Hi, I resumed old project. Box, front and rear panels are ready.
I post the block diagram here.
Only the ground path is drawn - the green lines between the modules.
The ground path follows the signal path, module to module.
All modules are separate pcb's to be build.
Mby the volume control, TC 9459 would be one pcb with two vol IC's for 4 channels. Anyway, it does not require analog power supply. Signal path is not connected to the microcontroler psu.
Analog and microcontroler psu's have direct ref. point to one another (red circle on diagram).
The main idea is to use the input selector board for ground return distribution.
Signal and power ground would go along through the signal cable shield.
1. Output DAC buffers would get analog supply ground through the input selector.
p.s. Note that input selector switches ground.
- That would also switch dac buffer circuit on and off.
- That would connect analog psu ground to the DAC digital psu ground.
2. Crossover unit would get power ground through the input, via the signal cable shield.
3. The next modules (subsonic, linkwitz transform) are connected in series and would get power ground via the signal cable shield.
Analog +-15 v would also go on a bus, following the signal/ modules layout. So modules would be connected in series.
All that means that the power return path (for dozen opamps) would go along with the signal path. Power consumption current in this device is small compared to a power amp. But still few times higher than the signal current.
IS it ok to run signal and power ground together, or I shall run them on different paths?
Regards - Emil
img host
I post the block diagram here.
Only the ground path is drawn - the green lines between the modules.
The ground path follows the signal path, module to module.
All modules are separate pcb's to be build.
Mby the volume control, TC 9459 would be one pcb with two vol IC's for 4 channels. Anyway, it does not require analog power supply. Signal path is not connected to the microcontroler psu.
Analog and microcontroler psu's have direct ref. point to one another (red circle on diagram).
The main idea is to use the input selector board for ground return distribution.
Signal and power ground would go along through the signal cable shield.
1. Output DAC buffers would get analog supply ground through the input selector.
p.s. Note that input selector switches ground.
- That would also switch dac buffer circuit on and off.
- That would connect analog psu ground to the DAC digital psu ground.
2. Crossover unit would get power ground through the input, via the signal cable shield.
3. The next modules (subsonic, linkwitz transform) are connected in series and would get power ground via the signal cable shield.
Analog +-15 v would also go on a bus, following the signal/ modules layout. So modules would be connected in series.
All that means that the power return path (for dozen opamps) would go along with the signal path. Power consumption current in this device is small compared to a power amp. But still few times higher than the signal current.
IS it ok to run signal and power ground together, or I shall run them on different paths?
Regards - Emil
img host
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The main rule to follow is to avoid at any cost a 'loop'. A loop is an antenna.
There are currently two such loops easy visable in your diagram. And, with some closer inspection, even a third running from A_GND<>MCU_GND to A_GND<>DAC GND (actually it creates extra two loops).
Close the loops, keep them together.
There are currently two such loops easy visable in your diagram. And, with some closer inspection, even a third running from A_GND<>MCU_GND to A_GND<>DAC GND (actually it creates extra two loops).
Close the loops, keep them together.
Thx, but..
- Where are the two loops?
- There is no third loop:
Analog ground is connected to microcontroller PSU ground (red circle between psu's).
Analog ground is connected to the DAC digital PSU ground - through the ground commute switch (red circle in the input selector module).
No other path between them.
- Where are the two loops?
- There is no third loop:
Analog ground is connected to microcontroller PSU ground (red circle between psu's).
Analog ground is connected to the DAC digital PSU ground - through the ground commute switch (red circle in the input selector module).
No other path between them.
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Maybe is your drawing not corresponding precisely with the actual setup.
To clearify the loops, let's 'break' one of them: disconnect the green line from the PSU_analog on the right side. PSU_analog is still grounded by the wire on the left side, but the loop is broken. Same with eg the PSU_MCU block, running from there around through ~POT_F~, XO, Sub~, Link~ and ~POT_S~ and back to PSU_MCU.
Between the two ground symbols is an invisable connection. It creates two extra loops.
Elsewhere on this forum you can find Jan Didden's document about this issue (a thread with balanced-unbalanced signal lines).
To clearify the loops, let's 'break' one of them: disconnect the green line from the PSU_analog on the right side. PSU_analog is still grounded by the wire on the left side, but the loop is broken. Same with eg the PSU_MCU block, running from there around through ~POT_F~, XO, Sub~, Link~ and ~POT_S~ and back to PSU_MCU.
Between the two ground symbols is an invisable connection. It creates two extra loops.
Elsewhere on this forum you can find Jan Didden's document about this issue (a thread with balanced-unbalanced signal lines).
Nope. The ground symbols are NOT a connection to chassis or whatever.
Just used them to denote a connection between one PSU and another:
1. A_gnd to DAC_gnd via the Input Selector module
2. A_gnd to PSU_mcu_gnd
I will probably use the second as a connection to chassis.
And also, I written in the first post, that the microcontroller D_gnd and analog A_gnd are NOT connected in the Volpot_sub/ front circuits.
Thats why there is a red line denoting that. (analog | digital).
Digital control part and analog signal part of the volume chip are NOT physically connected.
Thats why PSU_Analog and PSU_Controller are seporatelly connected.
Just used them to denote a connection between one PSU and another:
1. A_gnd to DAC_gnd via the Input Selector module
2. A_gnd to PSU_mcu_gnd
I will probably use the second as a connection to chassis.
And also, I written in the first post, that the microcontroller D_gnd and analog A_gnd are NOT connected in the Volpot_sub/ front circuits.
Thats why there is a red line denoting that. (analog | digital).
Digital control part and analog signal part of the volume chip are NOT physically connected.
Thats why PSU_Analog and PSU_Controller are seporatelly connected.
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A problem might be that while I am switching off the DAC output buffer supply via the ground commute - Ground Switch 1 (connection to PSU_ANALOG gnd), the PSU_DAC gnd stays unreferenced to the system ground..
And the digital circuitry of the DAC(s) remains powered...
And the digital circuitry of the DAC(s) remains powered...
Then I will introduce ground loops (one gnd path for signal, another gnd path for power supply).
And have to break them..
F.ex. here - where to put hum breaking resistor...
Between R1 and ground?
And have to break them..
F.ex. here - where to put hum breaking resistor...
Between R1 and ground?
If we have two PCB's
Several cables carrying ground (brown color) run in parallel.
One for power, several for signal with a grounded shield).
All of them terminated on a big ground plane at each side.
May we have a ground loop which is picking noise in the dashed area ?
- see diagram attached.
Several cables carrying ground (brown color) run in parallel.
One for power, several for signal with a grounded shield).
All of them terminated on a big ground plane at each side.
May we have a ground loop which is picking noise in the dashed area ?
- see diagram attached.