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Old 18th September 2011, 07:04 PM   #21
Reality first!
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Quote:
Originally Posted by soongsc View Post
I recall Mauro provided a good list on layout practices, as usual the devil is in the details.
Yes, I've read it.

And I'm reading other interesting documents too.

Quote:
Originally Posted by soongsc View Post
Not too long ago working on a different design, I discovered that any two components placed close together will interact with each other, due to the electromagnetic effect of the small amounts of current. So it's also a good practice to check the direction so that these sort of run perpendicular to each other.
Can you elaborate, please?

Thanks
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Old 19th September 2011, 01:28 AM   #22
soongsc is offline soongsc  Taiwan
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I'll try to explain using the example of two wires, if you have two wires running in parallel, but the currents are running in opposite directions, then each conductor will be under the influence of the magnetic field generated from current running in the other conductor, to minimize this effect, you can have the traces jump over each other, or if the traces are further away from each other, the influences are minimized. If they have to be close together and in parallel, currents running in the same direction is much better than in opposite directions. When it comes to components, if you have caps or resistors jumping over traces, then the currents are most likely to be running perpendicular to each other, but do take note of how the cap and resistor structure might change the current/magnetic field direction.

Oh, also keep the higher current sections away from the inputs of lower current sections. Someone did a mistake here in one of my amps, and the results were sound more dead and compressed accompanied with higher distortion measurements.
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Last edited by soongsc; 19th September 2011 at 01:38 AM.
 
Old 19th September 2011, 10:20 AM   #23
Rudy is offline Rudy  Belgium
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D3 doesn't work !
Downside of using 2 bridges.

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Old 19th September 2011, 11:14 AM   #24
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D3 doesn't work !
Downside of using 2 bridges.
Hi Rudy,

do you mean that D3 should be connected to NAC1, right?

Take a look on the updated schematic, now it should work...

Thanks

PS

Soongsc, is it any better now?
Attached Images
File Type: jpg RevO - Schematic.jpg (213.9 KB, 147 views)
File Type: jpg RevO - PCB.jpg (332.5 KB, 138 views)
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Last edited by ClaveFremen; 19th September 2011 at 11:35 AM.
 
Old 19th September 2011, 05:23 PM   #25
soongsc is offline soongsc  Taiwan
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Is this a double sided board? What do the blue and different shades of red represent?
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Old 19th September 2011, 05:45 PM   #26
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Is this a double sided board? What do the blue and different shades of red represent?
Yes, Soongsc, it's a doule sided board.

Red is the component side, blue the solder side.

Red is transparent so the darker red represents a trace in the bottom layer.

In the meanwhile I've updated the PCB
Attached Images
File Type: jpg RevO - PCB.jpg (335.0 KB, 118 views)
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Last edited by ClaveFremen; 19th September 2011 at 05:58 PM.
 
Old 19th September 2011, 06:11 PM   #27
soongsc is offline soongsc  Taiwan
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It's going to take a while to trace the schematic though the PCB.
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Old 19th September 2011, 07:57 PM   #28
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It's going to take a while to trace the schematic though the PCB.
Yes, it's not so easy... I've attached some pics to help.
Attached Images
File Type: jpg RevO - Amp circuit.jpg (212.5 KB, 108 views)
File Type: jpg RevO - Amp circuit (detail).jpg (235.0 KB, 100 views)
File Type: jpg RevO - LM3886 Power supply decoupling.jpg (187.1 KB, 20 views)
File Type: jpg RevO - LM318 Power supply.jpg (142.9 KB, 22 views)
File Type: jpg RevO - Power supply - Main ground.jpg (174.6 KB, 18 views)
File Type: jpg RevO - DC Protection.jpg (245.3 KB, 21 views)
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Old 20th September 2011, 05:31 AM   #29
soongsc is offline soongsc  Taiwan
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The way you have the ground plane laid out is going to complicate things. Remember the old Rev C does not have a ground plane like that for a good reason. The circuits have less unaccounted capacitance in the signal path. I would only use this kind of ground for power voltage distribution. All the EMI shielding should be done using the chassis.

The amp output ground seems really close to the input ground. Not a good idea because that ground is still a high current point and it's going to effect the input. Unless you have done some analysis, and determine that is what you really want, generally, I would avoid it. It might be interesting to do some experiments though to see how if effects measurements and sound.

I'll continue to look through the amp section first, but those gray component markings really make it hard to read.
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Old 20th September 2011, 10:43 AM   #30
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The way you have the ground plane laid out is going to complicate things. Remember the old Rev C does not have a ground plane like that for a good reason. The circuits have less unaccounted capacitance in the signal path. I would only use this kind of ground for power voltage distribution. All the EMI shielding should be done using the chassis.
I've taken inspiration from the MY_EVO (Evolution) PCB, I've attached the only officially available pic (from the assembly manual).

Obiously it's possible that my version is wrong...

Quote:
Originally Posted by soongsc View Post
The amp output ground seems really close to the input ground. Not a good idea because that ground is still a high current point and it's going to effect the input. Unless you have done some analysis, and determine that is what you really want, generally, I would avoid it. It might be interesting to do some experiments though to see how if effects measurements and sound.
Yes but the TP RevC PCB is not much different in that regard...only 2 cm more distant.

I'll try to gain distance.

Maybe I can avoid the overlap of the 0V plane (signal ground) with OGND trace, it can help?

Quote:
Originally Posted by soongsc View Post
I'll continue to look through the amp section first, but those gray component markings really make it hard to read.
I've attached a new version of the amp detail with green component marking, I hope it will help you.

I appreciate very much your comments and your help, Soongsc, thanks!
Attached Images
File Type: jpg REvC detail.jpg (190.1 KB, 31 views)
File Type: jpg RevO - Amp circuit (detail).jpg (225.1 KB, 21 views)
File Type: jpg my_evo.jpg (304.6 KB, 60 views)
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Last edited by ClaveFremen; 20th September 2011 at 10:46 AM.
 

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