Dedicated Constant-Impedance Attenuator Network
The attenuator circuit is built as a separate, dedicated network using Ohmite chassis-mount wirewound resistors, including HS10 and HS25 series parts rated from 10W up to 25W. These resistors are intentionally over-specified to provide substantial thermal headroom, stable impedance at every attenuation step, and long-term reliability under continuous power dissipation. By isolating the attenuator electrically and thermally from the main amp board, heat and load variation are kept out of the signal path and power supply.
Low-Noise, Precision Signal Path
Critical signal-path resistors throughout the amplifier use Vishay and Yageo metal film resistors, selected for their low noise characteristics, tight tolerances, and long-term value stability. This minimizes hiss, maintains consistent gain structure from amp to amp, and ensures predictable response across the entire preamp and phase inverter stages.
High-Quality Film and Electrolytic Capacitors
Tone-shaping and coupling duties are handled by Mallory 150 series film capacitors and Vishay film capacitors, chosen for smooth frequency response, low dielectric absorption, and proven musical performance in tube circuits. Power supply filtering relies on F&T electrolytic capacitors, known for low ESR, strong ripple handling, and long service life, contributing to a stable, articulate power section without harshness.
Silver Mica for Precision High-Frequency Control
Where accuracy matters most—such as high-frequency shaping and stability points—the circuit employs CDE silver mica capacitors. These components offer excellent temperature stability and tight tolerance control, ensuring consistent treble response and predictable behavior even at high signal levels.
Robust Hardware, Controls, and Interconnects
All tube sockets are Belton chassis-mount sockets, including Micalex 9-pin sockets with shielding where required, selected for mechanical stability and resistance to heat-related drift. Input and output connections use Switchcraft jacks, while switching duties are handled by Carling toggle switches and Alpha rotary switches for consistent feel and long-term reliability. The primary user controls — Normal Volume, Bright Volume, Bass, and Treble — use custom-spec Bourns potentiometers, chosen for smooth taper, tight tolerance, and durability under constant adjustment.
Mechanical Design and Thermal Management
The amplifier chassis is fabricated from .068” thick 308 stainless steel, providing exceptional rigidity, corrosion resistance, and long-term structural stability under heat. The attenuator network is housed in its own dedicated aluminum enclosure, allowing efficient heat dissipation while isolating thermal load from the main amplifier electronics. Chassis-mounted power components are thermally managed using silicone-free thermal interface compound, improving heat transfer without outgassing or long-term breakdown.
Built for Serviceability and Longevity
Thoughtful component spacing, conservative power ratings, chassis-mounted heat-generating parts, and panel-mounted service components result in an amplifier that is stable, maintainable, and built for decades of real-world use. Every design choice prioritizes reliability, consistency, and sonic integrity—not just initial performance, but performance that lasts.