Hi guys.
I have an idea in mind, and I'd like to know your opinions.
A regular Minidsp 2x4HD system is like this
Source -> [Minidsp DSP -> DAC ] -> Power amplifier.
I know the Minidsp DAC is not bad, but it is not the best, and instead of expending in a DSP Digi and a DAC, what if I use the I2S outputs on the minidsp to feed a Class D amp digitally.
Most Class D amplifier turns analog input signal into a PWM to feed the power stage. But there are some that take a I2S digital input and turn this into the PWM. So there won't be a need for DAC.
I'm thinking on TAS5760M
What do you think? Have any of you tried something like this? How good are those digital input class D amplifiers in general?
Best regards,
Jose
I have an idea in mind, and I'd like to know your opinions.
A regular Minidsp 2x4HD system is like this
Source -> [Minidsp DSP -> DAC ] -> Power amplifier.
I know the Minidsp DAC is not bad, but it is not the best, and instead of expending in a DSP Digi and a DAC, what if I use the I2S outputs on the minidsp to feed a Class D amp digitally.
Most Class D amplifier turns analog input signal into a PWM to feed the power stage. But there are some that take a I2S digital input and turn this into the PWM. So there won't be a need for DAC.
I'm thinking on TAS5760M
What do you think? Have any of you tried something like this? How good are those digital input class D amplifiers in general?
Best regards,
Jose
What you propse will work excellent,
IF there would be absolutely zero variation in the voltage supply rails to the power amplifier
AND the load remains constant through all frequencies and all power level,
The reality is of course that the load is very complex and the voltage rails will jump up and down depending on load and supply regulation variations.
To fix that issue designers use feedback and correction to accomodate these errors to the best of the chosen method, designers ability and amplifer cost target.
The best idea is ofcoz to use an ADC and get the feedback digitally to digitally correct output errors.
(Analog to Digital Converter)
The crux of that problem is that A to D Conversion takes comparatively long time to process if you desire good resolution, we are talking 10's to 100 microseconds... (+ microprocessing time) and this means that the amplifer if trying to correct for something that happened(went wrong) several switching cycles ago.
There are probably more issues but these are main ones I see.
IF there would be absolutely zero variation in the voltage supply rails to the power amplifier
AND the load remains constant through all frequencies and all power level,
The reality is of course that the load is very complex and the voltage rails will jump up and down depending on load and supply regulation variations.
To fix that issue designers use feedback and correction to accomodate these errors to the best of the chosen method, designers ability and amplifer cost target.
The best idea is ofcoz to use an ADC and get the feedback digitally to digitally correct output errors.
(Analog to Digital Converter)
The crux of that problem is that A to D Conversion takes comparatively long time to process if you desire good resolution, we are talking 10's to 100 microseconds... (+ microprocessing time) and this means that the amplifer if trying to correct for something that happened(went wrong) several switching cycles ago.
There are probably more issues but these are main ones I see.
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Its hopefully enough for the speaker rails to be sufficiently well regulated - "absolutely zero variation" isn't a physical reality, nor necessary - linear voltage droop with load is going to contribute to the damping factor, not the distortion per se. However if you use LC filter components on the output then you have inductor distortion to worry about, and a feedback loop can do useful work to linearize this.
Another approach is to use an analog amp as an error-corrector for the main switch-mode amp, and a DAC to provide the reference for the error corrector. This idea is most of the power is handled in switchmode for efficiency, but the errors are corrected in the analog domain. I'm sure there are a lot of attempts at this - with varying success, and its quite complex as the switching tone has to be filtered out from the analog side and the phase-response of the digital and analog sides have to be well matched across the audio spectrum.
Another approach is to use an analog amp as an error-corrector for the main switch-mode amp, and a DAC to provide the reference for the error corrector. This idea is most of the power is handled in switchmode for efficiency, but the errors are corrected in the analog domain. I'm sure there are a lot of attempts at this - with varying success, and its quite complex as the switching tone has to be filtered out from the analog side and the phase-response of the digital and analog sides have to be well matched across the audio spectrum.