BPA PCB Layout with servo. Comments/Suggestions?

Arx · 23rd July 2007, 06:25 PM

I have a tentative PCB layout for a BPA board with DC servo.

I think the only especially cluttered part is right over the chip I have a decoupling cap and muting resistor drawn in the same place. The muting resistor will actually be bent outwards towards the chip.

To make it a little easier to understand, the power ground plane is on the component side on the top half of the board (Red), and the signal ground is on the Solder side on the bottom half of the board (green). They will be connected back at the power supply.

Any comments?

Would anyone be interested in some PCBs? I'm probably just going to etch it myself, but if there's sufficient interest I might get some made up.

-Nick

Oh yeah.. The schematic and boards are at http://arx.ca/projects/BassAmp

Without the zones, for clearer reading:

tiltedhalo · 24th July 2007, 12:47 AM

Just a quick question, why a TLO72? I believe you would want a servo to have a better slew rate then the LM3886.

Leolabs · 24th July 2007, 03:35 AM

Quote:

Originally posted by tiltedhalo
Just a quick question, why a TLO72? I believe you would want a servo to have a better slew rate then the LM3886.

Why not??I did see some new design still using the TLO72 as servo,although OP27/37 is more popular.

AndrewT · 24th July 2007, 09:37 AM

or the really old lm411 for a servo.

The servo does not need a fast slew.
low offset and good DC stability are much more important.
The servo works better if you filter (Rs13+Cs8) the signal before it reaches the opamp. The servo never sees a fast signal.
And also filter the output before you feed that back into the chipamp.

Why all the cramped components around the chip?
and acres of unused space else where on the PCB?

Arx · 24th July 2007, 08:37 PM

AndrewT:

I guess I should post a new schematic with the correct annotations when I get home. Rs13 and Cs8 are still there, they're just called Rs3 and Cs2 now.

I was aiming for a relatively short feedback loop. (Don't know how much this really matters, but a lot of people seem to think so) And wanted to put the smallest bypass caps very close to the chip, which caused a little bit of crowding.

The muting resistor I can probably move, though. I'll probably have a look at that tonight.

-Nick

23rd July 2007, 06:25 PM	#1
Arx diyAudio Member Join Date: Aug 2003 Location: North Vancouver, B.C.	BPA PCB Layout with servo. Comments/Suggestions? I have a tentative PCB layout for a BPA board with DC servo. I think the only especially cluttered part is right over the chip I have a decoupling cap and muting resistor drawn in the same place. The muting resistor will actually be bent outwards towards the chip. To make it a little easier to understand, the power ground plane is on the component side on the top half of the board (Red), and the signal ground is on the Solder side on the bottom half of the board (green). They will be connected back at the power supply. Any comments? Would anyone be interested in some PCBs? I'm probably just going to etch it myself, but if there's sufficient interest I might get some made up. -Nick Oh yeah.. The schematic and boards are at http://arx.ca/projects/BassAmp Without the zones, for clearer reading:

24th July 2007, 12:47 AM	#2
tiltedhalo diyAudio Member Join Date: Sep 2005 Location: Melbourne Florida	servo Just a quick question, why a TLO72? I believe you would want a servo to have a better slew rate then the LM3886.

24th July 2007, 09:37 AM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	or the really old lm411 for a servo. The servo does not need a fast slew. low offset and good DC stability are much more important. The servo works better if you filter (Rs13+Cs8) the signal before it reaches the opamp. The servo never sees a fast signal. And also filter the output before you feed that back into the chipamp. Why all the cramped components around the chip? and acres of unused space else where on the PCB? __________________ regards Andrew T.

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24th July 2007, 08:37 PM	#5
Arx diyAudio Member Join Date: Aug 2003 Location: North Vancouver, B.C.	AndrewT: I guess I should post a new schematic with the correct annotations when I get home. Rs13 and Cs8 are still there, they're just called Rs3 and Cs2 now. I was aiming for a relatively short feedback loop. (Don't know how much this really matters, but a lot of people seem to think so) And wanted to put the smallest bypass caps very close to the chip, which caused a little bit of crowding. The muting resistor I can probably move, though. I'll probably have a look at that tonight. -Nick

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