Hi All,
I have started this thread to post circuits and block diagrams for this project.
This what I am thinking the amplifier layout will look like, the size of case will be base the size circuit boards.
The Power LDMOS Transistors I thinking of using are the MRF101AN and the MRF101BN made by NXP, therefore the cost to start with will be high as device are somewhat expensive. But it is possible to run them at 10 MHz switching speed, making it possible to pass through DSD 64 and DSD 128 without conversion.
Tested basic PDM ADC, using a 74HC74 D type flip flop, I will need to improve its performance by adding in a negative feedback loop.
As you can see there is nothing to it, as for the 1.8432 MHz oscillator goes, it was what I had available to use at the time to provide the clock signal.
Wave forms:
This is a project that will take some time to develop as there a lot more to workout before I even start to think about a PCB
I have started this thread to post circuits and block diagrams for this project.
This what I am thinking the amplifier layout will look like, the size of case will be base the size circuit boards.
The Power LDMOS Transistors I thinking of using are the MRF101AN and the MRF101BN made by NXP, therefore the cost to start with will be high as device are somewhat expensive. But it is possible to run them at 10 MHz switching speed, making it possible to pass through DSD 64 and DSD 128 without conversion.
Tested basic PDM ADC, using a 74HC74 D type flip flop, I will need to improve its performance by adding in a negative feedback loop.
As you can see there is nothing to it, as for the 1.8432 MHz oscillator goes, it was what I had available to use at the time to provide the clock signal.
Wave forms:
- is the PDM Q output from the Flip Flop
- is the Clock input
- is the sine wave from the output of the low pass filter
- Is the 4 kHz input sine wave from the signal generator
This is a project that will take some time to develop as there a lot more to workout before I even start to think about a PCB
Interesting, subscribed. Will it be a project members can join?! With PCB's or Berber's available?
It may be handy to use the more familiar terms PowerDAC or FDA (Full Digital Amplifier). Experiences with FDA having analog inputs and therefor ADC's to be able to connect old analog stuff has been disappointing till now, all devices performed way better when the digital inputs were used regardless of the quality of the used ADC. One thinks of old analog sources with passion...till they are connected in a modern chain 🙂 Since most sources are digital focussing on the digital inputs also seems the shortest path from A to B as it saves 2 conversions.
It may be handy to use the more familiar terms PowerDAC or FDA (Full Digital Amplifier). Experiences with FDA having analog inputs and therefor ADC's to be able to connect old analog stuff has been disappointing till now, all devices performed way better when the digital inputs were used regardless of the quality of the used ADC. One thinks of old analog sources with passion...till they are connected in a modern chain 🙂 Since most sources are digital focussing on the digital inputs also seems the shortest path from A to B as it saves 2 conversions.
Last edited:
If you like "members can join", as for the name you can call it what you like? I will leave it open to the members.
As ADC 1 and ADC 2, again it is up to you on which ones you would like to use, or direct in for digital.
*Note - there is so much more work to done, as this is only a basic idea at this stage.
As ADC 1 and ADC 2, again it is up to you on which ones you would like to use, or direct in for digital.
*Note - there is so much more work to done, as this is only a basic idea at this stage.
Join as in "collaborate/have influence" and "obtain PCBs".
What's in a name one would say. I know it does make a difference after having named a few devices with non sexy names or technical names. "DAC switching amplifier" is a too common name but only take this as well meant advice.
What's in a name one would say. I know it does make a difference after having named a few devices with non sexy names or technical names. "DAC switching amplifier" is a too common name but only take this as well meant advice.
Hi Grantwt, a question, does your DAC switching amplifier use some kind of error correction, or do you mean that the distortion is sufficiently low without any correction when converting the digital signal to analog output in your amplifier?
I would expect some form of distortion with the PCM to PWM conversion and like wise PDM to PWM process, how much I will not know until I build the prototype, as the way I am doing this has not been done before. I have just done basic testing with my current prototype and software modeling at this stage, so it is a case of wait see how it works out.
Ok, if I understood it right your unique idea revolves mainly around the PxM conversion stuff, then, have you also looked into non-linearities coming from the output inductors as I suppose you will use inductors to filter out the switching ripples?
I have got a few ideas to try out there as well, with the current prototype it's not been an issue.
Howdy, have you experience with multi-MHz switching half-bridges? I ask this because you may be a little disappointed by the 'switching' performance you get. At these frequencies you are normally using sinusoidal gate drive as there is no way to switch the gate LCR circuit sufficiently quickly for hard switching; the solution is to resonate this LCR at your desired switching frequency. This however introduces a number of drawbacks:
1) can't vary switching frequency much as this is now a tuned circuit
2) devices are not turning on and off quickly increasing losses
It's been a while since I looked at this but the last time I did the approach that stood out to me on how to achieve very high effective switching frequency was these EPC parts:
https://epc-co.com/epc/Portals/0/ep...GaN FETs for Multi-Megahertz Applications.pdf
and paralleled output devices driven as per a polyphase buck converter.
1) can't vary switching frequency much as this is now a tuned circuit
2) devices are not turning on and off quickly increasing losses
It's been a while since I looked at this but the last time I did the approach that stood out to me on how to achieve very high effective switching frequency was these EPC parts:
https://epc-co.com/epc/Portals/0/ep...GaN FETs for Multi-Megahertz Applications.pdf
and paralleled output devices driven as per a polyphase buck converter.