The difference between DSD and class D

[marianneoelund]

Reasons why you can't drive a Class D amplifier output stage directly with a DSD bitstream:
1. Inefficiency. DSD bitstreams do not use the full modulation range due to stability issues with Sigma-Delta modulators; they are generally limited to 50%. Thus a DSD stream would only allow the amplifier to reach 25-30% of its full rated power.
2. Filtering. In spite of Paul's suggestion otherwise, it is *not* simple to filter a 1-bit output down to the audio range, while retaining the full DSD detail and avoiding excessive high-frequency residuals which would overdrive tweeters.
3. No volume control. You cannot alter the signal amplitude in a DSD bitstream using a simple volume control. Achieving volume control requires demodulating DSD to analog or PCM, applying the control gain, then converting back to DSD - all of which would of course completely negate the goal of direct DSD bitstream use. As an alternative, one could modulate the power supply rails, but that gives a rather limited range.
4. DSD bitrate. The lowest DSD bitrate is 2.8224MHz, which would require an output stage capable of operating at a 1.4112MHz switching frequency. Today's designs only operate up to about 500KHz.
5. Distortion. For low distortion/noise, the output voltage levels would need to be *extremely* precise and noise-free; this is not within the capability of current output stage designs and their power supplies. Further, propagation delays and slew rates would need to be balanced to extreme precision and the output filter linearity would need to be nearly perfect, while also being rather complex. Everything needs to work to high precision, without benefit of feedback.

[daemon]

@paul if I'm a transistor looking at a PWM VS PDM Signal how do I notice the difference? (Assuming there is no clock, sync signal)

[kketorasa]

is it posible to use native DSD speakers? 2 poluses where digit 1 magnetically moves it front, 0 back. In that case there no need amplifier and DAC at all, it can be called magnetic field controller. More magnetic field - more volume. Direct DSD Speaker 😊. Is any solutions in 2024?

[alexbusoni]

Why not start combining the amplifier class d and dsd stream without dac converters. To use the output transistors of the d-class amplifier as a converter, because you can amplify the PWM modulated signal directly! For the first time to receive a device - an amplifier d and dac having analog conversion only at the output of power transistors and nowhere else почему бы не начать совмещать усилитель клвсс д и дсд поток без преобразователей dac. что бы использовать в качестве преобразователя выходные транзисторы усилителя д класса, потому что можно усилить шим модулированный сигнал, непосредственно! впервые получить устройство - усилитель д и dac имеющий аналоговое преобразование только на выходе транзисторов мощности и больше нигде

[osirismarbles]

i know this video is 3 years old, but why does it look like it's 30 years old? lol. i feel a maxell tape commercial coming on in 30 secs

[davidtomsett]

I hope Paul does not design his amps on the back of an envelope!

[maaxsxzone]

What about Sharp 1bit SACD player and it's amp. 2 decades back?