A Feature-Rich Amplifier Module For 3-Way Speaker Builds

There’s something rewarding about building your own DIY audio hardware. Knowing you put it together yourself gives you faith in the construction, and psychosomatically makes the music sound all that much sweeter. If you’re into that kind of thing, you might like to give [Eric Sorensen’s] Denmark amplifier module a look.

The amplifier is intended to be used in a 3-way system, running a subwoofer, woofer, and tweeter. It uses a 1000 W ICEpower module to run the subwoofer, with a pair of 500W ICEpower modules to run the woofer and tweeter respectively. Meanwhile, a MiniDSP 2x4HD is used to accept optical audio input. It also offers digital signal processing and serves as a crossover to split the signal across the three speakers. An STM32F401 is used to run the show, controlling all the various modules and the necessary status LEDs. It’s a feature-rich build, too, with overtemperature monitoring, fan control, and clipping warnings built in.

The whole setup is built on to a sturdy aluminium backplate. The CNC-machined panel has simple tactile buttons for control. There’s also a nifty use of clear PETG 3D printer filament as a light pipe for LEDs. It’s effective, and it looks great. The whole module is designed to slide into the bottom of a 3-way speaker housing like a drawer.

Overall, if you’re building a big set of 3-way speakers, you might find the Denmark amplifier module is perfect for your needs. Alternatively, you could experiment with a different kind of speaker entirely. Video after the break.

22 thoughts on “A Feature-Rich Amplifier Module For 3-Way Speaker Builds

    1. ICEpower claim 1100 watts into 4 ohms at 1% THD. The 0.1% THD value will likely be much lower. They don’t state whether this is RMS watts or something else. I doubt it will be PMPO though as this measurement is thankfully not used so much anymore.

      1. Yeah. If it doesn’t mention RMS I get suspicious. My cell phone speaker can put out a kilowatt if you measured it for one picosecond as I throw it into a brick wall. I’m sure it’s just an omission

      2. For an ‘educated’ audience there is sure a lot of incorrect speculation. If you look at the data sheet, frequency dependant it is 0,1% THD for the majority of the audio bandwidth up to 1kW.

        No-one has quoted ‘PMPO’ for years, definitely not respected companies such as ICEpower.

        But hey, why not guess.

        1. What? I can find you lot’s of peak power speced audio gear, just search Amazon for audio…the PMPO ETLA has fallen from use. But same as it’s ever been, if it’s not explicitly stated as RMS, it’s peak.

          There’s two new generations of chumps out there and they are super, super chumpy. Have you been paying attention lately?

          All the old lies are back. There are kids that want very average audio brands (e.g. Sansui) because someone found their old THD lies. Pubished THD #’s at -50Db vs most other brands doing it at rated power.

          I’ve seen kids arguing over which Matsushita label made the best amps or cassette tape decks (Pioneer!, No Akai!). What do you expect from morons that use cassette tape or LP in 2023?

          Which isn’t to say there is no good old gear. There is very little new in the audio amp world. Switching power supplies and very cheap Alibaba tube amps. You can still roughly tell the quality of an audio amp by curling it. Weight good. Just compare apples to apples. Swiithching power supplies are much lighter.

          I’d love a nice old set of electrostatic speakers.

          WTF does ‘0.1 THD for the majority of the audio bandwidth’ even mean? That you can finagle the number down by redefining audio range to suite the data…duh.

          1. I think it’s great to be skeptical. Especially in the audio world.

            That said the 1000ASP and especially some of the newer class D modules are pretty impressive (Hypex especially).

            Have you checked out the data sheet for the 1000ASP?

    1. 500W is more than necessary and I will never drive them that high. The speakers are using compressor tweeters rated at 180W continuous and 240W peak power handling.

      The advantage of using 1000W + 500W + 500W is that this also works well as a 2.1 stereo amplifier with just some DSP coefficient changes. 500W per speaker and 1000W for the amplifier. And it almost never hurts to have extra headroom. :)

    2. It’s not always as excessive as you may think. I suggest you look up crest factors to understand music signals in relation to sine waves. Always operating in the ultra low THD section of the amplifier yields sonic benefits, as well as a comfortable operating margin for the amplifier electronics, yielding reliability benefits.

  1. Running line level signals to each speaker via shielded coax cable is asking for noise pickup, especially if the cables are long. I think I would make an unbalanced to balanced converter for the source and run balanced lines to the speakers.

    1. Not disagreeing with you but I don’t see any RCA jacks and the article mentions the “optical digital input”, so I think he’s covered it. That said, is TOSLink used any more ?

    2. The noise rejection in a balanced audio system occurs at the input. A balanced impedance source is needed for optimal performance of a proper balanced input but, Eric doesn’t appear to have a balanced, analog input so there’s no point to a balanced output at the source.

  2. The short story here is in not the power amp but the architecture of what makes up today’s “stereo”, say a file with VLC playing it the stream will arrive at the power amp-speaker through it’s 32 bit path with volume control at this point. Already great enough the DSP box is where a rack of gear would be. With an adaptive mic test of the room this qualifies as a smart speaker not those beer can listening devices.

  3. I’m guessing the F401 is in use for something so simple because a Nucleo board or blue pill is what was on hand to prototype. Either that or someone just decided ‘F Arduino! I’ll use MBed!’

    1. Pretty much.

      I have a bunch of those Nucleo boards and I use the F401 for a lot of my projects. I already have the PCB footprint tested and I’ve setup this chip many times so I can start developing quickly. I am building two of these total — my time is a lot more valuable than saving a few dollars when I am only building two of these.

      I don’t use MBED, but I do use use the STM32Cube tool for a lot of the setup — including FreeRTOS.

  4. Made my own analog class b amp few years ago.

    2 big transformers

    2 bridge rectifier
    2 0.5f capacitors
    4 transistors and
    4 op amps in 2 packages

    Also no filters in the audio Path so it can be used as a stepper driver or even a variable voltage supply

    Wooden box around it

    No volume knob no noting

    Also no hum wat so ever

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