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 Beauties, Noble, Penny and Giles.
A better solution is a stepped attenuator. These are effectively a chain of voltage dividers. A signal derived from a source (e.g. your CD player or DAC…) enters a resistor network, two or more resistors connected in series. The input signal enters the network 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 input of the amplifier. The other end of the chain is earthed, bleeding off the part of the signal that isn't used.
Stepped attenuators offer a better soundstage, clarity, and detail than potentiometers. The better the tolerance of the resistors used, the better the soundstage is.
Using a switch and numerous resistor networks 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. We also offer Balanced Stereo for those with balanced systems (XLR inputs and outputs).
- Impedance required—usually use the same impedance as the original potentiometer. We offer the choice of 10K, 20K, 25K, 50K, 100K, and 250K, which covers most values.
- How many steps do you want? We offer switches that accommodate 23, 24, 30, 34, 46 and 47 steps. More steps would mean more expenditure but ultimately more control. Most customers use the 23 or 24. At 2dB between each step, you have plenty of control.
- Space. Stepped attenuators are significantly larger than their potentiometer counterparts, so you must check that they will fit inside your equipment. We provide all the measurements so you can check. Note that if your Hi-Fi uses PCBs, you must make flying leads to connect to the board.
There are three types of stepped attenuators
SERIES TYPE
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. The cost is reduced as you only need one switch wafer per channel. The downside is that there are many solder joins in the signal path. If you choose a 23-step version, 24 solder joins are part of the signal path, thus the nosier option.
SHUNT TYPE
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. It is a very economical way to make a stepped attenuator, using one wafer per channel and limited resistors. The signal sees only two solder joins per step, thus reducing the noise floor. The downside is that the impedance is not constant over the whole sweep. At higher volumes, the impedance increases. This type of attenuator is the most popular option for these reasons.
LADDER TYPE
This type is created by having two resistors and two switch contacts per step of your switch, so each step is unique. It is sonically superior to the other types. It provides a constant impedance over the full sweep. It has two resistors in each step, but three solder joins. It uses 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 physically of all three types.
HOW TO CHOOSE?
As a component seller, we have a vast selection of resistors and switches, which can be confusing.
We have divided the site's attenuator section into three types: Series, Shunt, and Ladder. Each type is further divided into the number of channels you need: mono, stereo, and stereo-balanced (shunt only). From here, the next choice is what impedance you require and which switches to use. The last decision is which resistor to use.
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 they can become dirty with dust 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 it is 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. The most popular switches are 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. We also offer the more expensive resistor types like the Charcroft and Audio Note silver Tantalums.
SERIES/LOAD RESISTOR FOR SHUNT TYPE
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 your position on your volume dial. 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! The site has lots of resources to assist, including various videos; see below. If you need any help, please do get in touch.