Refining the Twin Boost: Hard Clipping and the Benefits of Voltage Regulation

The Twin Boost continues to evolve, and each stage of its development brings fresh challenges and opportunities to learn. In the last few days, I’ve made some key changes to the design, tackling an impedance issue that was throwing the circuit off balance and refining the way the pedal handles power. It’s been another step in shaping the Twin Boost into the pedal it’s meant to be.

The buffer I’d originally designed for a buffered bypass worked beautifully on its own but struggled when paired with the Twin Boost circuits. Even with the addition of 7809 voltage regulators to give the buffer and the boost circuits their own stable 9V supplies, the two didn’t play nicely. The impedance mismatch between the two boost circuits was the source of the problem, and whilst the original plan to include the buffer could have solved the problem, the interaction between grounds of the twin boost and buffer took this solution out of the picture.

Why Hard Clipping Fixed the Impedance Issue

One side of the Twin Boost had hard clipping in its circuit; the other didn’t in this latest revision of the pedal, in an attempt to clean up the tone. This imbalance created an impedance mismatch that caused instability when the two sides interacted. After researching and testing, I decided to return to a hard clipping circuit with two 1N4001 diodes, and it worked exactly as I’d hoped.

Here’s why it worked:

1. Balancing the Output Impedance:
   Hard clipping naturally reduces the output impedance by limiting how the signal interacts with the load. Adding this circuit brought the two sides of the Twin Boost into line, resolving the instability.

2. Controlling Signal Peaks:
   The 1N4001 diodes compress the big peaks in the signal, preventing overload and keeping the circuit stable. Since the 1N4001 diodes have a fairly high forward voltage (~0.7–1V), they only clip the larger peaks, leaving the smaller dynamics untouched. This keeps the compression subtle and avoids colouring the tone too much.

3. Maintaining the Pedal’s Core Tone:
   The hard clipping adds just enough control to smooth out the signal interaction without altering the mostly-clean, characterful boost tone I’ve worked so hard to refine. It’s a satisfying balance of function and sound.

The Role of the 7809 Voltage Regulators

Although the buffer didn’t make it into the final design, I’m leaving the 7809 regulators in place. One of their big advantages is that they allow the pedal to handle higher input voltages, up to 18V or more, while still regulating the output to a stable 9V.

This means the Twin Boost can work with a wider range of power supplies without risking damage to the circuits. Because the regulators bring the voltage down to 9V, the functionality of the circuits stays the same, but the extra flexibility is a nice bonus for players using higher-voltage supplies. It’s one of those behind-the-scenes features that adds robustness without needing to shout about it.

Reverting to True Bypass

With the impedance issue solved, I’ve decided to revert the pedal back to true bypass. While the buffered bypass idea was an interesting experiment, I think true bypass suits the Twin Boost’s design philosophy better. It keeps the signal path simple and avoids introducing unnecessary complexity.

That said, the work I’ve done on the buffer circuit hasn’t gone to waste. The buffer design worked brilliantly when tested as a standalone circuit, and I’m planning to offer it as an option for anyone who might want to incorporate it into their setup. Whether as a custom addition or part of a future project, it’s nice to know the design has potential beyond this one pedal.

What I’ve Learned

This part of the Twin Boost’s development has been a reminder of how every detail in a circuit can have a ripple effect. Adding the hard clipping diodes not only resolved the impedance issue but also made the pedal more stable and predictable overall. Meanwhile, the 7809 regulators have given the design an extra layer of flexibility, making it easier to integrate into different rigs.

What’s exciting about this process is how much it pushes me to understand the circuits I’m working with on a deeper level. From researching impedance matching to testing how components interact, it’s been a real mix of creativity and technical problem-solving. That’s what I love about designing pedals—it’s never just one thing; it’s all the parts working together.

The Twin Boost is getting closer to where I want it to be, and I can’t wait to share more as it comes together. If you’ve been following along, thanks for sticking with me through the ups and downs. As always, I’d love to hear your thoughts or questions—whether it’s about the hard clipping, the voltage regulation, or anything else, feel free to get in touch.

Stay tuned for more updates!