Overview
The Grounded Grid (GG) is a hybrid electrostatic headphone amplifier designed by Kevin Gilmore, combining a solid-state front end with a tube-based output stage.
It is widely regarded as one of the most stable, reliable, and technically elegant electrostatic amplifier designs, offering excellent performance while remaining practical for long-term daily use.
A defining feature of the Grounded Grid topology is that the control grids of the output tubes are directly referenced to ground.
This design choice provides several important advantages:
Absolute DC reference stability
The tube’s operating point is referenced to a fixed and noise-free potential, eliminating long-term drift caused by floating grid bias networks.Reduced susceptibility to offset and noise
A grounded grid greatly reduces sensitivity to leakage currents, grid bias variation, and power-supply-related disturbances, resulting in lower output offset and improved channel stability.Improved linearity and predictability
With the grid held at ground potential, tube behavior becomes more repeatable and consistent across tube samples, which is especially important when using beam tetrodes such as EL34 / 6CA7.
The Grounded Grid uses four EL34 / 6CA7 output tubes, making tube rolling both easy and accessible.
Similar to the T2 and DIY T2 architectures, the output tube plates in the GG are loaded by constant current sources (CCS).
This approach provides major technical benefits:
- Significantly increased voltage swing capability
- A much wider and more linear operating region for the tubes
- Improved distortion performance under real headphone loads
In addition, the GG employs a switchable DC servo–based offset balance system, ensuring that both channels remain centered at optimal operating points over time.
This servo can be enabled or disabled, allowing users to choose between absolute long-term stability or a fully passive signal path.
Overall, the Grounded Grid represents a carefully balanced design—combining tube character, solid-state precision, and long-term reliability—making it an excellent choice for users seeking a reference-level electrostatic amplifier without the complexity of larger all-tube designs.
Technical Specifications
- Hybrid solid-state and tube electrostatic headphone amplifier
- Tube complement: 4 × EL34 / 6CA7
- Output: Stax Pro Bias (580V)
- Constant current source (CCS) plate loading for output tubes
- Grounded grid topology for improved stability and linearity
- Switchable DC servo offset balance system
Customization Options
- Chassis finish: Matte Black or Matte Silver
What’s Included
- Amplifier chassis and external power supply
- Aviation-grade power connection cables
- Tube set (configuration dependent)
Pricing & Lead Time
- Price: $3,499 + shipping
- Lead Time: Typically 1–2 months after confirmation
Contact
Email: xianghao9506@gmail.com