New & Reviewed

Spotlight On: DIY DSP

Daniel Koch

Issue 40, November 2020

High-Quality Digital Sound Processing in a project-level format from Dayton Audio.

Digital Sound Processing (DSP) is something many of us would immediately think of as a production or studio task, and probably too complex for home use. However, it is something that can benefit any high-quality audio system. In analog days, many will remember using equalisers, which may have been a set of dials or a row of slider potentiometers which could adjust low, low-mid, mid-range, high-mid, and high frequencies. Some home systems even had 15-band equalisers.

In the transition to digital, often only basic software control was provided to adjust sound. Digital systems were marketed as far superior and not in need of such user control.

The reality was different, however. Most home theatre amplifiers now have much more control buried somewhere in a sub-menu.

That doesn’t do much for people who still want to build their own customised audio systems. We are seeing a resurgence of high-quality components from amplifiers to speaker drivers available on the retail market.

That’s where DSP comes in. DSP add-ons handle the job of signal conditioning with far more capability than was possible with manual equalisers. In addition, they can usually be plugged in to a computer for ultimate control.

Enter Dayton Audio, distributed by Wagner Online. We have a trio of DSP partnered items to look at, which can be added onto Dayton Audio amplifiers or used inline with the input to other systems. The components of the set are complimentary, so we’ll look at all three, but they could be used on their own if your needs are such.


The modules we’re reviewing are part of the bigger Dayton Audio system. It consists of signal processors, programmers, and a range of digital amplifiers which can be configured as active crossovers.

A traditional audio system consists of an amplifier which has, for a stereo system, a left and right channel. Some have a third channel for a subwoofer, or more for surround speakers. In any case, the amplified signal is fed to the speakers, which contain within their enclosures a network of inductors and capacitors so that the correct frequencies are sent to the tweeter, midrange, and woofer drivers of the speaker. This system has served for many years and still does.

However, with the Dayton Audio digital system, the amplifier boards can be programmed. Instead of crossovers, the enclosures have the amplifier boards mounted into them.

A 2 x 15W board, for example, would not be used as a stereo amplifier, but programmed so that one channel feeds certain frequencies to the tweeter, and one to the midrange or woofer. There are mono modules that can be added to give a third channel, so that a tweeter/midrange/woofer 3-way speaker can be constructed.

Battery power is an option for most of the range and Bluetooth is possible on some items as well. The programming can be done in a basic form by an app, or with the full range of options in Analog Devices’ SigmaStudio program.

The Full Kit:

The items we received from Wagner Online are part of this system, but the Kernel Board and its Expansion Board can be used to provide DSP with a regular RCA (or 3.5mm) in/out arrangement, to a standard stereo signal. This means you can get the benefits of DSP and Sigma Studio on any amplifier, albeit without some of the possibilities of having the programmable amplifiers. The In-Circuit Programmer (ICP) works with these kits but is also used to program the amplifier boards.


The word Kernel is well-known to many familiar with computers and coding, but its basic meaning is ‘basis’ or ‘centre of’. It’s also the soft part of a seed or nut, but if those are in your audio project, you have serious problems, and probably an ant nest.

The DSPB-K Kernel Board is the heart of this DSP set-up. It is based around Analog Devices’ ADAU1701 audio processor, a popular and well-respected IC. This does most of the work, leaving the rest of the board populated by a few discrete components, some headers, and four trimpots.

The former provide connection to the ICP, Expansion Board (or amplifiers) and two 20-pin header ‘control ports’. The documentation does not go into any further detail about these, there are no connectors the same style on any other board, and there are no adaptor cables in the range. They do, however, have pinout labels underneath. The trimpots provide subwoofer gain, subwoofer low pass adjustment, stereo high pass adjustment, and stereo gain.

The kernel board can be used without programming if these controls are all you need. However, it’s likely that you’ll want far more. There is a USB Micro-B socket on the board, but this is for power only. Programming is only possible by the ICP. There is a reset switch onboard should things hang or lock up, so you won’t necessarily have to connect the ICP when things go wrong.


The DSPB-KE 2-in 3-Out Kernel Expansion Board links to the kernel Board exclusively and provides inputs and outputs, but adds specific functionality as well. It consists of three headers, five RCA sockets, and two 3.5mm stereo sockets. One of the headers connects the Expansion Board to the kernel Board, while the other two are smaller and are break-outs for the same signals as the RCA and 3.5mm sockets.

