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1U Noise Tools S&H inaccurate pitch sampling


#1

When sampling pitch CV the tuning is slightly off.
Any idea why?
Is my module broken or might I be doing something wrong?

The Doepfer A-148 samples the pitch correctly, so I assume something’s not quite right with th s&h on the Noise Tools.

Or is this the scenario described in the Shifty manual where the pitch is being sampled a bit too early and a gate delay function would be needed (as exists on Shifty)?

Here‘s the explanation from Shifty‘s manual:

Sampling Delay Compensation
Due to the nature of how many Eurorack sequencers or MIDI interfaces are implemented their
CV output can lag their gate output by up to a few milliseconds. The consequence is that if a
module like Shifty samples its CV input immediately upon receiving a gate it may read a value
that is slightly higher or lower than that which the sequencer is outputting. If this CV is
being used to control the frequency of an oscillator it will result in it sounding out of tune.
In the case of Shifty if the module is being used in track & hold mode mode this is rarely a
problem because this behaviour will simply result in a short and usually inaudible pitch glide at
the beginning of the note. However in sample & hold mode if the CV is sampled too early, the
note will be slightly out of tune.
Fortunately Shifty provides a way to compensation for this via a configurable gate delay. With
the gate delay disabled the CV output for the selected voice will reflect the CV input as soon as
possible. With the gate delay enabled the CV output and its corresponding gate will have a
slight delay before updating. This allows the incoming CV to settle at its target value.


#2

I delayed the sample trigger through Maths, but the sampled pitch (or rather its output) is always a bit too low.


#3

Analog S&H suffers from “droop” as explained in this thread on Muffs.

https://www.muffwiggler.com/forum/viewtopic.php?t=66111&sid=3803bf098a2dda3695f4424831cfbdb6

Dr E&S weighs in and tells us how to build an Analog S&H that droops very little, but I’m not sure if he was involved in the Noise tools, or whether those practices were followed.