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Old 12th July 2004, 05:37 PM   #11
squadra is offline squadra  Netherlands
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Quote:
Originally posted by janneman
Getting better all the time. You may want to put the input gnd pad close to the input hot pad, makes it easier to solder the screened cable from the input. Run this pad with a short track to the start gnd.

The speaker output pad seems floating, or is there a jumper? Anyway, move the speaker pad to the right side of the electrolytic. Avoids speaker current under the cap. Also, move the V+ and V- pads closer to the chip, above the elcap, makes your pcb more compact and avoids unnessesary track length.

Jan Didden
Upupa & Jan, thanks for the comments & compliments, keep them both coming

Pin 3 of the LM3886 is bent a little forward and is soldered in the hole marked '3' in the speaker trace.

I will redo the design, guess I can go to 5 x 3 cm for the complete pcb.
Maybe it would be a good idea to move the lm3886 to the side of the pcb, although that would require the use of a wire for V-?

Pj
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Old 12th July 2004, 07:32 PM   #12
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Try to avoid jumpers, especially in high-current tracks. They may be fine now, but a year from know who knows, what with all the air polution and possibly not fully perfect soldering.

Jan Didden
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Old 12th July 2004, 07:46 PM   #13
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To squadra : Now is it more better , but try it little more arrange - remember that universe is symetrical .
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Old 12th July 2004, 07:57 PM   #14
cjd is offline cjd  United States
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You can do it without jumpering the power tracks.

Click the image to open in full size.

This is 25x45mm or thereabouts. (grid is 1/10 inch or 2.54mm)

It has been recommended that R3 go to power ground vs. Signal ground and I'm tweaking to this end. Also was suggested to eliminate Cb on this layout. The only reason I post here is to show it *can* be done. My own experience (or, I should say relative lack of experience) has me a little uncomfortable with anyone actually using my designs. (I've been working on this for a week or two and never had done PCBs before - but many have helped here, including Pedja - quite a helpful bunch, to which I am grateful). To that end, and to minimize the PCB size some, I have moved the zobel off-board (a pad for one end of the cap, one end of the R - a little P2P seems acceptable for a circuit most don't even use) and put the output resistor sideways (keeps the output away from the input). This is also intended for use with a regulated power supply, hence less room for power caps. I've also rotated the power caps 90 degrees (clockwise for V-, counter-clockwise for V+) to move the pins closer to the chip. Without the zobel or Cb in the network, this is closer than this version would allow.

Note, there *is* a jumper here, but it is used to connect Signal with Power ground, a connection that is almost always suggested to be "difficult" if that's an acceptable term. So, in this case, the disadvantages of a jumper end up being an advantage.

keep at it.

One thing that has come up that I'm curious about - is there a problem with running a trace through one of the unused pins on the chip without removing the pin? It seems to me it wouldn't be a good idea, but asking never hurt anyone... I hope.

C
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Old 12th July 2004, 09:43 PM   #15
squadra is offline squadra  Netherlands
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Quote:
Originally posted by Upupa Epops
To squadra : Now is it more better , but try it little more arrange - remember that universe is symetrical .
Hi Upupa,
The newest version is attached, it is more symmetrical.

Quote:
Originally posted by cjd
You can do it without jumpering the power tracks.

This is 25x45mm or thereabouts. (grid is 1/10 inch or 2.54mm)

It has been recommended that R3 go to power ground vs. Signal ground and I'm tweaking to this end. Also was suggested to eliminate Cb on this layout. The only reason I post here is to show it *can* be done. My own experience (or, I should say relative lack of experience) has me a little uncomfortable with anyone actually using my designs. (I've been working on this for a week or two and never had done PCBs before - but many have helped here, including Pedja - quite a helpful bunch, to which I am grateful). To that end, and to minimize the PCB size some, I have moved the zobel off-board (a pad for one end of the cap, one end of the R - a little P2P seems acceptable for a circuit most don't even use) and put the output resistor sideways (keeps the output away from the input). This is also intended for use with a regulated power supply, hence less room for power caps. I've also rotated the power caps 90 degrees (clockwise for V-, counter-clockwise for V+) to move the pins closer to the chip. Without the zobel or Cb in the network, this is closer than this version would allow.

Note, there *is* a jumper here, but it is used to connect Signal with Power ground, a connection that is almost always suggested to be "difficult" if that's an acceptable term. So, in this case, the disadvantages of a jumper end up being an advantage.

keep at it.

One thing that has come up that I'm curious about - is there a problem with running a trace through one of the unused pins on the chip without removing the pin? It seems to me it wouldn't be a good idea, but asking never hurt anyone... I hope.

C
Hi cjd,

With your 2 weeks you are far more experienced than I am, this is my 3rd day as pcb designer
There are indeed a lot of people helping eachother here, I've learned a lot just lurking.

If I'm correct then R3 is part of the feedback network, it doesn't seem right to 'polute' that with garbage from the power.
Of course I could be mistaken, I'm no expert, that's for sure

The attached PCB is 50 * 35 mm, I've read that at least 2 mm should be left for cutting the pcbs.
That's 46 * 31 mm effective board area.

I made a comprimise, there is now a trace below the LM3886 for V- and it can be jumpered.

If there is any danger in connecting a NC pin to some other trace I don't know.
I decided to avoid any problems and read Reserved instead of NC, so I will cut pin 2 & 6.

Thanks for your input,

Pj
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Old 12th July 2004, 09:56 PM   #16
Franz G is offline Franz G  Switzerland
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There is no danger to connect the NC-pins, because they are not connected (I tried it with one of my first boards).

Maybe it is the better idea, than to cut some pins : they help to get some heat out of the chip. So, give them some copper and solder, just a little bit, and dont cut them!

Franz
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Old 12th July 2004, 10:23 PM   #17
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To squadra : Absolutely perfect, go on .
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Old 13th July 2004, 02:45 AM   #18
cjd is offline cjd  United States
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The universe is balanced, not symmetrical.

Moving V- to the same "side" of the board as V+ cuts out a lot of trace on the V- side with the 3886.

And, R3 *is* part of the feedback and, as it was explained to me, that should all go directly to the main (power) ground star (vs Signal ground, which is then attached to the power grund star).

It does look good though. It won't be something you can mount up to the side of the case or similar as is common, but that's not a problem by itself.

Franz G: I like hearing I can run traces through NC pins. Helps keep paths shorter, and if there really is no reason to clip them it helps other ways (as you mentioned).

C
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Old 13th July 2004, 12:45 PM   #19
squadra is offline squadra  Netherlands
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Default And now for something completely different

The pcb for the PS buffering...
I am going to use 3 * 1000uF/63 for each rail.
That should be enough for a single LM I guess.

The rectifiers will be connected to a metal plate for cooling, so no pcb is needed for that.

Thanks again everybody for your input.
So far it has been a lot of fun
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Old 13th July 2004, 02:01 PM   #20
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For this output power use standard bridge such as KBUJ 8, which you can give directly to this PCB. Don't belive to anything who will say to you, that you need some exotic ones - it says only ones, who don't know design correct PCB. With bridge on PCB commonly with elyts you get shortly wires, which is more significant than any exotic bridge or diodes.
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