Stepped Attenuator
Our Micro, Desktop, and Balanced Home line of HeadRoom amplifiers come standard with a very high-quality Nobel or Alps continuously variable [smooth operation] volume potentiometer. But the process of putting an audio signal through the gross wipers and conductive elements of a typical continuously variable potentiometer does very slightly degrade the sound in ways that are hard to hear but can be measured in lab bench tests. One way to avoid the small sonic degradation from a typical volume pot is to use a high-end stepped attenuator, which is simply a multi-pole switch that allows you to select a discrete series of resistors (steps) to adjust the volume. You will normally feel a satisfying little click with each volume step. The stepped attenuator also avoids the minor left/right channel level imbalances heard at very low volume settings with the continuously variable pot. However, some listeners still prefer the continuously variable pot design since it offers a finer gradiation of volume adjustments.
There are a couple of different ways to construct a stepped attenuator volume control; HeadRoom builds a 'shunt' attenuator where the voltage is divided between a single fixed resistor on the circuit board and the resistor selected by the stepped attenuator. We prefer this method as keeps the number of contacts the audio signal has to go through to an absolute bare minimum.
We utilize parts from the well-regarded Elma Type 04, 24-position switch, but we manufacture our own Electroless Nickel/Immersion Gold (ENIG) switch contact circuit boards right here in-house; it's just a fancy way of saying that our boards are highly corrosion resistant, and use a very heavy gold plating -- significantly heavier than normal 'audiophile-grade' circuit board gold coatings. This is crucial to vastly increase the expected lifetime of the switch and to provide the purest signal conductivity available for this high-end potentiometer design.