Quartet Lab is a small, independent workshop based in the United States, focused on DIY electrostatic headphone amplifiers.
I began building electrostatic amplifiers around 2013, initially to support fellow enthusiasts who were looking for reliable, carefully built solutions based on well-known designs such as Megatron, T2, KGSSHV Carbon, Grounded Grid, and KGST.
Around 2017, due to a demanding work schedule, I stopped taking external build requests and focused only on building amplifiers for my own use.
In recent years, with more time available again, I have resumed accepting limited build commissions, continuing the same approach I have always followed: careful assembly, thorough testing, and clear communication.
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.
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Grounded Grid
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:
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T2 Mini
Overview The T2 Mini is a modern engineered, compact interpretation of the legendary STAX SRM-T2.
It preserves the core circuit topology and sonic philosophy of the original T2, while significantly improving practicality, manufacturability, and long-term serviceability.
While the original T2 relies on a large number of obsolete and discontinued components, the T2 Mini replaces these parts with modern, readily available equivalents, ensuring that the design can be reliably built, serviced, and supported today.
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