If you are looking at a circuit diagram, focus on these areas:
Even when unplugged, large capacitors can hold a high-voltage charge.
The 12AX7 requires a specific filament voltage (usually 6.3V or 12.6V). If your pedal isn't lighting up or passing signal, this is the first place to check for a blown component. ⚠️ A Critical Warning The HT-Dual is not a beginner project for DIY repair. Lethal Voltages: The internal 300V rail can be fatal.
Troubleshooting the switching power supply requires an oscilloscope and advanced knowledge of high-frequency electronics. If you'd like to dive deeper, let me know: Are you trying to repair a broken unit?
Both halves of the tube are utilized. One half typically handles the initial gain stage, while the second provides additional clipping and drive.
Blackstar’s proprietary "Infinite Shape Feature." On the schematic, this looks like a specialized tone stack that shifts the center frequency and response between "American" (tighter, scooped) and "British" (woodier, mid-forward) voicings. 🛠️ Key Schematic Sections to Study