PS AUDIO: Perhaps the most expensive option a designer has to control the gain is called a stepped attenuator.


Paul McGowan writes: Perhaps the most expensive option a designer has to control the gain is called a stepped attenuator.  These devices can range from the reasonably simple to the ultra exotic and expensive.

Cello’s 59 step platinum attenuator as well as Ayre’s 66 stepped device are exotic, expensive hand built beauties that exemplify the state of the art in volume control through a switch, rather than a pot.  If you’ll recall in our post on pots, we discussed how the potentiometer is the most widely used volume control yet because of the way it’s made, is also the worst sounding of the available options.  If the designer is going to use a resistive divider to control the volume, then a stepped attenuator can be the best option available.

A stepped attenuator is a simple multi-position switch that allows the user to change the volume by switching in (typically) a different combination of two resistors for each volume step.  The more steps available, the more exotic the switch itself.  Here the designer must pay close attention to the contact materials of the switch choosing between simple nickel, to silver, gold, rhodium or platinum depending on the budget and the sonic preferences of the designer.

A stepped attenuator can also be built with relays (which are just magnetically operated switches) and many high-end preamplifiers that include remote control use relays instead of a mechanical rotary switch.

The downside of a switched attenuator is the same as that of a pot: it adds a sonic signature.  In fact, anything you place in the signal path is going to have a sonic signature that changes the music from what it was to something else.  A pot or stepped attenuator can only degrade the signal it cannot make it better.  The stepped attenuator has a very small sonic signature while the pot a larger one depending on its construction.