Hi, does anybody use this PCB for LM3886. I'm going to build 2 parallel/pcb. PCB it self for stereo and thickness of pcb 2.6mm.
Just wonder if I can use same componen value as it's printed. And input line are + and - instead L and R. The + and - goes to same pin number, so I conclude it is not bridge.
Just wonder if I can use same componen value as it's printed. And input line are + and - instead L and R. The + and - goes to same pin number, so I conclude it is not bridge.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
The black paint is very perfect to hide some copper track even scanner can't "see" it . I draw the scheme and use multimeter to trace connection of some point and get this:
(Sorry the R18K and C 1uf is connected to pin no 8 not to output)
I build one channel w/ 30 volt+/-DC and result is good, eventhough I do not put the C = 1 uf.
(Sorry the R18K and C 1uf is connected to pin no 8 not to output)
I build one channel w/ 30 volt+/-DC and result is good, eventhough I do not put the C = 1 uf.
Last edited:
biased R=4.7k what does that refer to?
Link to a schematic and use the schematic component labeling to make clear what you are talking about.
Andrew T,
Sorry . Actually I'm refer to the 4.7K in my drawing scheme.
Also I wonder is the elco =1uf is really needed ?
Upload again the scheme :
An externally hosted image should be here but it was not working when we last tested it.
that schematic is visible for me
It's slightly unusual with such high input impedance and feedback resistor. I can't think of any good reason to do that rather than use the more usual 22K. Still, if it works and sounds good, it's OK
The input coupling capacitor, it depends on your source. If it has a low DC offset to start with, you can get away with it. Personally I would also like to have an input lowpass filter for RF rejection.
It's slightly unusual with such high input impedance and feedback resistor. I can't think of any good reason to do that rather than use the more usual 22K. Still, if it works and sounds good, it's OK
The input coupling capacitor, it depends on your source. If it has a low DC offset to start with, you can get away with it. Personally I would also like to have an input lowpass filter for RF rejection.
He has uploaded it again, here is the link http://i885.photobucket.com/albums/ac60/yd1cvj/IMG02073-20121025-1718.jpg
No idea why doesn't it work for you, AndrewT.
Regards, Vic.
No idea why doesn't it work for you, AndrewT.
Regards, Vic.
To balance the two inputs, the FB resistor (at -in) will usually be equal to the other resistor (at +in). The resistor at +in is connected to ground. The higher the resistance, the better the noise floor, as can be seen in simulators.
Beside lifting the input impedance, it is often mentioned in "Design Example" of a chip datasheet to use such a high resistance (usually mentioned as 100k) to lower output offset.
I have tested many resistance and the offset differences are not big. Even the lowest offset was not the best sound to my ears.
But with FB resistance as high as 100k you can get away with 4u7 MKP in the FB path. May be it is audible if compared with low quality electrolytic? (mine was BG, so no worse)
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.