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MiniSHARC based 8 channel True Digital Amplifier 8 years 8 months ago #14343

  • devteam
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Oh great progress indeed Emiel!
A full project end to end with it seems a lot of work so we certainly look forward to hearing more!

Do keep us updated as it's certainly an exciting project... :-)

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miniDSP, building a DSP community one board at a time.

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Re:Re: MiniSHARC based 8 channel True Digital Amplifier 8 years 8 months ago #14347

  • orangeart
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Starting to look good, I can't wait to see the amp part of the design. Can I ask why you are doing voltage volume control rather than just using the volume control built in digitally to the mindshare? Also how will the input switching be controlled?

Stefan

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Re:Re: MiniSHARC based 8 channel True Digital Amplifier 8 years 8 months ago #14355

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Thanks for your reactions.

@Stefan
When using digital volume control you introduce errors at higher attenuation, although I have to admit that with 32bit this isn't much of an issue. Also with increasing attenuation the signal-to-noise ratio decreases. Without digital attenuation, but with volume control implemented via the power supply voltage, the dynamic range is maintained at all listening volumes. Also we are using a microcontroller to control the volume via SPI, unfortunately MiniDSP doesn't publish the information how to implement this with the MiniSHARC kit. The microcontroller will be connected to a IR receiver and push buttons or encoders for input selection and volume control and a LCD display. Input selection is implemented by CS8416 in software mode (on the preamp board), controlled by the microcontroller. In software mode the CS8416 has 8 SPDIF inputs.

Regards, Emiel

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Re:Re: MiniSHARC based 8 channel True Digital Amplifier 8 years 8 months ago #14367

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Thanks for setting me straight about the volume control, I thought 32 bit would be more than enough for the dynamic range to not be affected at real listening levels, but I am pleased to have been put right.

Your remote control with screen sounds perfect for most people, a lot of folk have been asking for the Vol-FP to have a screen for some time now but mini-DSP are very reluctant to engage that question, maybe if they can get their hands on your board as a development project they can reverse engineer it and the Vol-FP to work together to provide this seamless functionality.

How have you implemented the USB? I ask as I use the wave-io at the moment which is a good implementation, having an on board would obviously have advantages with clocking etc but the implementation depends on a lot of other factors obviously.

Will there be i2s headers to allow the connection of USB modules like the wave-io and possibly an ADC?

Sorry lots of questions!! This is a really interesting thread. I don't seem to get time to follow many threads across the various fora these days, but have been keeping an eye on this one. Well done.

Stefan.

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Re:Re: MiniSHARC based 8 channel True Digital Amplifier 8 years 8 months ago #14389

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Your remote control with screen sounds perfect for most people, a lot of folk have been asking for the Vol-FP to have a screen for some time now but mini-DSP are very reluctant to engage that question, maybe if they can get their hands on your board as a development project they can reverse engineer it and the Vol-FP to work together to provide this seamless functionality.


Well, actually currently the microcontroller (ARM based and way 'overdimensioned' for this purpose) is on a separate board we had laying around from an earlier project. In the future it might be an idea to include a simpler microcontroller on the preamp board and maybe integrate the digital volume control of the MiniSharc in cooperation with Devteam. That might be something to develop further, after the current project is finished :laugh:

How have you implemented the USB? I ask as I use the wave-io at the moment which is a good implementation, having an on board would obviously have advantages with clocking etc but the implementation depends on a lot of other factors obviously.

USB is implemented by PCM2705C which has S/PDIF output connected to one of the CS8416's inputs.

Will there be i2s headers to allow the connection of USB modules like the wave-io and possibly an ADC?

Currently we have no I2S inputs, only S/PDIF (5x coax, 2x optical) and the USB of course.

Sorry lots of questions!! This is a really interesting thread. I don't seem to get time to follow many threads across the various fora these days, but have been keeping an eye on this one. Well done.

Don't worry about the questions! I love answering them if I can find the time, so keep them coming :woohoo:
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