IBX100 sound components - revision A

[Ralph Barrett]

<More discussion of sound circuit>

>>C5, C3 1uF +  += from ESP board
>
>Are you sure? The PCB footprints are small (0805 size), not many 1uF caps
>come in that size and the Philips app note shows 1nF!

Sorry a typo. Should be 1nF. I sketched out the circuit and cannot read
my own writing !

>>R3, R(not marked?) 10k +
>>R6, R(not marked) ?? (these are not fitted on my ESP board)
>
>So that gives us R3 and R5 as 10K and R4 and R6 as unknown. They must be
>small values, probably to match the load impedance of the destination -
>guess 1k or less ? any bigger and the 10k load resistors would start affect
>the level. I'll fit 0R to start with :-).

Your description here is correct, but the schematic has R6 in the wrong
place. R6 is the series resistor. I wonder if the series resistor is
just to provide some sort of short circuit protection for the op-amps ?

I can have another look inside my RiscPC to see if these same series
resistors are fitted. I expect that they are - indeed I expect that the
same people designed the two machines ? Or at the very least the Lazurus
team were able to copy the RiscPC/A7000 designs as necessary.

>>X2 11.2896Mhz +
>Bugger forgot that :-)

I *think* that I've seen 11.2896Mhz crystal oscillators fitted to PC
sound cards. Or get hold of a cheap RiscPC sound card from somewhere and
remove all of the bits you need;-) Note however that I've got two
different RiscPC 16-bit soundcards, and they are quite different.

Ralph

ps Please apply a bit more <snipping> to these posts. To much repeated
verbage IMHO.