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Old 25th January 2009, 01:26 AM   #11
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by Ted205
would be a shame to have the psu connected as the only option.

I actually modified the design to add pads to the V+ and V- traces, in order to run it by itself, putting a cut line on the bottom of the PCB to cut the top 2" off to form just an amp board. I will post pics for this later, as I am away from that computer now.

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Old 25th January 2009, 11:34 AM   #12
AndrewT is offline AndrewT  Scotland
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Default Re: Re: Re: new LM4780 layout, any comments?

Quote:
Originally posted by BrianGT
Here is a similar layout that I made for the LM3886, which I haven't finished fully yet.
There is an external report that is linked from this Forum saying that pin7 sends out a dirty current.
Don't connect it to Signal Ground (SG).
There is room to take a separate trace to the Audio Ground (AG).

What about space for RF attenuation at the input? Or do you solder the cap on the back of the PCB @ R3 location?
If you move R3 & R4 slightly right to leave space for a 330pF to 1nF cap and take SG with them, then there is room to move C6 to the other side of SG.
That then leaves the optional space for a DC blocking cap on the input. Keep three input pins SG, AC, DC, @ 0.1inch pitch.
Jumper SG & AC for testing, jumper AC & DC for bypassing the input cap, leave jumper on DC for AC coupled input. solder the input cable from the RCA to the back of SG & AC.

Remove pins 2 & 11, leaving more room for the adjacent traces.

After all this is there room to add a 10r to the trace from SG to AG?

If you saw the PCB just above R8, then add a couple of pads to the V+ & V- traces on both halves of the PCB.
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Old 26th January 2009, 09:11 PM   #13
Atilla is offline Atilla  Norway
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I've a few questions, out of curiosity, basically.

Why not attach the leds trough the bleeder resistors, instead of adding seperate tracks? The currnet through the bleeders is wasted anyway, might as well use it for something more. Or this is not a good idea, due to something I'm missing?

Maybe add a track for an (optional) snubber as well, for people that might want to install it.
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Old 27th January 2009, 11:19 AM   #14
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Hi Brian,

I am not an expert by any means but I have some comments:

R9 for muting seems low at 1k, is it 10k maybe?

R10/11 snubbers seem large at 1k, I would use something around 1R

also you might want to consider putting some optional 22uf-150uf capacitors between R7/R8 and GND

although it might be against your philosophy, you could use soft-recovery bridge rectifiers instead of MUR860's.

lastly capacitors C3-C6. I know you use a similar scheme in your LM3886 kits but I think it might sound slightly brilliant. I would go for 1x or 2x 470uf / rail but probably testing is the best route.

the layout is very neat - nice one

Evan
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Old 12th February 2009, 04:53 PM   #15
sasmit is offline sasmit  India
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this looks very much like the reference pcb artwork in the national datasheet
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Old 12th February 2009, 04:57 PM   #16
sasmit is offline sasmit  India
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i meant the lm4780
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Old 17th April 2009, 02:50 PM   #17
BrianGT is offline BrianGT  United States
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I received a small batch of boards, and will try them out soon.

LM4780
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Old 17th April 2009, 02:57 PM   #18
BrianGT is offline BrianGT  United States
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LM3886
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Old 17th April 2009, 02:58 PM   #19
Atilla is offline Atilla  Norway
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Great, keep us posted, those boards are looking really nice.
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Old 17th April 2009, 03:11 PM   #20
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by Atilla
Great, keep us posted, those boards are looking really nice.
Thanks! I really miss working on projects, as I have been quite busy with work and car stuff, but am really trying to put more time into building stuff. This should motivate me to get back into building stuff
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