Hi folks,
I've bought e speaker protection board from eBay for my new LM3886 amp build. I have seen various versions of the same circuit with the power supply terminals marked as either 12V AC or DC.
Mine happens to be labelled as DC. I've attached a picture. I had planned to use AC and add a winding to my toroidal to give me 12V. Does this board need to be DC - if so, can I just use a bridge rectifier?
Also, The speaker return connects to ground - I would have thought that would be a bad thing if I'm using AC.
Cheers,
Jon
I've bought e speaker protection board from eBay for my new LM3886 amp build. I have seen various versions of the same circuit with the power supply terminals marked as either 12V AC or DC.
Mine happens to be labelled as DC. I've attached a picture. I had planned to use AC and add a winding to my toroidal to give me 12V. Does this board need to be DC - if so, can I just use a bridge rectifier?
Also, The speaker return connects to ground - I would have thought that would be a bad thing if I'm using AC.
Cheers,
Jon
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Jon,
That circuit needs a smooth DC supply. Therefore needs a bridge rectifier plus a large smoothing capacitor.
Speaker Return is GND and the protection circuit 0 volt needs to connect to that GND at that point only (so that it measures accurately without hum and other induced noise).
However Spkr Ret for each channel is normally kept separate until they reach the power amp board, again to minimise noise and ground loops. It is a poor design in your board, but it might be OK.
That circuit needs a smooth DC supply. Therefore needs a bridge rectifier plus a large smoothing capacitor.
Speaker Return is GND and the protection circuit 0 volt needs to connect to that GND at that point only (so that it measures accurately without hum and other induced noise).
However Spkr Ret for each channel is normally kept separate until they reach the power amp board, again to minimise noise and ground loops. It is a poor design in your board, but it might be OK.
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