Apple IIgs "old Apple sound" mods

[ToasterKing]

I have a ROM 3 Apple IIgs with an Applied Engineering Sonic Blaster
card for stereo audio output and input sampling, connected to external
amplified speakers. The Sonic Blaster only processes the digital audio
coming from the J-25 connector on the Ensoniq 5503 DOC and doesn't play
the legacy sounds from 8-bit Apple software. The problem is, if I have
the GS's internal speaker on for those sounds, the internal speaker
also plays the GS sound that comes from my external speakers, but with
a lesser acoustic quality and monophonically.

I want to be able to do one of two things:
1. Modify the GS so that the legacy Apple sound also plays through the
external speakers, and disconnect the internal speaker. I think this
would require some decoupling and possibly an op-amp. I only want to
do this if it won't introduce noise into the external speakers, or
degrade the sound quality.
2. Modify the GS so that ONLY the legacy sound comes from the internal
speaker (and only the Ensoniq output through the external speakers). I
would think this would be as simple as clipping a motherboard trace,
but I don't know which one.

If anyone has pinouts of the Mega II (for old Apple sound output)
and/or the mixing and amplification circuitry for the headphone output
and internal speaker, it would be most appreciated. And otherwise,
does anyone have any tips for me on this?

Thanks,
TK

--
<<Please remove the word "SPLAT" from either below address to use it.>>
Email: mailto:ToasterKing@SPLATbigfoot.com
Visit ToasterKingdom at http://SPLATtoasterking.tripod.com/

 

[Michael Black]

ToasterKing (toasterking@SPLATbigfoot.com) writes:

I have a ROM 3 Apple IIgs with an Applied Engineering Sonic Blaster
card for stereo audio output and input sampling, connected to external
amplified speakers. The Sonic Blaster only processes the digital audio
coming from the J-25 connector on the Ensoniq 5503 DOC and doesn't play
the legacy sounds from 8-bit Apple software. The problem is, if I have
the GS's internal speaker on for those sounds, the internal speaker
also plays the GS sound that comes from my external speakers, but with
a lesser acoustic quality and monophonically.

I want to be able to do one of two things:
1. Modify the GS so that the legacy Apple sound also plays through the
external speakers, and disconnect the internal speaker. I think this
would require some decoupling and possibly an op-amp. I only want to
do this if it won't introduce noise into the external speakers, or
degrade the sound quality.
2. Modify the GS so that ONLY the legacy sound comes from the internal
speaker (and only the Ensoniq output through the external speakers). I
would think this would be as simple as clipping a motherboard trace,
but I don't know which one.

If anyone has pinouts of the Mega II (for old Apple sound output)
and/or the mixing and amplification circuitry for the headphone output
and internal speaker, it would be most appreciated. And otherwise,
does anyone have any tips for me on this?

Thanks,
TK

This isn't a repair issue.

Ask in comp.sys.apple2

Michael