A Decibel Dungeon specification page

Here are the specifications for two stepped attenuators. Both are designed around a 24 position rotary switch. Use a make-before-break type.

The maximum cut of around 54db is enough for the 'Decdun' project system and should be enough for systems that do not have an excessive amount of gain. Most of the steps are about 1.5 db, with larger steps at the lower volume settings which you will seldom use. There is no mute position as it uses up another position on the switch and in the 'project' system the selector switch provides a mute option anyway.

The resistor values quoted are available for the Welwyn RC55 and RC55C range. If you do want to use 1% metal films, choose the closest value. Because you have to buy larger quantities of the metal films, typically 100, it is often as economical to buy the better quality Welwyns.

The first design has an impedance which varies between 15 and 30K and the second an impedance which varies between 59 and 134K. I have found that both will work equally well in the 'project ' system.