At the chips input after your coupling cap do you have the 1K input resistor and 22K shunt to ground? The 22K resistor offsets the offset created by the 22K NFB . also are you using a cap in your NFB? If you have no feed back caps and no 22K input offset being parallel you would easily see that value offset.
Could you measure the voltages from pins 7 and 25 and post them? Or else the voltages over Rout1 and Rout2?
Do you have the possibility to feed a constant signal into your amplifier for measurements? E. g. with a test CD with sinus signals, a function generator or an old model train transformer?
Best thing would be a signal in the range of 50 to 100 Hz. The multimeter must be set to AC for this measurement of course.
If you can, set the volume to a value, where the protection does not kick in. Then make the same measurements again plus the output voltage at the speaker terminals, and let us have a look at the results.
Did you check the temperature at the chip and the heat sink, when the protection kicks in?
Do you have the possibility to feed a constant signal into your amplifier for measurements? E. g. with a test CD with sinus signals, a function generator or an old model train transformer?
Best thing would be a signal in the range of 50 to 100 Hz. The multimeter must be set to AC for this measurement of course.
If you can, set the volume to a value, where the protection does not kick in. Then make the same measurements again plus the output voltage at the speaker terminals, and let us have a look at the results.
Did you check the temperature at the chip and the heat sink, when the protection kicks in?
Sorry mistype 
Cin is 2.4uF + 220ohm (on signal) + 22K (signal to ground)
I read on forum it's possible to had Ci to help dc offset ?
PS. with this chip it's important for DC OFFSET to have same impedance at input and output ? because on chip input impedance is 22K at the output I have 10K, because I'm in parallel channel-A and channel-B 22K//22K = 11K ?
thanks !
nicK
Cin is 2.4uF + 220ohm (on signal) + 22K (signal to ground)
I read on forum it's possible to had Ci to help dc offset ?
PS. with this chip it's important for DC OFFSET to have same impedance at input and output ? because on chip input impedance is 22K at the output I have 10K, because I'm in parallel channel-A and channel-B 22K//22K = 11K ?
thanks !
nicK
!Nickthevoice,
This is a suggestion, and not meant to be a criticism of your project.
I have a PCB for building a LM4780 to give me dual LM3886 in a chipamp. I realise that eventhough the power ouput is double I still have the problem of die size of the LM4780 is essentially half of LM3886, hence peak current delivery is reduced. I don't think you will get the bass slam compared to discrete components amplifier of SIMILAR power ratings.
I like to suggest to you go for 2 pairs of 2SC5200&2SA1943 per channel with say <75VDC supply, this will give you at least 130Watts. You don't have to build from scratch, there are people selling LME49810 chipset that will drive the above discrete transistors or mosfet, take your fancy. This option is by far superior to the LM4780 option. If you are interested, do a search on LME49810 and Monkey.
I bought a chipset from Monkey and currently building it(I use a single pair/channel, that gives me about 100W, suffcient for me)
This is a suggestion, and not meant to be a criticism of your project.
I have a PCB for building a LM4780 to give me dual LM3886 in a chipamp. I realise that eventhough the power ouput is double I still have the problem of die size of the LM4780 is essentially half of LM3886, hence peak current delivery is reduced. I don't think you will get the bass slam compared to discrete components amplifier of SIMILAR power ratings.
I like to suggest to you go for 2 pairs of 2SC5200&2SA1943 per channel with say <75VDC supply, this will give you at least 130Watts. You don't have to build from scratch, there are people selling LME49810 chipset that will drive the above discrete transistors or mosfet, take your fancy. This option is by far superior to the LM4780 option. If you are interested, do a search on LME49810 and Monkey.
I bought a chipset from Monkey and currently building it(I use a single pair/channel, that gives me about 100W, suffcient for me)
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