibit tracking error? Which components are affected by others? What changes and investment in upgrades will take the development of sound quality in a genuinely positive direction? Hm, sounds like the topic for my next blog!