Overview
The Megatron XL is a fully tube-based, two-chassis electrostatic headphone amplifier developed by Kevin Gilmore as an evolution of the original Megatron design.
While the original Megatron employs four EL34 / 6CA7 tubes in the output stage, the Megatron XL takes the design further by upgrading the output stage to four directly heated 300B triodes. This change introduces the characteristic qualities of the 300B tube—a natural tonal density, refined micro-detail, and an organic presentation—while maintaining the high-voltage stability required for electrostatic headphones.
The complete amplifier uses a total of twelve vacuum tubes:
2 × ECC82
2 × ECC83
4 × EL34 / 6CA7
4 × 300B
This architecture provides substantial flexibility for tube rolling, allowing users to fine-tune the sound character to their preference.
Megatron XL Power Supply & Protection Design
The Megatron XL features a carefully engineered power supply system designed for long-term reliability and component protection.
Three independent Golden Reference High Voltage (GRHV) power supplies are used for the high-voltage sections.
The 15V low-voltage supply also employs a Golden Reference design, rather than conventional LM78xx / LM79xx regulators.
Integrated protection and control modules include:
Power-on inrush current suppression
Short-circuit current limiting
High-voltage delayed soft-start (~40 seconds)
Dedicated soft-start filament supply for the 300B tubes
These measures significantly extend the lifespan of the amplifier, tubes, and connected headphones.
The internal 300B filament supply includes a selectable configuration, allowing future replacement of the 300B with 2A3 tubes, providing an upgrade path without major hardware changes.
Photos
Megatron XL Technical Specifications
- Fully tube-based dual-chassis electrostatic headphone amplifier
- Tube complement: 2 × ECC82, 2 × ECC83, 4 × EL34 / 6CA7, 4 × 300B
- Output: Stax Pro Bias (580V) + Optional Normal Bias output
- Power-on inrush protection
- Short-circuit current limiting
- High-voltage delayed start (~40 seconds)
- Soft-start, switchable 300B filament power supply
- Independent filament modules for each 300B tube (4 total)
Customization Options
- Optional Normal Bias output jack
- Tube selection (subject to availability)
- Volume potentiometer upgrade to TKD (Alps as standard)
- Power supply tuning for regional mains voltage
What’s Included
- Amplifier chassis and external power supply chassis
- Aviation-grade power connection cables
- Tube set (configuration dependent)
Pricing & Lead Time
- Price: Quoted based on configuration
- Lead Time: Typically 3 months after confirmation
Ordering Information
Please contact me via email below.
📧 Email: xianghao9506@gmail.com