Whohoho Edits.. Many Thanks! 
Now.. I'm still trying hard to remember who was sitting next to me during the Blind Test..
Also tried hard to remember who was the juror for that event..
But, I got to admit that it was fun for me to be able to participate in that blind test... truly a memorable experience.. especially for me.. a newbie DIY
Now.. I'm still trying hard to remember who was sitting next to me during the Blind Test..
Also tried hard to remember who was the juror for that event..
But, I got to admit that it was fun for me to be able to participate in that blind test... truly a memorable experience.. especially for me.. a newbie DIY
Hi guys, i build this schematic, test it and dont work no sound at the output, just an HUMMM.
Can someone please check if everything are OK?
http://www.proyectosdiy.com/_tmp/sch2.pdf
Thanks in advance.
no sound at the output, just an HUMMM.Can someone please check if everything are OK?
http://www.proyectosdiy.com/_tmp/sch2.pdf
Thanks in advance.
Hola, Samsagaz.
The schematic shows all GND connections to have the same potential. Maybe you have produced a ground loop somewhere. Many threads in this forum deal with separate grounding for signal and power, and with star grounding concepts. If you cannot find your solution there, please post photos and/or your PCB layout.
Do you get hum with anything connected to the input? Or with the input floating? Or shorted?
Does the hum go away, if you lift GND from PE?
Do you support C2 and C3 with more capacitors outside the PCB? Or do you really only use 220µF per rail?
The schematic shows all GND connections to have the same potential. Maybe you have produced a ground loop somewhere. Many threads in this forum deal with separate grounding for signal and power, and with star grounding concepts. If you cannot find your solution there, please post photos and/or your PCB layout.
Do you get hum with anything connected to the input? Or with the input floating? Or shorted?
Does the hum go away, if you lift GND from PE?
Do you support C2 and C3 with more capacitors outside the PCB? Or do you really only use 220µF per rail?
I get the HUM with any input, if i get it floating no HUM.
im using just 220uf per rail, the Power Supply have like 30000uf
this is the PCB Design.
http://www.proyectosdiy.com/_tmp/pcb.pdf
im using just 220uf per rail, the Power Supply have like 30000uf
this is the PCB Design.
http://www.proyectosdiy.com/_tmp/pcb.pdf
As far as I understand your PCB you have put the star grounding point on the PCB at the bottom of your drawing (bigger drilling), is that right?
The ground plane forms a closed loop around the PCB. You could try to interrupt it somewhere, e. g. behind the chip. At the moment you have two paths from the ground connection to Ri. A short path over the right side, and a long path over the left side running on the top over the chip to the right and then down again. You might get the hum from there.
You can check that before cutting the PCB. Lift Ri or Ci, which ever you have connected there, from the ground below IC pin 11, where it seems to be connected now, and connect Ri/Ci directly to the star point with a wire. Make sure the wire doesn't connect to the ground anywhere else. If the hum goes away, you need to cut the loop as I wrote above.
If the hum doesn't go away, you may still cut the loop and it will probably help, but then there might be some further cause for the hum.
The ground plane forms a closed loop around the PCB. You could try to interrupt it somewhere, e. g. behind the chip. At the moment you have two paths from the ground connection to Ri. A short path over the right side, and a long path over the left side running on the top over the chip to the right and then down again. You might get the hum from there.
You can check that before cutting the PCB. Lift Ri or Ci, which ever you have connected there, from the ground below IC pin 11, where it seems to be connected now, and connect Ri/Ci directly to the star point with a wire. Make sure the wire doesn't connect to the ground anywhere else. If the hum goes away, you need to cut the loop as I wrote above.
If the hum doesn't go away, you may still cut the loop and it will probably help, but then there might be some further cause for the hum.
samsagaz said:
If the hum is not present with the input floating then there is a ground loop with your source through safety earth. Try feeding it with an ipod/mp3 player (of course not connected to a computer by usb) and check there is no hum with the ipod paused (if it's switched off the output becomes high-impedance and acts like an antenna.
Puffin said:
This PCB are from Top. the schematic show that Pin3 are connected to pin 9, not 10. and in the PCB are connected to Pin 9, not 10.
pacificblue said:
The ground is the big Hole at bottom like you say. So you say that is not good to use an full plane gnd, right? will be better to cut the PCB to separate the Gnd?
i will try what you say.
Btw the HUM that i get are without sound, just HUM, no input.
Btw, i dont have anything connected to Pin 11 right now :S in the datasheet i found that Pin11 are NC.
ionomolo said:
i thinked that the PCB are wrong, but if noone noticed anything strange, so will try to play with the GNDs, to see if can improve it.
