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Do you really tie Analog GND and Digital GND at pin chip level in DAC/Receivers
Do you really tie Analog GND and Digital GND at pin chip level in DAC/Receivers
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Old 9th January 2019, 01:48 PM   #21
Ken Newton is offline Ken Newton  United States
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Quote:
Originally Posted by batteryman View Post
My pcb design software generates upper and lower ground planes automatically but dividing these into separate areas is more work so I have, in the past, kept the ground planes, analogue, digital and power supply grounds all separate up to the common point at the off board 0v pin. (ie the ground planes weren't connected to anything except each other)
Multi-layer boards are great. I just wish they weren't so costly as compared to double-sided boards. So, for DIY, I usually end up having to squeeze every design in to a double-sided form.

Last edited by Ken Newton; 9th January 2019 at 01:51 PM.
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Old 9th January 2019, 05:36 PM   #22
Markw4 is offline Markw4  United States
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Originally Posted by ygg-it View Post
Sorry, I forget to say that i'm using exclusively perfboards and not PCB...

Hence, not possible for me to create ground planes but I can only tie multiple wires and create multiple transformer/bridge ground separated power supplies
We create ground planes with perfboard all the time. Use copper foil for that. An example can be found in the instructions for building an ES9038Q2M output stage board here: Dropbox - Output Stage Instructions.zip
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Old 9th January 2019, 06:38 PM   #23
chris719 is offline chris719  United States
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Do you really tie Analog GND and Digital GND at pin chip level in DAC/Receivers
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Originally Posted by batteryman View Post
I would use separate ones but connect a low value inductor between them at the pcb. This keeps HF noise from getting from one to the other, whilst maintaining them at the same DC potential.
I wouldn't. Unless you want it to radiate.

Why do people think stopping the current from returning where it wants to go is a good idea?
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Old 9th January 2019, 07:08 PM   #24
MarcelvdG is offline MarcelvdG  Netherlands
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Quote:
Originally Posted by ygg-it View Post
Sorry, I forget to say that i'm using exclusively perfboards and not PCB...

Hence, not possible for me to create ground planes but I can only tie multiple wires and create multiple transformer/bridge ground separated power supplies
How about dead bug style build-up on a single-sided copper-clad board (that is, unetched PCB) or simply on a beer or soft drink can that's been cut open? That's not ideal for a DAC, but at least it gives you a solid ground plane.
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Old 9th January 2019, 08:04 PM   #25
00940 is offline 00940  Belgium
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Originally Posted by MarcelvdG View Post
How about dead bug style build-up on a single-sided copper-clad board (that is, unetched PCB)
An effective variation on that theme is to use a single sided copper clad board and then glue on it smaller pieces of the same for power lines and so on. Search for "Manhattan style" prototyping.
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Old 9th January 2019, 08:25 PM   #26
MarcelvdG is offline MarcelvdG  Netherlands
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I know the technique, but had never heard of the term Manhattan style. Another variant uses pieces of board with copper traces on 2.54 mm pitch to solder DIL ICs and other components on, after those pieces are glued to a copper-clad board. That requires etching of those pieces of board, though.

Maybe you could even use pieces of perfboard for it and either make sure that the component leads do not stick through the holes, or rely on the glue layer as insulator (if the voltage is not too high).
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Last edited by MarcelvdG; 9th January 2019 at 08:36 PM.
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Old 9th January 2019, 08:45 PM   #27
TNT is offline TNT  Sweden
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Quote:
Originally Posted by ygg-it View Post
Sorry, I forget to say that i'm using exclusively perfboards and not PCB...

Hence, not possible for me to create ground planes but I can only tie multiple wires and create multiple transformer/bridge ground separated power supplies


So question is:

should I have two ground wires (digital and analog) from Power supply (transformer/bridge ground separated?) to the dac/receiver digital and analog ground pins

or

one wire from power supply to the dac/receiver joined digital and analog pins?
Method of Applying a Copper Ground Plane to Strip-board (e.g. Veroboard): 10 Steps

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Old 10th January 2019, 05:13 AM   #28
ygg-it is offline ygg-it  Italy
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Thanks for all kind replies and for the "Manhattan"/copper tips!

But, I'm going to build a dac with 4 PCM56 in parallel, thus eight 16-pin chips, each of them with +/-5V analog and +/-5V digital.

So I have: 4 wires for power supply, 1 or 2 wires for grounds (depend on this thread), 4 wires for inputs, one wire for current output, plus some trimming resistors.

Multiply this by eight (4 x 2 channels) and put on a 15X10 cm board, plus decoupling capacitors, ferrites, input/output pin. And this is excluding receiver, separate power supplies, PLL re-clock and analogue stage which are all on different boards with separate transformer (my DAC is becoming a “cupboard”, but I’m happy the same for the result I’m getting…)

The only way to use a copper plane would be stacking the PCM56 chips, which works (I tested!), but I don't like soldering chips one over the other in a definitive project. I need also to roll and select them for the lowest MSB THD.

I have to stay on perfboard single wiring. Even a PCB would not create a real plane but several ground loops and crossing paths in such multiple chips small area.

Question now is: until I don't hear any noise in the speaker at very low source volume, it would mean that my ground solutions are ok? Or could be that “wrong grounds designs” are inaudibile?
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Old 10th January 2019, 06:06 AM   #29
chris719 is offline chris719  United States
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Do you really tie Analog GND and Digital GND at pin chip level in DAC/Receivers
Quote:
Originally Posted by ygg-it View Post
Thanks for all kind replies and for the "Manhattan"/copper tips!

But, I'm going to build a dac with 4 PCM56 in parallel, thus eight 16-pin chips, each of them with +/-5V analog and +/-5V digital.

So I have: 4 wires for power supply, 1 or 2 wires for grounds (depend on this thread), 4 wires for inputs, one wire for current output, plus some trimming resistors.

Multiply this by eight (4 x 2 channels) and put on a 15X10 cm board, plus decoupling capacitors, ferrites, input/output pin. And this is excluding receiver, separate power supplies, PLL re-clock and analogue stage which are all on different boards with separate transformer (my DAC is becoming a “cupboard”, but I’m happy the same for the result I’m getting…)

The only way to use a copper plane would be stacking the PCM56 chips, which works (I tested!), but I don't like soldering chips one over the other in a definitive project. I need also to roll and select them for the lowest MSB THD.

I have to stay on perfboard single wiring. Even a PCB would not create a real plane but several ground loops and crossing paths in such multiple chips small area.

Question now is: until I don't hear any noise in the speaker at very low source volume, it would mean that my ground solutions are ok? Or could be that “wrong grounds designs” are inaudibile?
You could produce something that is audibly fine but radiates and/or is susceptible to EMI. It might not be a real concern, though, for a one-off hobby project.

You might not achieve the datasheet specs, but it might not be audible either.
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Old 10th January 2019, 06:10 AM   #30
Mark Whitney is offline Mark Whitney  Netherlands
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Perhaps noise/distortion increases with volume. With higher currents, you get higher voltages and increased coupling along wires, traces and planes.


Remember, the layout is the circuit.
Prevent ground loops and always keep the loop area small.
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Last edited by Mark Whitney; 10th January 2019 at 06:15 AM.
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