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Crazy idea for a powered sub
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<blockquote data-quote="John Roberts" data-source="post: 48454" data-attributes="member: 126"><p>Re: Crazy idea for a powered sub</p><p></p><p>I am not opposed to DIY... I built my own amp back in the '70s to save money, and because I could. If I needed a new amp today I surely wouldn't do that again (my old amp actually still works). Doing it once was a good experience for me, but i wasn't charging people for sound reinforcement. </p><p></p><p>I am a moderator on a decent sized DIY forum, where I give advice about how to design and make stuff work (even amps)... <a href="http://www.groupdiy.com/index.php" target="_blank">GroupDIY - We break stuff...and occasionally make stuff.</a></p><p></p><p>OTOH for a forum presumably giving advice to people who work providing sound reinforcement, I am inclined to mix in a little business advice. Cobbling together gear that is not likely to work up to professional standards is not the best use of one's time, effort, and money, unless they have aptitude for doing stuff like that, in which case, maybe they should be doing that as a full time job, instead of trying to join the circus. There is a huge different between making some sawdust to DIY speaker cabinets (been there done that too), and re-arranging the innards of power amps. I recently had a similar exchange over on that other (professional sound reinforcement) sound forum about some guy DIY a microphone adapter... For personal use have fun, for business use, use the stock, already engineered solution. </p><p></p><p>I still suspect you underestimate the degree of difficulty to break up and reassemble a digital power amp. I have watched and managed engineers designing them as their day job, when it was their actual area of training and expertise, and it wasn't easy for them. Perhaps if you were planning to tear down an old CS800 and repackage that, I'd make less of a stink, but even in the low tech CS800 a great deal of design effort goes into grounding and thermal management. For example the old CS800 used an unbalanced input so the signal was accepted and passed around single ended. Management of ground currents and noise was difficult to deliver the 100dB or so dynamic range. Since several ground paths include the chassis, every screw matters. </p><p></p><p>Some things about thermal management that may not be readily apparent, it is not a simple matter of just pointing some air flow at a heat sink.. In an optimal design, the amount of cooling airflow delivered to individual devices is managed so the devices reach similar internal temperatures under load. Since some devices are dissipating more or less power, and later devices in the air flow, receive warmer air than the early devices that get cooler air, this is not a trivial engineering feat. If this managed air flow is not replicated precisely, the obvious result is one ore more devices will reach max temperature before the rest of them. If this "hotter" device is on a heat sink with a thermal sensor, it means the amp will probably shut down prematurely before making as much power as a stock design, if the device is not having it's temperature monitored, the device will reach too high of a temperature before the others shut down and likely to fail. Note: Even the heat sink thermal sensor uses only one sensor for multiple devices and will only be accurate if the air flow is properly balanced. </p><p></p><p>I repeat, this is not rocket science, but more complicated than I believe you appreciate. You may be able to get something to work in some fashion, but it will not likely perform near as well as just leaving the amp stock. </p><p></p><p>JR</p><p></p><p>PS If I was going to build an amp today, I like the hypex modules that I think may even be available in kit form. <a href="http://www.hypex.nl/" target="_blank">Convert. Control. Amplify.</a></p></blockquote><p></p>
[QUOTE="John Roberts, post: 48454, member: 126"] Re: Crazy idea for a powered sub I am not opposed to DIY... I built my own amp back in the '70s to save money, and because I could. If I needed a new amp today I surely wouldn't do that again (my old amp actually still works). Doing it once was a good experience for me, but i wasn't charging people for sound reinforcement. I am a moderator on a decent sized DIY forum, where I give advice about how to design and make stuff work (even amps)... [url=http://www.groupdiy.com/index.php]GroupDIY - We break stuff...and occasionally make stuff.[/url] OTOH for a forum presumably giving advice to people who work providing sound reinforcement, I am inclined to mix in a little business advice. Cobbling together gear that is not likely to work up to professional standards is not the best use of one's time, effort, and money, unless they have aptitude for doing stuff like that, in which case, maybe they should be doing that as a full time job, instead of trying to join the circus. There is a huge different between making some sawdust to DIY speaker cabinets (been there done that too), and re-arranging the innards of power amps. I recently had a similar exchange over on that other (professional sound reinforcement) sound forum about some guy DIY a microphone adapter... For personal use have fun, for business use, use the stock, already engineered solution. I still suspect you underestimate the degree of difficulty to break up and reassemble a digital power amp. I have watched and managed engineers designing them as their day job, when it was their actual area of training and expertise, and it wasn't easy for them. Perhaps if you were planning to tear down an old CS800 and repackage that, I'd make less of a stink, but even in the low tech CS800 a great deal of design effort goes into grounding and thermal management. For example the old CS800 used an unbalanced input so the signal was accepted and passed around single ended. Management of ground currents and noise was difficult to deliver the 100dB or so dynamic range. Since several ground paths include the chassis, every screw matters. Some things about thermal management that may not be readily apparent, it is not a simple matter of just pointing some air flow at a heat sink.. In an optimal design, the amount of cooling airflow delivered to individual devices is managed so the devices reach similar internal temperatures under load. Since some devices are dissipating more or less power, and later devices in the air flow, receive warmer air than the early devices that get cooler air, this is not a trivial engineering feat. If this managed air flow is not replicated precisely, the obvious result is one ore more devices will reach max temperature before the rest of them. If this "hotter" device is on a heat sink with a thermal sensor, it means the amp will probably shut down prematurely before making as much power as a stock design, if the device is not having it's temperature monitored, the device will reach too high of a temperature before the others shut down and likely to fail. Note: Even the heat sink thermal sensor uses only one sensor for multiple devices and will only be accurate if the air flow is properly balanced. I repeat, this is not rocket science, but more complicated than I believe you appreciate. You may be able to get something to work in some fashion, but it will not likely perform near as well as just leaving the amp stock. JR PS If I was going to build an amp today, I like the hypex modules that I think may even be available in kit form. [url=http://www.hypex.nl/]Convert. Control. Amplify.[/url] [/QUOTE]
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