When you put a 10 khz square wave into a class D amp , garbage comes out. Square wave tests have been the benchmark of good audio performance. That explains why many concerts bring on listening fatigue. That effect where the sound seems really good at first, but then you want leave after half an hour. Class D is cheap and light weight , that is the entire point of it. I have tested some good class AB designs to full power with 10 khz square wave with clean output. Of course, zobel networks must be disconnected for such testing. The double die lateral mosfet amp in this example is on 10 khz , scope at 20v/div. note the rise time. This could not be done with class D even a fever dream.
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What has a square wave to do with audio??
If you do what every amp tester does, low pass input filtering at say 30kHz when testing with square waves, class D is just as fine as class A or AB.
BTW on your scope pic, your amp is slew rate limiting on the fallng edge. It doesn't do this well, but it is unreasonable to require it anyway so no harm done.
Jan
If you do what every amp tester does, low pass input filtering at say 30kHz when testing with square waves, class D is just as fine as class A or AB.
BTW on your scope pic, your amp is slew rate limiting on the fallng edge. It doesn't do this well, but it is unreasonable to require it anyway so no harm done.
Jan
ah I love it when a class g discussion turns into a religious discussion about class D…’does it sound cold? Well it is called ICE’
Back to class G. I don’t think they got a bad rap but indeed better parts, class D and expense has relegated them to an ‘interesting variant’. I love my hitachi ha-5300, it is getting a full restore soon
Back to class G. I don’t think they got a bad rap but indeed better parts, class D and expense has relegated them to an ‘interesting variant’. I love my hitachi ha-5300, it is getting a full restore soon
They are an interesting variant because class G (H) are completely scaleable, within the limits of available loudspeaker drivers. Class D is still NOT scaleable. A 50 ns difference in propagation delay across a stack of 10 output transistors is a don’t care for class G. It will cause class D to go thermonuclear. The solutions are either to make it electrically small (has practical limits) or lower the switching frequency (impacts fidelity). The switching power supply has the same issues, but lowering the switching frequency below 100kHz is practical. The better ones just run lower frequency as the current demand goes up - and do that to stay in resonant mode. They are not cheap and not available on Aliexpress. You can buy a 3KVA toroid (or two 1.5kVA Anteks) and 22000uF/250V caps for less money. And the intermittent load (one second on five off, for hours) you can put on that without complaint is staggering.
The best super power amps for touring concert use are not class D, but class TD. They are infinitely scaleable, as long as you don’t count on them to put out full power at 20 KHZ (tracking turns off and they run AB and would overheat QUICKLY). For practical frequency/energy distribution they are fine. Tweeter drivers can always use a smaller class D amplifier, running off practical +/-80V supply. Three 200V TO-220’s in parallel (per leg of the bridge) is all that’s needed, and you CAN switch those on and off simultaneously enough, even at 400 kHZ.
The best super power amps for touring concert use are not class D, but class TD. They are infinitely scaleable, as long as you don’t count on them to put out full power at 20 KHZ (tracking turns off and they run AB and would overheat QUICKLY). For practical frequency/energy distribution they are fine. Tweeter drivers can always use a smaller class D amplifier, running off practical +/-80V supply. Three 200V TO-220’s in parallel (per leg of the bridge) is all that’s needed, and you CAN switch those on and off simultaneously enough, even at 400 kHZ.
Three TO-220s in parallel? Infineon has 650 volt GaN parts with 30-odd amps continuous rating / 60ish amps peak, < 0.1 ohm ON resistance, and 10 nanosecond switching time. And they come in P and N flavours:
https://www.mouser.com/datasheet/2/196/Infineon_IGT65R045D2_DataSheet_v01_00_EN-3538345.pdf
https://www.mouser.com/datasheet/2/196/Infineon_IGLT65R045D2_DataSheet_v01_00_EN-3518088.pdf
I'd bet many class-D amps will be GaNified within a few years, especially if Infineon come out with 250 volt parts.
https://www.mouser.com/datasheet/2/196/Infineon_IGT65R045D2_DataSheet_v01_00_EN-3538345.pdf
https://www.mouser.com/datasheet/2/196/Infineon_IGLT65R045D2_DataSheet_v01_00_EN-3518088.pdf
I'd bet many class-D amps will be GaNified within a few years, especially if Infineon come out with 250 volt parts.
I use 4 of these class H 700W @ 8 Ohm modules for my subwoofers, and I've tested them on a set of Magico Q7 too - no problem with audio quality at all, compared to Dan D'agostino mono blocks.
https://groundsound.com/hpa2k.php
Second time was a pair of B&W 800 - the ones with a pair of 10" woofers. These never seemed to sound right - bloated and too "warm". Then with these class H modules, there was suddenly a lot more control in comparison with the Lyngdorf power amp. The owner immediately bought a set and didn't look back.
These modules also seems to "eat" up difficult loads in passive filters and several parallel coupled drivers.
Class D comes closer and closer, but often include fan-noise and coil-whine, if you want high wattage and sensible prices.
Loving these class H modules - they just power anything you throw at them - at any level you wish 😍
https://groundsound.com/hpa2k.php
Second time was a pair of B&W 800 - the ones with a pair of 10" woofers. These never seemed to sound right - bloated and too "warm". Then with these class H modules, there was suddenly a lot more control in comparison with the Lyngdorf power amp. The owner immediately bought a set and didn't look back.
These modules also seems to "eat" up difficult loads in passive filters and several parallel coupled drivers.
Class D comes closer and closer, but often include fan-noise and coil-whine, if you want high wattage and sensible prices.
Loving these class H modules - they just power anything you throw at them - at any level you wish 😍
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54 milliohms of ON resistance, heat sunk through the damn PCB? Thats how class D goes thermonuclear. Move the decimal point one or two places and you get somewhere. That puts you in 200 volt silicon territory. If they were to do a paradigm shift to 600 volt supplies and 16 (maybe 8) ohm subwoofers GaN would be appropriate. Operate in the sweet spot, get the CURRENT down. Probably still want a TO-220 or two, to pull out the 40 watts of heat. Even at 99% efficiency these power levels require heat sinking.