SparkFun Forums

[SpikedCola]

Please be gentle, as this is the first thing I have ever designed/created in Eagle (thank you to those at SparkFun! especially those of you who created the Eagle guide - that is what taught me everything I know). Please find attached screenshots of the board, aswell as a zip containing the whole project. If you have any comments, suggestions, etc, please let me know!

EDIT Ive updated my board and schematic (havent figured out the whole polygon pour or upped the traces yet) but I fixed the ERC errors and (I think) simplified the traces and layout in general of the board

Project:
http://rapidshare.com/files/180873958/S ... d.zip.html

Original Schematic:
Here

My schematic:


Both:



EDIT 2:
Tried doing a polygon pour for ground (still have lots of optimizing left to do!):

[Shifted]

You might want to increase the size of your traces. Also look into the missing component names, it'll make assembly easier later.

[bigglez]

Project:
Original Schematic:
My schematic:
Top:
Bottom:
Both:

Please limit your embedded graphics to 640 pixels
or less. Large images distort the entire thread.

[bigglez]

Please find attached screenshots of the board, aswell as a zip containing the whole project. If you have any comments, suggestions, etc, please let me know!

What are you trying to do with this project?
The circuit is for three identical monolithic
audio power amps, driving a single load.
As these are rated for more than sixty watts
each into four ohms, do you expect to get
over 150Watts out?

There are several issues with your layout,
and a board using this design will likely not
work well, if at all, due to unintended feedback
and instabilty due to layout and inadequte
copper (trace/track width).

Has the original circuit been prototyped?

[davep238]

Please be gentle, as this is the first thing I have ever designed/created in Eagle (thank you to those at SparkFun! especially those of you who created the Eagle guide - that is what taught me everything I know). Please find attached screenshots of the board, aswell as a zip containing the whole project. If you have any comments, suggestions, etc, please let me know!
<snipped>

EAGLE 5.3 reports a number of ERC (_schematic_) errors. For the LM3886's, you have the GND and V- pins connected wrong. The leftmost pin of the bottom of the symbol is GND (pin 7), but you have it connected to V-. The pin to the right is V- (pin 4), but it is connected to GND. This problem needs to be fixed, or your board won't work. You need FAT traces for V+, V- and OUT because of high currents. Depending on how much current this amp needs, standard 0.1" headers, rated at 1 amp (2amps?) per pin, may need to be replace with higher current carrying connectors. GND should be a copper pour (polygon). Do you need mounting holes? I'd also put the SMD parts for each amp physically near each amp.
Sorry if this seems harsh.
BTW, does anyone remember seeing this board or something like it in another thread?
-Dave Pollum

[FartingMonkey92]

Look's to me like this is what you wish to achieve - diyAudio Forums - BPA300 mono block finished and measured
If you happen to be a member of diyAudio, you can grab the gerber's from this post - http://www.diyaudio.com/forums/showthre ... post787803

It'll save you alot of hassle from oscillation and the like...

[SpikedCola]

Look's to me like this is what you wish to achieve - diyAudio Forums - BPA300 mono block finished and measured
If you happen to be a member of diyAudio, you can grab the gerber's from this post - http://www.diyaudio.com/forums/showthre ... post787803

It'll save you alot of hassle from oscillation and the like...

Yes, that is where I got the original gerbers, but the board is unnecessarily large, so I decided to re-make it and try to shrink the board, to save on cost

You might want to increase the size of your traces. Also look into the missing component names, it'll make assembly easier later.

How do you do that? This is the first time Ive used Eagle, and all I know is what is in the SparkFun guides.

Project:
Original Schematic:
My schematic:
Top:
Bottom:
Both:

Please limit your embedded graphics to 640 pixels
or less. Large images distort the entire thread.

When my ship comes into port (or I find a way onto the pay-per-use internet) I will resize the pictures. Sorry about that!

Please find attached screenshots of the board, aswell as a zip containing the whole project. If you have any comments, suggestions, etc, please let me know!

What are you trying to do with this project?
The circuit is for three identical monolithic
audio power amps, driving a single load.
As these are rated for more than sixty watts
each into four ohms, do you expect to get
over 150Watts out?

There are several issues with your layout,
and a board using this design will likely not
work well, if at all, due to unintended feedback
and instabilty due to layout and inadequte
copper (trace/track width).

Has the original circuit been prototyped?

Yes, the original circuit has. I am looking to power a 200w 3ohm home theatre subwoofer with this amp. Basically, the sub isnt amped, and the little dvd player/receiver has the amp inside - but I would like to use it with a home theatre receiver, which has sub pre-outs, hence this amp. How do I increase the track size?

