I have tried to read his code, but without success, because too many variables like "TS" and "DTL" e.g. are not defined. So, I cannot say, whether the delay is actually 25 milliseconds. I doubt it.


Adding a buffer at input of ADC isn't the add of "unnecessary complexity" at all. Driving the input of an ADC by a low ohmic source is standard design practise.

Have a look at figure 5 of datasheet of ADC0804:

http://cache.national.com/ds/DC/ADC0801.pdf

and you will see, that at input of ADC a fast switching takes place. This causes noise and the involved loop area of this noise current should be kept as minimal as possible, just what a buffer, mounted near the ADC guarantees.

Again, up to now, we have no idea, why Chico has problems and best procedure at this moment is to check, whether standard design practise is fullfilled. And I doubt this.

Read chapter 2.3.4 about "noise" of same datasheet and you will see, that wires connected to input should be kept as short as possible. Chico is designing a midicontrol, where the two 10k pots can be mounted in a relevant distance to ADC. Here again buffers would help, which Chico is omitting.

An ADC can behave very strange, when violating standard design practise, and things become intermixed, which should not have any influence on each other. For instance, the reason, why Chico has no success, when reducing the delay, can be the result of noise, which is only then present, but not at a later time (think of the Midi data transmission, for instance). Noise which cannot be supressed at all, because buffers are omitted...


Yes, if you take the cheapest. But even with the cheapest you can succeed, if you select a handful for lowest offset.


Read his "Active Filter Cookbook", which is just on my desk, to see, how "simply elegant" his filters are...

Kai