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Sample and Hold, Track and Hold, audio rate patches
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author Sample and Hold, Track and Hold, audio rate patches
microfauna
Sample and Hold, Track and Hold, audio rate patches

The following patches use Sample and Hold or Track and Hold to create sample rate modulation, creating digital type sounds from analogue sources. The patches use a 2 VCOs, one as the audio source (VCO1) and the other (VCO2) to clock the S&H or T&H.

Ideally VCO2 should have a square output with pwm and a sync input.
With both patches try with or without sync for harmonic or inharmonic sounds.
If you’re using a 1v/oct control mult it to both VCOs if you want to have a fixed frequency ratio between them.
Try modulating VCO2.
These patches sound great filtered/LPGd.

S&H patch
This is straight ahead sample rate control.
Start with VCO2 at a higher frequency than VCO1

VCO1 tri > S&H in
(VCO1 squ > VCO2 sync in)
VCO2 squ > S&H trig in
S&H out = audio out


T&H patch
This has the effect of hybrid analogue (continuous) and digital (stepped) sound.
Start with VCO2 at a higher frequency than VCO1.
By varying the pwm of VCO2 the ratio of continous source (Track) and stepped samples (Hold) is controlled.

VCO1 tri > T&H in
(VCO1 squ > VCO2 sync in)
VCO2 squ (with pwm)> T&H trig in
T&H out = audio out
microfauna
T&H waveshaping tri to trapezoid patch

This is a patch using a T&H to get a VCO to self waveshape the tri to flatten the top and bottom of the wave to create trapezoid type shapes. It works really well with the sine as well, gradually increasing harmonic content. You could use an LFO instead.
You will need a rectifier, comparator, VCA (ideally with greater than unity gain) as well.

VCO tri > rectifier > inverter > comparator in
set the comparator threshold to a –ve voltage just below the lowest value of the VCO ie without a cv varying the threshold the comparator out is constantly high.
VCO tri > T&H in
comparator out > T&H trig in
T&H out > VCA in
VCA out = waveshaped signal
+ve modulation source > comparator in, VCA cv in
set the bias on the VCA up a bit ie some signal passed without any cv in.

The unmodulated comparator is high, so the T&H is tracking ie the tri is passed unshaped. As the +ve modulation source is increased the point at which the top and bottom of the tri are held lowered (creating trapezoids) until both top and bottom are held at 0v ie no signal is passed.
The VCA acts as gain compensation. As the top and bottom of the trapezoid gradually gets nearer to 0v it gets quieter, so the VCA increases its amplitude to compensate.
microfauna
Double post
cptnal
Bump Bump!

Why no track 'n' hold love? I've seen many recommendations for wave folders in the "what module should I buy" threads, but nothing about T&H at audio rate as a wave shaping tool. Seems odd when something like the Doepfer A-148 is cheap as chips and only 4hp. hmmm.....
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