Please be gentle, as this is the first thing I have ever designed/created in Eagle (thank you to those at SparkFun! especially those of you who created the Eagle guide - that is what taught me everything I know). Please find attached screenshots of the board, aswell as a zip containing the whole project. If you have any comments, suggestions, etc, please let me know!
<snipped>

EAGLE 5.3 reports a number of ERC (_schematic_) errors. For the LM3886's, you have the GND and V- pins connected wrong. The leftmost pin of the bottom of the symbol is GND (pin 7), but you have it connected to V-. The pin to the right is V- (pin 4), but it is connected to GND. This problem needs to be fixed, or your board won't work. You need FAT traces for V+, V- and OUT because of high currents. Depending on how much current this amp needs, standard 0.1" headers, rated at 1 amp (2amps?) per pin, may need to be replace with higher current carrying connectors. GND should be a copper pour (polygon). Do you need mounting holes? I'd also put the SMD parts for each amp physically near each amp.
Sorry if this seems harsh.
BTW, does anyone remember seeing this board or something like it in another thread?
-Dave Pollum

Same question, how do I up track sizes? I did an ERC and it showed me the same errors but when I used the little eye it told me the pins i had connected were correct. I guess I need to double check! How do I do a polygon pour? Also, the mounting holes have yet to be added, this is just a first draft. Dont worry, your comments arent harsh at all! I just didnt want people saying "you suck at life" and not helping.

[bigglez]

Dont worry, your comments arent harsh at all! I just didnt want people saying "you suck at life" and not helping.

This is a hobby group run for the mutual benefit
of hobbyists. Thankfully we have a few seasoned
constructors (and a few industry professionals)
here to save the beginers most of the grief.

There have been very few problem members
here (who have either run off or self-destructed).
Your project is in good hands!

BTW, thanks for resizing your images! I think
you'll agree the result was worth the effort.

[bigglez]

Look's to me like this is what you wish to achieve - diyAudio Forums - BPA300 mono block finished and measured[/url]

Yes, that is where I got the original gerbers, but the board is unnecessarily large, so I decided to re-make it and try to shrink the board, to save on cost.

Compare your PCB design with the original project
shown here.
Are they the same? If not, do you expect them to
perform the same?

Go back to the PIX linked above. Notice that each
IC amplifier has it's own components in a tight
group, with very short leads. Also, the power and
output signals pass through polygon islands, not
narrow traces. The copper required to deliver
150Watts is significant. Also, the original design
used heavy screw terminals for external connections.

To change the width of a track/trace in EAGLE:
(1) Select the change tool menu (looks like a spanner/wrench)
(2) Select 'Width' menu
(3) Select desired new geometry size
(4) Select the track/trace to change in your layout
(5) Repeat for each track/trace to be changed
(6) Run DRC to look for clearance issues

[signal7]

For what it's worth, I think I gave a recommendation to the OP in another thread that it might be possible to reduce the cost of the board by making it smaller. The original board looked to me to have some excess space that could be removed depending on what components were chosen as replacements.

[SpikedCola]

Added a new version, this time with a GND pour! Its a teeny bit oversized (the image) but I hope you guys dont mind - its hard to read if I go much smaller

[bigglez]

Added a new version, this time with a GND pour! Its a teeny bit oversized (the image) but I hope you guys dont mind - its hard to read if I go much smaller

Okay, much much better! Still have some
things to work on, though.

The single most agregous issue is that you have
inputs and outputs very close together. Doing so
runs a strong risk of feedback and oscillation.
Take a second look at the trace/tracks under C1.

The power traces are still way way way too thin.
Did you follow my instructions to bump up the
trace/track width?

You may keep the thin traces for some signals
around the IC, but the power, ground, and
output have to be at the very least 250mils.

I think there's a serious error on the PCB in
the link, perhaps I'm missing something:

Isn't C11 and C12 connected backwards?

[FartingMonkey92]

How much space are you going to save by redesigning this PCB?
Because you still have to locate a hefty transformer, rectifiers
and smoothing capacitors in your enclosure, plus panel connectors...

And you'll still need a rather large heatsink to go with it, no point
skimping on that and using a smaller one after taking your time to
design the PCB and to stuff them...

[bigglez]

How much space are you going to save by redesigning this PCB?

It is/was money motivated. A smaller PCB is less cost at BatchPCB.
(Plus some lame advice before this thread got rolling).

[SpikedCola]

How much space are you going to save by redesigning this PCB?
Because you still have to locate a hefty transformer, rectifiers
and smoothing capacitors in your enclosure, plus panel connectors...

And you'll still need a rather large heatsink to go with it, no point
skimping on that and using a smaller one after taking your time to
design the PCB and to stuff them...

Hopefully a few square inches. Not to mention its helping me learn eagle, but thats besides the point. And yes, I will still need caps and a big transformer, but those can be case mounted, they dont need to be mounted on the board

Added a new version, this time with a GND pour! Its a teeny bit oversized (the image) but I hope you guys dont mind - its hard to read if I go much smaller

Okay, much much better! Still have some
things to work on, though.

The single most agregous issue is that you have
inputs and outputs very close together. Doing so
runs a strong risk of feedback and oscillation.
Take a second look at the trace/tracks under C1.

The power traces are still way way way too thin.
Did you follow my instructions to bump up the
trace/track width?

You may keep the thin traces for some signals
around the IC, but the power, ground, and
output have to be at the very least 250mils.

I think there's a serious error on the PCB in
the link, perhaps I'm missing something:

Isn't C11 and C12 connected backwards?

Theyre both non-polarized as far as I can tell.

As for upping the size of the power traces, would I be better off doing a pour for them aswell? It seems that if I up the traces I have to manually route them, there must be an easier way