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Old 15th January 2013, 07:57 PM   #61
qusp is offline qusp  Australia
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Quote:
Do I not read the recommended layout from ESS right?
yes thats the problem, something I think Diyinhk did as well, though the many instructions to avoid splitting the ground plane/return should have been a hint

Quote:
I can see that diyinhk has replicated the layout recommendation in p.6 of the same document you quoted. There the input signal also crosses the "massive" power lines at a right angle.
no he doesnt, in the app note the IV resistor is first before the split and the rails are on the top side and are solid planes split by that line, not thick traces splitting the ground plane on that line, only the feedback paths cross the gap in the power planes and given the feedback the error should be somewhat mitigated. but yes I would take this further, given the regulators arent on the board anyway. there is no need for the inputs to disturb the ground plane at all under any circumstance.

Quote:
Output Section
The output section expanded in Figure 6 shows the opamps, filters, and XLR and RCA connectors.

Figure
6 shows one of the eight identical output stages on the evaluation board. The top copper layer of the PCB is shown in red, the bottom is shown in dark blue and notes for the purpose of this document are in green.
The +12V and -12V split planes are shown separated by the coral colored lines. The +12V and -12V split planes provides solid connections (circled in green) to the power supply for the outputs. Ensure that the
connection to the rest of the plane is solid and not cut off on an island due to other traces being routed on the top layer.

Last edited by qusp; 15th January 2013 at 07:59 PM.
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Old 15th January 2013, 08:15 PM   #62
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Is there a practical difference between crossing the power lines with a trace or with a resistor?. I do notice the resistors are before the power lines, but you still have to cross the power lines with a trace. (and if so could you link to a reference?)

I've taken a closer look at the actual implementation of what is recommended in the ESS documents, ie, the evaluation boards that can be purchased from the distributors (I don't have one, but have pictures)

There the power lines are not in the top, so must be in the bottom. The top ground fill is also split along the middle of the opamps. The layout recommendations in the document shows the power lines running under the opamps.

If you have a photo of the bottom of the evaluation board, could you forward the link?

But your suggestion about ground is welcomed.

Suggestion for next versions: have left and right power input so as to allow a wide center uninterrupted ground plane in the middle of the board. (In other words break the power lines in the middle so as to have right and left power lines)

I've also traced the signal lines from DAC to opamp on the bottom side of the board and the return under the signal lines is pretty clean from the power lines to the DAC.

What pins are the signal return paths in the opamp?
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Old 15th January 2013, 08:32 PM   #63
qusp is offline qusp  Australia
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there are no power lines, there are power planes, the coral lines are splits/edges of power planes and they talk about not sharing ground vias, if the ground plane was on the top there would be power vias, not ground vias.

the only trace that splits the top is AVCC, a completely quiet and constant AVCC/2, but the ground is solid under it except for a couple of short lengths of feedback trace which dont block the return.

but look its not my job to fix a manufacturers layout, neither is it yours.

Quote:
the ground plane may be divided underneath the DAC as shown. The top side is kept clear from traces to provide a solid AVCC connection on the flooded plane.

Last edited by qusp; 15th January 2013 at 08:37 PM.
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Old 15th January 2013, 08:39 PM   #64
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Originally Posted by qusp View Post
there are no power lines, there are power planes, the coral lines are splits/edges of power planes and they talk about not sharing ground vias, if the ground plane was on the top there would be power vias, not ground vias.

but look its not my job to fix a manufacturers layout, neither is it yours.
I took a look at the top and bottom artwork in the ESS docs. The power lines are not there. So likely it is a 4-layer board.

In any case, the bottom layer (GND) is clear in between the opmaps, so splitting the power lines into left and right is a good suggestion (I think).

This is a diy board. Many manufacturers have benefited from the input of people here. I have no problem sharing my ideas...
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Old 15th January 2013, 09:01 PM   #65
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ive not ever seen the board in the flesh and they arent explicit in the document.

it doesnt have to be a 4 layer board though and I actually doubt it is. I didnt suggest they are on the bottom. the top is sectioned into power planes and the trace you think is splitting the top plane, is rather just travelling in the gap between the positive and negative power planes.

if its a 4 layer board they havent made very good use of it, there would be no need to have the signal jump between layers for the feedback path if they had 4 layers. nah look at figure 7, its 2 layers; there is no way they would laid it out like that with 4 layers. btw the X's are net points, they stand for output/input pins, power connections, layer changes and ground vias.

*its possible its 4 layers I guess nothing rules it out, but that just takes me to my next point

on top of this, I think weve been working with the ess long enough to offer some improvements on the 9008 eval board dont you?

at this point glt, i'm helping you, not the manufacturer, despite not getting a great deal of encouragement. I get frustrated, I let that show, its taken me what 3 weeks to try and get this point through?

Last edited by qusp; 15th January 2013 at 09:18 PM.
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Old 15th January 2013, 09:19 PM   #66
glt is offline glt  United States
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Originally Posted by qusp View Post
...
at this point glt, i'm helping you, not the manufacturer, despite not getting a great deal of encouragement. I get frustrated, I let that show, its taken me what 3 weeks to try and get this point through?
I certainly hope you are enjoying this. You are one of the most prolific posters...

It has taken this long because not everyone (or even hardly anyone) is at your level...
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Old 15th January 2013, 09:33 PM   #67
qusp is offline qusp  Australia
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I certainly hope you are enjoying this
not really, I just dont like a job unfinished

which it seems to be, plenty of other stuff, but those are the major ones and I dont have the energy. i'm dwarfed by those that surround me, standing on the shoulders of giants I believe. I have a LOT to learn.

whats that saying?

Quote:
The more I learn, the more I realize I don’t know. The more I realize I don’t know, the more I want to learn.
– Albert Einstein

good luck.

Last edited by qusp; 15th January 2013 at 09:49 PM.
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Old 15th January 2013, 11:26 PM   #68
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Originally Posted by qusp View Post
whats that saying?

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The more I learn, the more I realize I donít know. The more I realize I donít know, the more I want to learn.
Ė Albert Einstein
Ἓν οἶδα ὅτι ουδὲν οἶδα [= I know one thing: that I know nothing]

Socrates
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Old 15th January 2013, 11:44 PM   #69
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Originally Posted by TheShaman View Post
Ἓν οἶδα ὅτι ουδὲν οἶδα [= I know one thing: that I know nothing]

Socrates
and ignorance is bliss eh ?

"Knowledge puffs up but love builds up" St. Paul.

Group hug people ?
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Old 15th January 2013, 11:57 PM   #70
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And all of this, dear friends, is why it is actually best to buy a pcb designed by someone who knows what they're doing rather than just the cheapest pcb that takes the DAC chip that you think you want. The datasheet pcb design is the minimum standard to achieve IMO. I know I am flogging a dead horse here, but, why exactly did qusp need to explain all that is wrong with a flawed product? Why did he need to spend HOURS writing all of that stuff that is nothing more than repeating publicly available information on the DAC implementation and basic PCB design principles? As he's admitted there is still plenty to PCB design improvements that are left to implement after the changes he has suggested. He is mostly concerned with maintaining a minimum standard for DIY audio pcb design, there is still plenty of room for improvements past this and still there is very little savings by having built (and compromised) a lot of expensive parts onto a cheap PCB. I just do not understand the logic here.

Last edited by hochopeper; 16th January 2013 at 12:08 AM.
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