Two RCAs are for Audio In Left and Right, two are for Out Left and Right, and one is for Subwoofer out. The 3.5mm sockets are for Audio In and Out. In its most basic functioning form, the Kernel and Expansion Board can function as a signal processor to take a subwoofer signal to a separate amplifier from a regular stereo source.

However, there are far more possibilities. After being appropriately programmed with the ICP and SigmaStudio, the combination of Kernel and Expansion Board can condition the passing stereo signal in any way that you can program it.

You might take out one resonant frequency that causes problems in a specific space. You might lift the bass or emphasise a range of midrange frequencies but not others, perhaps to compensate for lackluster sound processing in an otherwise impressive TV. The documentation also gives examples of how to use the combination to yield a three-way output signal - woofer, midrange, and tweeter - for separate amplification as an active crossover.

Left: Kernel Board, Centre: Expansion Board, Right: ICP Board

On the subject of documentation, we were only able to find one manual for the whole range of products and not an individual one for the items in question, which didn’t help in trying to solve the above mystery of the ‘control ports’.

The Expansion Board comes with a short 10-pin header cable for connecting the two boards, as well as four standoffs and eight cap screws to mount the two boards together in a very neat package. The Expansion Board is powered from the Kernel Board and cannot be powered on its own. Not that there would ever be a need to anyway.

There is a separate expansion cable pack available as a generic item that suits several products. It contains three terminated LEDs for use with the amplifier boards, as well as three-, four-, and six-pin header cables. This is the only source we can see of a cable that could be used with the Audio In/Out headers on the Expansion Board.


The In-Circuit Programmer is the heart of the range. This device connects to a computer via USB, but also has a Bluetooth module built in to connect to the phone app. It functions as a translator to convert the graphic, drag-and-drop style functions of the software, into language the audio processors can use.

The ICP plugs into boards via a six-pin header, and can connect to the Kernel Board as well as the range of DSPB and KAB amplifier boards. This part of the system is the true heart of the whole range, as without it, and the supporting software, the range is just a bunch of fancy amplifiers.

With it, they are powerful audio tools. All of the amplifiers can be programmed with their own crossover and cut-off characteristics among a myriad of other parameters, and the ICP is the tool that does this.

The ICP has the same footprint as the Kernel and Expansion Boards, so it could conceivably be mounted to them, but the standoffs for that are not in the range. You would need to source some M3 bolt-to-socket standoffs for that. However, you will rarely want the ICP anchored to a project, so it’s really redundant. You would more likely be designing a custom 3D printed enclosure and mounting it in there.

Because SigmaStudio is a third-party product, we’re not reviewing it here. That has been done and the results can be found easily enough. Or, because it’s free, you can download it and play with it. Or can you? Dayton Audio’s DSP Control app is available for Android and Apple phones, but the computer software? Gone are the days when Mac was for graphics and media people, and all serious work was done on PC.

Today, a great many computers today are running Mac OS software even if they are PC-based architecture. They are permeating even the traditional industrial and commercial territories owned by Linux-based PCs. Yet SigmaStudio, distributed by Analog devices, is available for PC only. Why?

The answer lies in the fact that it is built on Microsoft’s Dot Net framework. This was likely a good and efficient design decision at the time, but times change fast and the Dot Net framework cannot be easily ported to Linux or Mac. This means that to support these platforms, Analog Devices will have to start from scratch, and that’s a very expensive, time-consuming exercise that will no doubt be dictated by sales volumes and demand.


The Kernel and Expansion Boards are a versatile tool to adapt to many situation-specific audio circumstances and needs.They are very well built and presented, and quite user-friendly.

While the concept of active crossover has adherents and detractors, the signal conditioning aspects of the system are very useful, especially among modern consumer amplifiers which make so many assumptions and offer little customisation.

If you do want to control or enhance the sound in an existing amplifier and if you’re not an audio engineer (or even if you are), or need a subwoofer output where there is currently none, then the Dayton Audio range from Wagner Online is very worthwhile.

We'll definitely be using these in a future project. Very high quality kit with some amazing potential.

Shopping List

All parts are available at Wagner Online:

  • Kernel Board DSPB-K $39.95
  • Kernel Expansion Board DSPB-KE $19.95
  • In-Circuit USB and Bluetooth Programmer DSPB-ICP1 $49.50