Re: Apple IIGS Stereo Sound Card - Interest?

[Drew <goggledrew@gmail.com>]

On 2 Nov, 17:34, "Michael J. Mahon" <mjma...@aol.com> wrote:
> Drew wrote:
> > On 2 Nov, 09:52, "Bill Buckels" <bbuck...@mts.net> wrote:
> >> "Toinet" <antoine.vig...@laposte.net> 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).
>
> >> Bill
>
> > Hi,
>
> > 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.
>
> -michael
>
> NadaNet 3.0 for Apple II parallel computing!
> Home page:  http://home.comcast.net/~mjmahon/
>
> "The wastebasket is our most important design
> tool--and it's seriously underused."

Hi,

I have completed the prototype card (http://drewbiegs.blogspot.com),
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
PCB...

Any help would be appreciated :)

Drew