It is a matter of taste, if you prefer planes or not. The important thing is that you don't produce a closed loop. You don't need to separate the grounds, only break the loop. A small slit somewhere is sufficient to do that. Behind the IC seems to be the best place for that.
You can of course separate the grounds entirely, if you like. But that would mean a total redesign for your PCB. Then you would probably not be working with planes any more, but with two star-shaped grounds.
Planes have their advantages as well. They reduce resistances, take higher currents and improve cooling (the last very little, but still), and somethimes even provide a kind of shielding. So a small cut through the path on top of the IC should be sufficient. But try first by lifting Ri/Ci from the current ground connection to the star point, if that is already the solution. Ionomolo has a point, if the hum goes away with the input floating, there is a loop with the source.
Pin 11 is NC. You can connect it wherever you like or leave it floating like you do now.
You can of course separate the grounds entirely, if you like. But that would mean a total redesign for your PCB. Then you would probably not be working with planes any more, but with two star-shaped grounds.
Planes have their advantages as well. They reduce resistances, take higher currents and improve cooling (the last very little, but still), and somethimes even provide a kind of shielding. So a small cut through the path on top of the IC should be sufficient. But try first by lifting Ri/Ci from the current ground connection to the star point, if that is already the solution. Ionomolo has a point, if the hum goes away with the input floating, there is a loop with the source.
Pin 11 is NC. You can connect it wherever you like or leave it floating like you do now.
i made a new PCB
http://www.proyectosdiy.com/_tmp/pcb2.pdf
http://www.proyectosdiy.com/_tmp/pcb-names.pdf
a little small than the other
but will dont work, because are the same components than the other pcb
http://www.proyectosdiy.com/_tmp/pcb2.pdf
http://www.proyectosdiy.com/_tmp/pcb-names.pdf
a little small than the other
but will dont work, because are the same components than the other pcb
Do you only have one PCB or do you have two (for stereo)? If you have two, are both humming? Does the hum still go away, when you have nothing connected to the input?
The strange thing is that the hum is so strong, you don't even get a music signal. Sounds like you have a feedback loop from output to input that you interrupt, when nothing is connected to the input.
Although it is somehow a good sign, because it shows that the IC is still working. A broken IC has either only DC at the output or nothing at all.
Back to the loop. Are your input and output connectors mounted in the amp case already? And are they isolated from it?
I once had a similar behaviour, loud hum and no music, when I had a bad connection from Ri/Ci to ground (R2/C1 in your drawing). Maybe you can check that, too.
The strange thing is that the hum is so strong, you don't even get a music signal. Sounds like you have a feedback loop from output to input that you interrupt, when nothing is connected to the input.
Although it is somehow a good sign, because it shows that the IC is still working. A broken IC has either only DC at the output or nothing at all.
Back to the loop. Are your input and output connectors mounted in the amp case already? And are they isolated from it?
I once had a similar behaviour, loud hum and no music, when I had a bad connection from Ri/Ci to ground (R2/C1 in your drawing). Maybe you can check that, too.
i have just one PCB; i will made a few now, just to test if the IC are wrong, the output of the amplifier are always DC, if i turn on the vol of my Pre, i get the same RMS value no increased the volts
will made this new board and will check it something are wrong...
what happend if i change the Ci capacitor? its not an electrolytic one, right? i tryed with an 0.22uf cap and still getting the same problem.
no increased the volts will made this new board and will check it something are wrong...
what happend if i change the Ci capacitor? its not an electrolytic one, right? i tryed with an 0.22uf cap and still getting the same problem.
Ci is most probably an electrolitc capacitor, because better capacitor types are very big and expensive at 22µF. You can use different values for Ci, and have to find your best compromise. The bigger Ci, the lower the bottom roll-off frequency. 0.22µF is not a practical value, it should be 22µF or bigger. With 0.22µF and 1k you get a lower-3dB at 723 Hz. (fc=1/(2xPixRixCi)
So you have DC at the output? How much? And do you also have DC at the input?
Is the humming accompanied by a clicking sound like very fast switching noise? Then you hear the spike protection system trying to protect the IC. Can you put any capacitor in as Cin (between input and Rb or R1 for you) to see if blocking DC from the input helps? You can use any value for the test. If the test is successful, use 1µF or bigger. Must be good quality, MKS or better.
So you have DC at the output? How much? And do you also have DC at the input?
Is the humming accompanied by a clicking sound like very fast switching noise? Then you hear the spike protection system trying to protect the IC. Can you put any capacitor in as Cin (between input and Rb or R1 for you) to see if blocking DC from the input helps? You can use any value for the test. If the test is successful, use 1µF or bigger. Must be good quality, MKS or better.
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