In short: CHUCK runs on 24 volts but generates an internal plate voltage of around 250 volts. This high voltage is needed for the real tube preamp. A built-in high-voltage converter turns the low supply voltage into the required high voltage efficiently. The ~250 volts exist only inside the unit and are not accessible at any jack.
Why does a tube need such a high voltage?
CHUCK runs a real analog tube preamp. An amplifier tube controls the flow of electrons between its electrodes. To operate in its intended range, it needs a much higher plate voltage than ordinary pedals or digital audio devices.
Some compact tube devices run on heavily reduced plate voltages, using either specially suited tubes or adapted circuits. That's common enough, but it changes the tone and response compared with what guitarists know from classic high-voltage tube circuits.
That's why CHUCK provides its tube preamp with around 250 volts, so the tubes can work under conditions that match a classic high-voltage tube preamp.
How do 24 volts become around 250 volts?
CHUCK uses a built-in high-voltage converter that first stores electrical energy in a magnetic field and then releases it at a higher voltage level. Simplified, it works like this:
- An electronic switch pulses the 24-volt supply at high frequency.
- During the on phase, energy is stored in the transformer's magnetic field.
- When it switches off, that energy is released on the secondary side.
- The resulting higher voltage is rectified and smoothed.
- A regulator stabilizes the plate voltage at the intended value.
Does a high voltage also mean high power consumption?
No. Voltage and power are not the same thing. The tube preamp needs a high voltage but only a comparatively small current. That's why CHUCK doesn't need a large power supply like a classic all-tube amp: only the tube preamp runs on high voltage. The built-in 25-watt power amp is far more efficient than a classic tube power amp and needs no large output transformer.
Why isn't a large mains transformer used?
A classic tube amp usually generates its high voltage with a large mains transformer. That works reliably but takes up a lot of space and adds weight. The switched high-voltage converter allows:
- a compact form factor
- a lower weight
- a stable plate voltage
- operation from an external 24-volt power supply
- a real high-voltage tube preamp in floor format
⚠️ Is the high voltage dangerous? The ~250 volts are located exclusively inside the unit. Under normal use you never come into contact with this voltage. Even so, CHUCK must not be opened or repaired yourself. Even after power-off, internal components can still store electrical energy. Servicing and tube changes should therefore only be carried out by suitably qualified specialists.
Key takeaways
- CHUCK is powered externally with 24 volts.
- Internally, a high-voltage converter generates around 250 volts.
- The high voltage feeds the real analog tube preamp.
- The high voltage lets the tubes operate in a classic range.
- The 250 volts are not present at any external jack.
- The unit must not be opened or repaired on your own.