Im once again working on a class d, i´d revisiting the sigma delta class d that at first try failed.
This is the one i tried building but failed: http://ece.wpi.edu/analog/mqps/ClassD_MQP_Final.pdf
Now i built this: http://diymania.hv4all.com/sigma delta modulator/sigmadeltamodulator.PNG and it works nicely, apart from a slight beep, which i blame on a crappy layout on a breadboard with no bypass caps what so ever on the rails.
It runs off a TL074, a 74HC74 with a 8MHz clock and uses a TC4422 as output device. The output filter is yet a dc choke, gonna wind a proper choke later on.
What do you think, worth to continue to work on ? It does sound very good for what it is.
This is the one i tried building but failed: http://ece.wpi.edu/analog/mqps/ClassD_MQP_Final.pdf
Now i built this: http://diymania.hv4all.com/sigma delta modulator/sigmadeltamodulator.PNG and it works nicely, apart from a slight beep, which i blame on a crappy layout on a breadboard with no bypass caps what so ever on the rails.
It runs off a TL074, a 74HC74 with a 8MHz clock and uses a TC4422 as output device. The output filter is yet a dc choke, gonna wind a proper choke later on.
What do you think, worth to continue to work on ? It does sound very good for what it is.
Now i have improved this thing quite a bit.
Only background nice that is hearable now is a faint hum that i dunno where it comes from since this thing runs off a smps.
Sound is very good for beeing a quick lashup on a breadboard
It looks like this: http://diymania.hv4all.com/sigma delta modulator/sdamp.wmv
Only background nice that is hearable now is a faint hum that i dunno where it comes from since this thing runs off a smps.
Sound is very good for beeing a quick lashup on a breadboard
It looks like this: http://diymania.hv4all.com/sigma delta modulator/sdamp.wmv
Lars Clausen said:Tekko: Drop the 1 bit quantiziser, it will only increase quantization noise. Simply short it out, then you are in better shape.
I did as you suggested, modeling it with LTSpice. In fact I left out the quantizer and the power driver. Sure enough, it works. Is that all there is to a self-oscillating Class-D?
What determines the modulation frequency?
This amp is now stereo and sounding good, but since its a breadboard, the channels interfer with each other = hissing.
Nope i dident drop the quantizer. Removing it would make this a standard self oscillating pwm amp, not delta sigma as it is now.
Im ny case the TL074 limits freq to 2MHz, should be 4MHz, clock is 8MHz as stated before.
Nope i dident drop the quantizer. Removing it would make this a standard self oscillating pwm amp, not delta sigma as it is now.
Im ny case the TL074 limits freq to 2MHz, should be 4MHz, clock is 8MHz as stated before.
Why did you try to run it at 8 mhz? You will never be able to drive power stage at that frequency...I already use this topology in my HVI serie amplifier, but take low frequency feedback at the output and hight frequency feedback before the coil...Work very weel at 500 Khz...
Fredos
Fredos
Hey fredos!
Well the 8MHz xtal module was all i had, i also had a 2MHz xtal module but that one was broken, no output.
Yes i know i cannot run a real output stage at these frequencies, but i can use another 74HC74 to lower the frequency of the master clock to a lower frequency.
Well the 8MHz xtal module was all i had, i also had a 2MHz xtal module but that one was broken, no output.
Yes i know i cannot run a real output stage at these frequencies, but i can use another 74HC74 to lower the frequency of the master clock to a lower frequency.
Heres a schemo of a new design i´ve whipped together.
http://diymania.hv4all.com/selfosc classd/D-Amp2.png <-- will it work with the level shifters and that stuff ?
http://diymania.hv4all.com/selfosc classd/D-Amp2.png <-- will it work with the level shifters and that stuff ?
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