Class-d Motherboard and modulators

Class-d Bother Board

Class-d Motherboard

As you have probably seen on my web site, I have been working on class-d amplifiers for some time.

I have succesfully made a 400W full bridge for a subwofer, and a small mini amp based on the UcD design presented by Bruno Putzeys.

I have also for some time been working on a half bridge design, but have not ben so sucessful. Can only tell, it’s not that easy 😉

I have made a couple of models, but all had a bad tendency to be somewhat noisy, having a hissing sound at idle. As the goal is to make something better sounding than my 180 W dual mono LC-Audio The-End, this is of course not acceptable.

I did a trial version with separately regulated supplies for all stages, but it didnt do anything to the noise. Therefore my conclusion is that it is the modulator topology it self that I’m using that is not good enough. Therefore I decided to make a motherboard with all the switching, the filter, the power supply etc. all except the modulator, and a connector where I can place and try out verious modulator designs.

Tried out the new design with a simple SODA modulator, but something is not working as i should. It did start to modulate at some 350 kHz (which is a bit high) but it was not easy to get to start, switching the amp on and of  a lot of times to make it run.

SODA Modulator
SODA Modulator

I was actually a bit nervous that it had burned the whole thing, but then again nothing had become warm or haf smelled ……. To test the motherboard it self, I made up a small oscillator, doing 100 kHz and connected it to the modulator connector. Mother board seems to work just fine, so the fault must be on the modulator.

I will now try to cook up a modulator on a bread board connected to the motherboard.
Stay tuned :)

6 comments to Class-d Motherboard and modulators

  • I want to quote your post in my blog. It can?
    And you et an account on Twitter?

  • admin

    By all means quote my site and make links :)
    Thanks, Baldin

  • You have tested it and writing form your personal experience or you find some information online?

  • admin

    Hi Alton Wright

    It’s my own design. Of course there are a lot from information on the net. Personally I have found lot’s of really good stuff on diyaudio.

    I’m testing it further now. has had quite some troubles making it work with LT1711, and not use these any more. MXL1016 or MAX913 are almost as fast, and has shown to be easier to make work.

    Are working on a mk 2 version of the modulator, SODA with additional post filter feedback, with a few improvements and error corrections.

    Also working on a UcD modulator board.

    I think I’ll end out only testing these two configurations at this point.

    Will post information on results as soon as I have it.

    Best regards Baldin

  • Hi

    are yo going to show the schematics?

  • admin

    Hmmm possibly :)

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