My requirements are roughly:
As many Hiwatt genes as possible, including layout and dress, which means:
- Front to back circuit flow like the 70's era DR504s
- Running wires as rectilinearly as possible, bundling them like Harry Joyce.
- Fixed bias power section and fixed bias Long Tailed Pair (LTP) phase inverter.
- Clean and loud class AB power section that breaks up only at high volumes.
- Two channels, "Brilliant" and "Normal"
- 70's era tone stack and presence control.
Other design features:
- Single input, with isolated and blended channel switching.
- Switchable pre-amp overdrive.
- EL84 power tubes.
- Elevated DC reference for filament heaters to reduce noise.
- Line out and safety load for use without speaker plugged in.
- Adjustable power tube biasing and exterior test points.
So, I'll make my layout as close to Mark Huss' 70's clone as possible, while accommodating my own additional requirements.
Here are some early sketches and process pics of my attempt at doing that:
