Hi techies,
I just obtained a Jackie Chan arcade PCB, and the only available sound options are amplified speaker +/- (and audio ground) via the jamma harness or amplified stereo (L/R + and -) via a pin header. See http://www.arcade-museum.com/manuals-videogames/J/Jackie_Chan_In_Fists_Of_Fire_Operation_Manual.pdf
I know enough about electronics and amps to have basic familiarity, but not enough to really understand the complexities.
As far as I can see (and with help from https://github.com/mamedev/mame/blob/master/src/mame/drivers/jchan.cpp), there's a TA8210 2-channel power amplifier connected to these amplified audio outputs (makes sense), with inputs that trace back to a trim pot, whose inputs in turn go through some resistor/capacitor networks back to a C4741C differential input quad op-amp. Of course the op-amp outputs feed back into the inputs, so there's all of that.
The block diagram of the TA8210 in the datasheet below matches pretty much perfectly the implementation as I've probed around it:
http://pdf1.alldatasheet.com/datasheet-pdf/view/31449/TOSHIBA/TA8210.html
But due to the presence of the trimpot, I'm not quite sure whether the inputs to the power amp are considered ''line level" - or whether that needs to be taken from before the trimpot and somewhere in between it and the op-amp (and capacitor/resistor madness). Unfortunately there's not a useful block diagram of reference implementation around the C4741C.
http://pdf1.alldatasheet.com/datasheet-pdf/view/12099/ONSEMI/MC4741CD.html
Any help appreciated. I can try to work out more of the cap/res madness around the C4741C if that's useful.
If the answer is just 'take line level from straight after (or before) the trim pot' then that's excellent
I just obtained a Jackie Chan arcade PCB, and the only available sound options are amplified speaker +/- (and audio ground) via the jamma harness or amplified stereo (L/R + and -) via a pin header. See http://www.arcade-museum.com/manuals-videogames/J/Jackie_Chan_In_Fists_Of_Fire_Operation_Manual.pdf
I know enough about electronics and amps to have basic familiarity, but not enough to really understand the complexities.
As far as I can see (and with help from https://github.com/mamedev/mame/blob/master/src/mame/drivers/jchan.cpp), there's a TA8210 2-channel power amplifier connected to these amplified audio outputs (makes sense), with inputs that trace back to a trim pot, whose inputs in turn go through some resistor/capacitor networks back to a C4741C differential input quad op-amp. Of course the op-amp outputs feed back into the inputs, so there's all of that.
The block diagram of the TA8210 in the datasheet below matches pretty much perfectly the implementation as I've probed around it:
http://pdf1.alldatasheet.com/datasheet-pdf/view/31449/TOSHIBA/TA8210.html
But due to the presence of the trimpot, I'm not quite sure whether the inputs to the power amp are considered ''line level" - or whether that needs to be taken from before the trimpot and somewhere in between it and the op-amp (and capacitor/resistor madness). Unfortunately there's not a useful block diagram of reference implementation around the C4741C.
http://pdf1.alldatasheet.com/datasheet-pdf/view/12099/ONSEMI/MC4741CD.html
Any help appreciated. I can try to work out more of the cap/res madness around the C4741C if that's useful.
If the answer is just 'take line level from straight after (or before) the trim pot' then that's excellent
