Here is my first try at an LM3886 layout. I have been sitting on this design for about 10 months now, and decided to put the last touchs on it last night. Let me know what you think.
btw: I am still backlogged in mails, and will try to catch up soon.
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Brian
btw: I am still backlogged in mails, and will try to catch up soon.
An externally hosted image should be here but it was not working when we last tested it.
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Brian
Thanks,
With regards to the layout, has anyone tried adding the mute capacitor to the layout? Is this a recommended addition? The datasheet seems to like 100uF for this. I was thinking about possibly adding the cap to the layout, based on a suggestion I received.
Also, would it make sense to add a jumper for allowing the mute functionality to be switched on and off?
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Brian
With regards to the layout, has anyone tried adding the mute capacitor to the layout? Is this a recommended addition? The datasheet seems to like 100uF for this. I was thinking about possibly adding the cap to the layout, based on a suggestion I received.
Also, would it make sense to add a jumper for allowing the mute functionality to be switched on and off?
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Brian
Here is a version with the Cm cap added:
Datasheet says:
"Mute capacitance set up to create a large time constant for turn-on and turn-off muting."
The value in the datasheet is 100uF, and this will be an optional component, as is the zobel network components.
For using the larger BG capacitors, the cap can be omitted, or stuffed on the bottom of the pcb.
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Brian
An externally hosted image should be here but it was not working when we last tested it.
Datasheet says:
"Mute capacitance set up to create a large time constant for turn-on and turn-off muting."
The value in the datasheet is 100uF, and this will be an optional component, as is the zobel network components.
For using the larger BG capacitors, the cap can be omitted, or stuffed on the bottom of the pcb.
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Brian
peranders said:
How does this look for the "snubberized" rectifier board?
An externally hosted image should be here but it was not working when we last tested it.
A few extra pads can be added to the main amp board for the extra decoupling caps.
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Brian
I think you should have this snubber close to the supply pins, not far away.
I think also that the speaker trace is a bit thinn. Remember that you have at least 11 A worst case. I recommend a 150 mils trace.
I would aslo recommend that you make a decent schematic. It must be pretty easy with your cad program.
Check also the insulation distance between the screwholes and the supply planes. It's too tight according to my taste. Have you take the screw head into account?
Why don't you move all designators so you can see those even when the parts are there? It much easier to troubleshoot!
Picture here as an example. I have even drawn lines, check T10!
http://home5.swipnet.se/~w-50674/hifi_pics/hifi_100pr/qrv05r0_topview.jpg
You power supply has a but thin traces, 150 mil or even more! Route the trace to the capacitor and the route from, not add this short "inductance". It is proabaly nothing but check Joseph_K's measurements about the influence of unnecessary inductance.
I think also that the speaker trace is a bit thinn. Remember that you have at least 11 A worst case. I recommend a 150 mils trace.
I would aslo recommend that you make a decent schematic. It must be pretty easy with your cad program.
Check also the insulation distance between the screwholes and the supply planes. It's too tight according to my taste. Have you take the screw head into account?
Why don't you move all designators so you can see those even when the parts are there? It much easier to troubleshoot!
Picture here as an example. I have even drawn lines, check T10!
http://home5.swipnet.se/~w-50674/hifi_pics/hifi_100pr/qrv05r0_topview.jpg
You power supply has a but thin traces, 150 mil or even more! Route the trace to the capacitor and the route from, not add this short "inductance". It is proabaly nothing but check Joseph_K's measurements about the influence of unnecessary inductance.
?iginally posted by peranders [/i]
You shouldn't snubberize you design? Why don't you add 100 nF/63V polyester/ceramic + 1 ohms so Carlos will get happy? At least 100 nF would be good I think.[/QUOTE]
Why would I be happy?
Actually, it's time to talk about $$$$, if this is to be included in a commercial PCB.
Are you recommending the snubber now?
You shouldn't snubberize you design? Why don't you add 100 nF/63V polyester/ceramic + 1 ohms so Carlos will get happy? At least 100 nF would be good I think.[/QUOTE]
Why would I be happy?
Actually, it's time to talk about $$$$, if this is to be included in a commercial PCB.
Are you recommending the snubber now?
BrianGT said:
I'd say put it in allways
if it is providing the functionality I suspect, it should have no affect on sound, and your speakers will thank you . Ie I think what it does (based on what you quoted from the datasheet) is delay turn on of the output to stop those nasty speaker thumps/clicks. Not sure about turn off, maybe it kills the output before it starts to make any nasty noises.Tony.
BrianGT said:
Hi Brian,
I recommend you remove the snubber from your PSU PCB. Leave the large caps on but maybe have the option for two parallel caps.
Reason 1.
=======
If people what to add "the snubber" they can add it directly to the cap pins on the solder side of the pcb. This would be the optimum position anyway IMHO.
Reason 2.
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It will help keep the peace.
I'm all for intelligent discussion of snubber implementation, but can I humbly ask that all "snubber fluff" be left out of this thread. There are already a couple VERY LONG threads that are dedicated to snubber whining, crying, moaning, accussing, etc. There is also already a thread discussing how the snubber works, why it works, if it works, and in what circumstances it works. We really don't need a repeat of all this. Thanks for your co-operation.
Here is a version of the pcb along with the new rectifier board with the snubber setup:
I added additional pads for decoupling caps on the amp board so that it can follow the snubberized version. Any comments?
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Brian
An externally hosted image should be here but it was not working when we last tested it.
I added additional pads for decoupling caps on the amp board so that it can follow the snubberized version. Any comments?
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Brian
grege said:
Hi Brian,
I recommend you remove the snubber from your PSU PCB. Leave the large caps on but maybe have the option for two parallel caps.
Reason 1.
=======
If people what to add "the snubber" they can add it directly to the cap pins on the solder side of the pcb. This would be the optimum position anyway IMHO.
Reason 2.
=======
It will help keep the peace.
I don't see how it would be better to have the snubber components farther away from the large capacitor. It seems to make the most sense to leave room for it on the pcb, and if people are against using it, then the component placements can be ignored when building an amp with the pcb.
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Brian
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