The Digital Potentiometer

Volume control is often neglected, but is the first element through which sound passes. Mechanical potentiometers are the sources of many noise, crackling and failures. The digital potentiometer presents much better performances, without failures, noises or crackling.

 
The constitution of a mechanical potentiometer

The volume control is often neglected but is a critical component in high end amplifiers. The problems with mechanical potentiometers Potentiometers, offently referred to as "pots", are adjustable resistors permitting to select only a part of a signal.They are generally used for volume control.

A mechanical potentiometer is mainly composed of:

  1. A shaftWhich moves a contact (a wiper) across a resistive element when it is turned, thus changing the volume,

  2. Tree electrical connectionsTwo for the resistive element and one for the wiper,

  3. A resistive elementGenerally composed of carbon, to which the wiper moves, picking up only a part of the signal,

  4. A metal casingProtecting the potentiometer from the environment.

 

Mechanical potentiometers drawbacks

The motion of the wiper across the carbon resistive element involves friction, and leads to potentiometer aging, wear and noise. Moreover, this movement creates a noise called "fader scratch", which can cause audible noise when moving, and gets worse with age. Because it is not sealed, dust infiltrates inside and increase the scratch. The best quality potentiometer only lasts a thousand rotations before showing signs of weakness. This may sound a lot but it comes fast. Lastly, it is very difficult to control the resistance of the resistive element, this explains why in stereo applications, the two resistive elements are never perfectly identical. This lead to a mismatch in volume between the two channels.

 

Why digital potentiometer

The Monange's digital potentiometer circuit offers superior performances in a number of ways:

 

  • Better channel balanceAnalog potentiometers are specified for up to 20% channel imbalance. It is necessary to test and select them, but with no guaranty on the performance degradation due to aging. On the other hand, digital potentiometer can achieve very low channel imbalance, are not subjected to aging, and require no calibration.

  • Dust and moisture proofMechanical potentiometers have the problem of moisture and dust. Because they cannot be completely sealed, dust and moisture affects the linearity and electrical contacts. Digital potentiometer are completely sealed and are in no way affected by bust, humidity, moisture and temperature.

  • No mechanical partsThe mechanical parts of potentiometers are getting used, thus making noise and distortions. In digital potentiometers, there are no moving parts, so no mechanical wear and no need to change them regularly.

  • Intelligent Combined with the Smart Bias technology, digital potentiometer allows intelligent start up and shut down, and feature smooth volume change.

 

A word about distortion...

The digital potentiometer has a THD of 0.0004%, well better than that of an analog potentiometer, you will not lose any part of your precious sound. The sound never passes through a digital circuits, it's all analog, only the control circuit is digital.