To further minimalize any degradation of the audio signal, I'm interested in learning about a full PWM system.
My goals are:
Reduce amount of conversions in a system with a digital source
Learn about the practical application of such systems
Learn about the existence of chip amps that allow PWM input
Learn about issues regarding the interconnectivity of PWM based devices, clock synchronization, signal voltages and such
In the end, produce an ecosystem of PWM connected devices.
The end goal:
Have a sound system which can use HDMI signal as input, do surround processing for home theatre purposes, do speaker management (DSP), and amplify the signal and then be used for the speakers.
The final system would consist of the following devices:
- HDMI signal source
- Digital receiver for dolby (etc.) decoding, splitting into seperate outputs per speaker channel
- DSP's for speaker crossover and time alignment
- Amplifiers to drive every speaker unit seperately.
The HDMI signal source could be anything, ranging from laptop, phone, cable box, desktop computer etc
The digital receiver will need to be able to switch between sources, have advanced controls for selecting small/large speakers and subwoofer control.
Also, it will need to be modified, so that the DAC's are bypassed. Therefore it will need to have seperate DACs, or at least seperate PWM signal paths to each speaker.
The DSP will need to have advanced crossover controls and will need to be modified, so that the input ADCs, and output DACs are bypassed.
The speakers are going to be 5-way, so at least 5 output channels are needed for each speaker. The Behringer DCX2496 seems to be a good candidate. It is possible to modify the unit into accepting and outputting PWM. Because the number of outputs is limited to 6, and the (5) speakers are going to be 5-way, it is natural that for a 5.1 system, at least 5 DSPs are needed. One for each speaker, so that at least 5-channel playback is possible.
The amplifier will need to have a PWM input.
Before going the full-PWM way, I was heavily leaning towards using IRS2092 amplifier boards for amplification. However, since this chip has a built-in PWM modulator, it is not suitable for PWM input. It's brother, the IRS20957S has no internal PWM modulator, so it looks like it will be suitable for this build. A low pass filter demodulates the signal after being amplified.
The audio signal will follow this path approximately:
HDMI>Receiver>DSP>Amplifier>Speaker
Notes
I do realize that most sources provide a PCM Signal, but the difference this system makes is that the PCM signal will only be decoded once, in the 'Receiver' part, into PWM, and then stays that way until after the power amplifier.
Questions
1: Have you ever heard of such a system already in existence?
2: Have you heard of a PWM audio signal beïng transferred between two seperate devices, or know about problems that could be introduced by this?
3: Do you know about this PWM signal to be different in voltage between two devices?
Further, any elaboration on this subject that could be of use to my experiment is very welcome.
Thanks for your time
My goals are:
Reduce amount of conversions in a system with a digital source
Learn about the practical application of such systems
Learn about the existence of chip amps that allow PWM input
Learn about issues regarding the interconnectivity of PWM based devices, clock synchronization, signal voltages and such
In the end, produce an ecosystem of PWM connected devices.
The end goal:
Have a sound system which can use HDMI signal as input, do surround processing for home theatre purposes, do speaker management (DSP), and amplify the signal and then be used for the speakers.
The final system would consist of the following devices:
- HDMI signal source
- Digital receiver for dolby (etc.) decoding, splitting into seperate outputs per speaker channel
- DSP's for speaker crossover and time alignment
- Amplifiers to drive every speaker unit seperately.
The HDMI signal source could be anything, ranging from laptop, phone, cable box, desktop computer etc
The digital receiver will need to be able to switch between sources, have advanced controls for selecting small/large speakers and subwoofer control.
Also, it will need to be modified, so that the DAC's are bypassed. Therefore it will need to have seperate DACs, or at least seperate PWM signal paths to each speaker.
The DSP will need to have advanced crossover controls and will need to be modified, so that the input ADCs, and output DACs are bypassed.
The speakers are going to be 5-way, so at least 5 output channels are needed for each speaker. The Behringer DCX2496 seems to be a good candidate. It is possible to modify the unit into accepting and outputting PWM. Because the number of outputs is limited to 6, and the (5) speakers are going to be 5-way, it is natural that for a 5.1 system, at least 5 DSPs are needed. One for each speaker, so that at least 5-channel playback is possible.
The amplifier will need to have a PWM input.
Before going the full-PWM way, I was heavily leaning towards using IRS2092 amplifier boards for amplification. However, since this chip has a built-in PWM modulator, it is not suitable for PWM input. It's brother, the IRS20957S has no internal PWM modulator, so it looks like it will be suitable for this build. A low pass filter demodulates the signal after being amplified.
The audio signal will follow this path approximately:
HDMI>Receiver>DSP>Amplifier>Speaker
Notes
I do realize that most sources provide a PCM Signal, but the difference this system makes is that the PCM signal will only be decoded once, in the 'Receiver' part, into PWM, and then stays that way until after the power amplifier.
Questions
1: Have you ever heard of such a system already in existence?
2: Have you heard of a PWM audio signal beïng transferred between two seperate devices, or know about problems that could be introduced by this?
3: Do you know about this PWM signal to be different in voltage between two devices?
Further, any elaboration on this subject that could be of use to my experiment is very welcome.
Thanks for your time
Axign | Digital Feedback Loops offer a solution (http://axign.nl/wp-content/uploads/AX5689_amplifier_controller_product_brief_D2g.pdf) of feeding a class-D output stage directly with a PWM signal from a digital PCM input. But they use (fast!) ADC to close a digital (PCM-domain) feedback loop around it so it has good specs, so it might not fit your goal of little to no conversions (which is a misguided goal im my view).
Last edited:
It's no more or no less from an ordinary 3 box setup like: Source -> DAC -> PWM amp. Same number of PCM decoding stages.. =1.
But your short analogue signal paths may be an advantage! I believe it's the right way to go.
//
A PWM output will always need a feedback to the modulator to work properly with a speaker load and other sources of error (supply etc). So either you go standard way with using an analog modulator feed from a DAC or you need an ADC to get the output sense signal (no matter if in front of or after a LC filter) back into PCM for processing in digital domain.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.