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#81 | |
diyAudio Member
Join Date: Nov 2005
Location: Wales
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#82 | |
diyAudio Member
Join Date: Apr 2018
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Hello Baldin & SubSonicks-San, Here is an example adding power on/off mute on ADAU1701. DIY DSP PROCESSOR PROJECT PAGE (Solid-state mute requires negative voltage when releasing mute.) Last edited by CyberPit; 25th August 2019 at 05:12 PM. |
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#83 |
diyAudio Member
Join Date: Jan 2005
Location: Copenhagen
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Very interesting CyberPit
Thinking if it can be done even more simple ... sensing Vcc with a Zenner (here 3 diodes), and using this to mute the output at start up and close down Have not tried in reality yet ... but it seems to work in sim ... Any thoughts |
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#84 |
diyAudio Member
Join Date: Apr 2018
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Baldin-San, I also like to design as simple as possible.
There are few things to remind the constraints for real-world simulation. - DAC output waveform voltage may exceeds 0.6Vpeak from the GND level. We should prevent form the waveform peak clipping. - Need a negative voltage power supply for perfect releasing of mute-Tr driving function. - Need a reserved positive power supply after power-down. (To Keep muting after the power down) Last edited by CyberPit; 9th September 2019 at 05:17 AM. |
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#85 |
diyAudio Member
Join Date: Oct 2014
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Hey everybody! I have the exactly same problem with freeDSP SMD B:
Output 2/3 are lousy noisy! Maybe it is a layout mistake? In my opinion, the whole board is not designed really professional... I will try a linear regulator instead of the switching regulator. Any more ideas? |
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#86 |
diyAudio Member
Join Date: Oct 2014
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supplement: will at FIRST not change the voltage regular. Instead I will look around the negative supply rail for driving the mute circuit (charge pump
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#87 |
diyAudio Member
Join Date: Oct 2014
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For all who have noise problems with freeDSP SMD:
The layout is a big FAIL! ![]() seems like someone did his first try in layouting... Dear future PCB designer: First of all make a proper grounding concept. A circuit like this should have a groundplane. DON'T cut the groundplane through and through with any kinds of signals! If your layout program produces small copper islands, please leave them out instead of connecting useless 10 square millimetre islands with one via. Don't mix analog and digital signals close together. At least, take care for some ground shielding between them! Keep analog signals away from everything - especially digital signals! And yes, a charge pump running on few hundreds kHz is noisy too! If you decide to use a charge pump, don't place it close to the output filters. And again: use a lot of GND. And vias are not so expensive anymore, use more of them, they will be your friends ![]() To solve the noise problem: cut the signal lanes from DSP outputs 2/3 close to the DSP. Take a piece of thin shielded wire and connect the outputs straight to the output filters (the two 2k Resistors). I will do more modifications, mainly fixing some GND rubbish. |
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#88 |
diyAudio Member
Join Date: Oct 2014
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Further huge improvements in noise made by replacing the switching regulator (1,2MHz!!?!!) with LM317. I still can`t believe how someone can design such a bad thing and how to sell it commercially
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