Teaching Synthesis with Bullfrog XL - Part 6 : The S&H (Sample and Hold?)
Music
Introduction
Hello! I'm Kingas, a synth DIY enthusiast, and welcome to today's video, which is part six of our series. In this installment, we’ll explore the Sample and Hold module, one of my favorite components for creating unique and experimental sounds.
We have already discussed various modules such as the VCO (Voltage-Controlled Oscillator), VCF (Voltage-Controlled Filter), VCA (Voltage-Controlled Amplifier), and Envelope Generators. Now, let's dive into Sample and Hold, a fantastic tool for generating random sequences and stepped modulation signals.
What is Sample and Hold?
As the name suggests, Sample and Hold (S&H) samples and holds input voltages based on a clock signal. The S&H module typically features two main inputs: a clock input (which provides a pulse signal) and a voltage input (from a varying source, like an LFO or noise).
Here's how it works: with each clock pulse it receives, the module takes a snapshot of the voltage at the input. It holds that voltage steady until the next clock pulse, effectively creating a "frozen" output based on the sampled input voltage.
Creating a Random Sequence Patch
In this video, we’ll create a patch that mimics the iconic computer sounds of classic science fiction movies. To get started, you can use the built-in clock from the S&H, which has a pulse output. This pulse will trigger two envelope generators.
Next, connect the output of the VCF (filter) to the audio input of the VCA (amplifier). We will use the first envelope generator to modulate the filter and the second envelope generator to control the VCA.
To generate a varying voltage, we can send the output of our first envelope generator (set in loop mode to act as an LFO) into the S&H. This way, we create a stepped output based on the varying voltage.
Now, we can listen to the sound generated by our sequencer, and as we adjust the rate knob, the output will vary, creating a range of pitched sounds reminiscent of computer noises.
Advanced Techniques
Beyond simple random sequences, you can use S&H for other applications, such as tracking and holding voltage from continuous controllers like ribbon controllers or joysticks. When these controllers are released, the Sample and Hold can hold the last voltage, giving the player control over pitch or filter cutoff even after letting go of the control.
Additionally, the S&H has a manual gate input, allowing you to manually trigger the output voltage instead of relying completely on the internal clock. This provides you with more flexibility in performance.
Generating Interesting Sounds with White Noise
Instead of using an LFO as the voltage source, my preferred method is to use white noise. By connecting the noise output to the S&H, you obtain a random sequence output that can control the frequency of an oscillator. This can produce sounds characteristic of R2-D2 or spaceship computers.
You can also use white noise to create a high-hat-like sound by routing it through a filter and VCA while applying random voltage variations to their parameters. This method produces rhythmic patterns answering our need for variation and unpredictability in sound design.
Conclusion
In this article, we discussed the Sample and Hold module, its functionality, and how to construct patches to generate random sequences and unique soundscapes.
Stay tuned for the next installment of our synthesis journey, where we explore utilities in sound synthesis.
Keywords
- Sample and Hold
- S&H Module
- Random Sequences
- VCO
- VCF
- VCA
- Envelope Generators
- White Noise
- LFO
- Clock Signal
FAQ
Q: What is a Sample and Hold module used for?
A: The Sample and Hold module is used to sample and hold input voltages at each clock pulse, allowing for the generation of random sequences and stepped modulation signals.
Q: Can I use white noise with Sample and Hold?
A: Yes! Using white noise as the input to Sample and Hold can produce random sequences and sounds reminiscent of classic sci-fi computer noises.
Q: How do I trigger the Sample and Hold module?
A: The Sample and Hold module can be triggered using a clock signal. Additionally, it has a manual gate input that allows for external triggering.
Q: Can I use Sample and Hold for purposes other than pitch modulation?
A: Absolutely! Sample and Hold can also be used to modulate filter cutoff frequencies and other parameters by holding a random voltage output.
Q: What is the significance of the envelope generator in the patch?
A: The envelope generators shape the dynamics of the sound by controlling parameters like filter cutoff and amplitude, which can be modulated by the Sample and Hold output.