Re: Apple IIGS Stereo Sound Card - Interest?

On 2 Nov, 17:34, "Michael J. Mahon" <mjma...@xxxxxxx> wrote:
Drew wrote:
On 2 Nov, 09:52, "Bill Buckels" <bbuck...@xxxxxxx> wrote:
"Toinet" <> wrote:
Will your board allow sound input as well as sound output? I mean
"numérisation du son" (sound digitization)
Hi Tony,

That would be good if Drew's board provided recording as well as playback
functionality. (i.e. ADC input as well as DAC output).



At the moment it will be output only. I have thought about input, and
i 'might' look at this at a later date. This is all new to me and am
keen to get something produced and then look at how i can improve
things maybe on a version 2.0 board, but to be honest if i was going
to do the input i would need lots of help from the group :).

Since the Ensoniq ADC input (mono) is on the same connector as the
multiplexed outputs, you already have access to the input.

All that's needed is suitable amplification for your intended input
(required for a microphone input) plus an anti-aliasing low-pass
filter--probably another two op-amps as active filters.

The net impact to the bill of materials would be another two
or three op-amps (in one chip), about a dozen passives (resistors
and capacitors), and an input jack--plus a gain control if one is
not available off-card.

If a low-level (microphone) input is provided, some care should
be exercised in laying out the card to avoid noise pickup.


NadaNet 3.0 for Apple II parallel computing!
Home page:

"The wastebasket is our most important design
tool--and it's seriously underused."


I have completed the prototype card (,
but seems the hiss that was on the breadboard is on the real card as
well, specifically on the right speaker. I was wondering if anyone had
some suggestions on a good starting point? possibly the layout of the
board, but I am not expert on what can cause issues with audio on

Any help would be appreciated :)