On Tuesday 27 October 2020 09:33:41 Gene Heskett wrote: Hooked up the 420 watt driver. Can't find any input high pass filter, so I am feeding it a low frequency square wave of up to 80 mv peak to peak. It took a couple hours of diligent net search to find a copy of that chips docs. Apparently the car amplifier folks still think, 5 years after this chip was first shipped, class D is still a proprietary secret. Rated at 33db of gain, an 80 mv signal should drive it halfway to the rails.
AC from a big toroid power tranny is about 53 volts with a grounded center tap, shows about 10 volts per rail less that the 42 volt warning some guy on u-tube claimed. >From the lack of input filter, I get the impression this thing will amplify a dc error. But the output is both low and noisy, and both terminals are in phase. Which makes zero sense. Running its class D at 250 kilohertz, and zero drive, the heat sink sits at 126F and doesn't get a lot warmer with 2 or 3 volts of drive. And while it might make the motor tick occasionally, it doesn't move the motor. Rated to drive speakers down to 2 ohms, 4 preferred, 8 tolerable, this motor is 2.7 ohms stopped. Ought to be right at home. So the results are "puzzling". Previous playing with the 150 watt driver says it can absolutely hammer that motor, but with a single ended supply, it has a high pass filter in its input so it can be driven with ground referenced audio. I'll play some more, and read the 42 page doc I found for clues after I've gotten some more sleep time. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
