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Diy d-class amp, cooling question

Discussion in 'Amps and Cabs [BG]' started by Matthijs, Aug 13, 2019.


  1. Matthijs

    Matthijs

    Jul 3, 2006
    Amsterdam
    I’m putting together a 400w poweramp, built with a Hypex amp and a Smps module. It’s meant as a power amp to compliment my Pf-20t.

    The plan is to fit it in a solid aluminium housing that will also act as a cooling body for the amp module. I’m confident this will work for the amp, but unsure about the power supply. The supply depends on the air to cool it and the housing will be closed. It is a bit overspec for the amp and does not seem to be very sensitive to overheating. On the other hand it will be easy to create some vents or even install a fan. I kind of like the ‘beerproof’ specs of the housing, but can live without them.

    Does anybody have any experience with smps and DIY in this aspect? Do I need to add a fan to the partslist or is it safe to first wait and see how hot it gets? I bought most parts on the cheap except for the smps, so it would be a shame if thats the part that will fail on me.
     
  2. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    It's a whole lot more complicated than that. How does the heat get out of the components themselves.

    You are asking a question that has an answer that depends on many factors. I might spend a hundred hours on thermal design, profiling and testing. There's no 5 minute answer imo.
     
    equill, Bflat, Dabndug and 2 others like this.
  3. Matthijs

    Matthijs

    Jul 3, 2006
    Amsterdam
    I’m doing this as a fun DIY project and am not expecting absolute garanties on reliability. But I’ll take your reply as a justified warning.

    The manufacturer of the smps module only prescribes a certain amount of room around the module. The module itself has two smallish cooling bodies on It. The proper way would be to create some vents and allow room for air to flow, the manufacturers information does not specify anymore.
    I was just wondering, as the supply is designed to feed two of these amp modules and I’m only using one, maybe I can take the risk to keep the housing closed. But as you rightly pointed out maybe that’s no decision for a hack like me to make just like that. I’ll make some holes in the housing.

    I guess I was just hoping for somebody on the internet to tell me it’s allright
     
  4. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Thermocouples on key parts and extensive testing is how to know for sure. Otherwise it's just a guess, your guess will be every bit as good as mine I suppose.

    Your experience highlights why successful commercial implementations of SMPS/class D products depend so much on analysis and testing. Every aspect of the design and packaging has an impact on thermal performance, plus thermal performance may also influence other aspects of electrical performance. It's highly interdependent.

    Commercial products are not immune to a characterization of thermal and electrical design... there have been some glaring "poor guesses" in commercial products, some of which helped fuel early prejudices against the technology.
     
    Dabndug, Balog, mmon77 and 1 other person like this.
  5. Matthijs

    Matthijs

    Jul 3, 2006
    Amsterdam
    Best to make my guesses on the safe side then .
     
  6. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    That's always been my thoughts but I have a whole community to answer to if I'm wrong ;)
     
  7. It is a big deal to do right as you heard Agedhorse says he "might spend a hundred hours on thermal design, profiling and testing."
    Also Mr. Genzler has said that when designing the Genzler Magellan amps they spent more time on the cooling than other aspects of the designing process, and he spent a lot of time on all aspects of those amps for reliability and performance that shows that cooling is very important.


    I do not know the answer to this but it will require understanding airflow a bit more than just making some holes.
     
  8. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    What model SMPS is it, exactly? Stagnant air is a pretty bad cooling medium. [​IMG]
     
  9. Matthijs

    Matthijs

    Jul 3, 2006
    Amsterdam
    It’s a hypex smps400a400 the matching power supply to a 400ecd oem amplifier module. Both units are widely used in powered speakers.

    Consider me already talked out of the stagnant air method. But as the datasheet does not specify much more on airflow. I think it should be enough to make sure air can flow and not be to skimpy on the holes.
     
  10. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    OK, I suggest you download this for starters: https://www.hypex.nl/img/upload/doc/an_wp/AN_Thermal_design.zip
     
    kesslari and mmon77 like this.
  11. Matthijs

    Matthijs

    Jul 3, 2006
    Amsterdam
    Thanks, that’s an interesting read. I guess I have some homework to do.

    I was planning to quickly some design elements from other amps using the same module and overspec when in doubt. But if I’m challenged with the proper way .....
     
    Bill Whitehurst and Passinwind like this.
  12. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Yep, doing your homework pretty much always pays off.

    When I did my first modern era DIY amp build I had a very expensive commercial piece on hand that used the same series ICE module, but at a higher power rating, and I took a really good look at how they had done it. I found a number of hi-fi implementations too, and then I just threw a dart and figured I could always add a fan if I had to, although I greatly prefer simple convection cooling for my own practice, jamming, and gigging situations. That amp's never given me a lick of trouble, and it's had plenty of chances to do so. My next builds used a newer module and I had no commerical solutions to guide my way at that time. So I did the math and then did open air testing, and roughly doubled what that told me to do. The heat sinks are heavier than the power module, but again, no problems over multiple years of use. I made the venting so it could be doubled up if any problems showed themselves, just because painting yourself into a corner kind of sucks.

    Best of luck, amd please post a build thread if you're up for that.
     
    Last edited: Aug 13, 2019
  13. Matthijs

    Matthijs

    Jul 3, 2006
    Amsterdam
    Thanks. I’ll try to do a build thread.
     
    Passinwind likes this.
  14. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    If nothing else, it will give you a better appreciation for the effort and detail that goes into a stable commercial design. Imagine the risk of having thousands of amps that "missed the mark".
     
  15. Matthijs

    Matthijs

    Jul 3, 2006
    Amsterdam
    I’m in appreciation already

    But for now theres a Ajax Champions Leage game that needs to be watched.
     
    agedhorse likes this.
  16. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    I don't have to imagine, I've seen it in a factory environment where cleaning up the mess was job one and mostly why I got hired in a very rare off-the-street fashion. Not a great way to start a "dream job." [​IMG]
     
    agedhorse likes this.
  17. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    The greater the numbers, the bigger the mess!
     
    Passinwind likes this.
  18. I agree with your idea of finding out how they are cooled in the powered speakers.
    If in doubt, an extra fan can only hurt noise and expense.
     
  19. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    If the airflow is not correct it can also hurt reliability. On some of the better SMPS and amp designs there are a host of thermal sensors that track specific operational parameters which can be adversely affected by improper air flow.
     
  20. +1
    I was often an outside rescuer. I appreciate being retired, no longer fielding the crisis calls from noncustomers. Usually they simply needed to go back in time.
     

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