Posted By
MMS
on 2023-02-06
13:43:32
 |  Re: Covox Speech Thing - parallel port adapter
Yeah, linearity of the resistance ladder will be killed with the high spread of normal resistors.
You may look for tighter spread 1% resistor types for a much higher price, or a time consuming way to sort out the best 10-20% from a batch with manual measurement (it has its own measurement variation too). I had a classmate who did this.
Metal foil resistors will do the job
https://en.wikipedia.org/wiki/Resistor
Though I did not expect this price :-O
So doing with IC has a much more forecastable sound quality.
But on linearity VS inner calculation to fit to TED volume levels is still better on 8 bit sound ladder than our current method.
With the 4 channel IC you can spare on CPU side a lot of calculations of the 4 channel MODs using 8bit samples.
Very smart. The circuit will do the task without overstressing the CPU.
I remember Pigmy's 3 channel digi player had to switch off the screen to able to play the 4 bit samples (mixing of the three channels plus the conversion of the 4bit digis to fit TED volume output levels). Imagine just sending the raw channel data to user port. What a difference.
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