Choosing The Right Stepped Attenuator For You
Upgrading your volume control is one of the best upgrades you can do to your Hi-Fi. Some would choose an audio-grade potentiometer like an Alps Blue Beauty or one of the range of TKDs. Beyond these, there aren’t too many other options with the demise of the Alps Black, Noble, Penny, and Giles.
A better solution is a stepped attenuator; these work with the principle of a simple voltage divider. A signal derived from a source (CD player or DAC…) enters a resistor network, normally two resistors, at the top of the chain. Depending on the resistor values used, a proportion of the signal is fed from the junction of the resistors to the amplifier. The other end of the chain is earthed, bleeding off the part of the signal that isn't used. These offer better clarity and detail than potentiometers, and if you use a good tolerance resistor of 2% or tighter, you get a fantastic soundstage.
Using a switch and numerous values of resistors at each step, you can create a stepped attenuator to control the volume of your Hi-Fi.
With the fundamentals outlined, you must consider a few things before we go into more detail.
- How many channels do you require? We offer mono (1-channel) for those who want more control over each channel. Stereo (2-channel) is the go-to type. Balanced Stereo for those with balanced systems (XLR inputs and outputs).
- Impedance required - you usually would use the same impedance as the original potentiometer. We offer the choice of 10K, 20K, 50K, 100K and 250K, which covers most values.
- How many steps do you want? We offer various switches that can accommodate 23, 24, 30, 34, 46 and 47 steps. More steps would mean more expenditure but ultimately more control. Most go for 23 or 24. At 2dB between each step, there is plenty of control.
- Space. Stepped attenuators are significantly larger than their potentiometer counterparts, so you need to check they will fit inside your equipment. We provide all the measurements so you can check. Note that if your Hi-Fi uses PCBs, you will have to make flying leads to make the connections to the board.
There are 3 types of stepped attenuators
This type is a long chain of resistors and the switch moves along the chain as the volume shaft is turned. The benefit of the series type is that the overall impedance is maintained throughout the sweep, also, costs are reduced as you only need one wafer of a switch per channel. The downside is that there are many solder joins in the signal path. If you choose a 23-step version, that is, 24 solder joins are part of the signal path, thus the nosier option.
This attenuator is formed by having a constant series/load resistor that the signal passes through initially. How much of that signal passes onto your amplifier depends on the value of the connected shunt resistor. A very economical way to make a stepped attenuator using only one wafer per channel and limited resistors. So, the signal sees only 3 solder joins per step, thus reducing noise. However, be aware that at higher volumes the impedance increases. This type of attenuator is a popular option for these reasons.
This type is created by having two resistors and two switch contacts per step. So, each step is unique. This is sonically the best. It provides a constant impedance over the full sweep. However, it does use twice as many resistors as the other type and requires twice as many wafers to the switch. As a result, it is the most expensive and the largest of all 3 types.
How to choose
Being a component seller, the choice of resistors and switches at our disposal is vast; as a result, there are a lot of options available, which can be confusing.
We have broken our attenuator section of the site into three types: Series, Shunt and Ladder. These are further broken down into how many channels you need: mono, stereo and stereo-balanced. From here, the next choice is switches.
When talking about switches, we refer to poles and ways. To explain, a 1-pole 23-way switch or 1/23 is suitable for a mono series or mono shunt type. Effectively, it has 1 (pole) output that forms an electrical contact with each of the 23 ways (or steps) in turn as you rotate the shaft of the switch.
An important thing to note about the switches is that some of them have exposed contacts, which means that they can become a bit dirty with dust and the like over time and might need cleaning with contact cleaner. The following are such types: 1/23, 2/23 Audio Note NOS (new old stock), 1/23, 2/23, 4/23 Blore Edwards, 1/34, 2/34, 1/46, 2/46 Seiden and 2/30 TKD. It isn’t a big issue, but something to be aware of.
The remaining switches all have covered contacts, namely, 1/23, 2/23, 4/23 Seiden, and 1/24, 2/24, 4/24, 1/47, 2/47 and 4/47 Elma. Popular switches would be the 23-way Seiden and the 24-way Elma type.
Once you have clicked on the switch type, you will see 3 separate attributes to choose from.
- Impedance - at this stage, you should know what impedance you need.
- Supplied as - we are happy to build up your stepped attenuators for a fee. We also supply as a kit. Remember that for a stereo 23-way shunt, there are around 92 solder joins. For the kit, we supply all you need, including the Mundorf 3.8% silver gold solder for construction.
- Resistor type - This is where it gets a bit trickier. You will see in this drop-down box lots of options, starting with the cheapest. If you like a cleaner, detailed sound, then the metal films / Audio Note ranges might be the best for you. However, if you prefer a slightly smoother, natural sound, then the Carbon film type might be the way to go, such as the Takman Carbon or the Amtrans AMRT resistors.
At this point, the series/load resistor of the shunt stepped attenuator range is worth discussing. As you would have read, all the signal passes through this resistor no matter what position you are on. So, this resistor is worth an upgrade. A popular choice here is the Charcroft Z-Foil range. You should add this to your cart. For example, for a Stereo Shunt 50K, you would have to add 2 off the CART 50K000B: 50K 0.4W Charcroft Z-Foil Resistor.
I hope this has helped you in making your choice! There are lots of resources on the site to assist. Including various videos, see below. If you do need any help then please do get in touch.