Overdrive Amp (Frost FOD-100)




Inspired by the famous Dumble Overdrive amplifier this is our take on the design. It is a 100W 6L6 design. (Can use EL34 if preferred). We have not modified the signal path design much but have changed the power supply to fit currently available components. We have come up with an innovative bias circuit which makes bias adjustment truly easy. The prototype is nearly finished. We hope to get it pretty right electrically with the prototype. Later versions will tidy up the physical layout.

One of the principal design parameters is that the amp will be long lasting (50 years or more). To this end it features:
• Point to point wiring (hand wired)
• No PCBs, all turret boards
• Aviation grade Teflon wiring
• Selectable output impedance: 4, 8 or 15 ohms
• Features our own Ezi-bias: User bias setting with switched tube selector and built in digital voltmeter
• 100 or 50 W selectable
• Fan cooling for longer life of critical components
• Low ESR capacitors: polypropylene and silver mica, not a ceramic or polyester cap to be seen.
• Resistors: mainly carbon film, metal film in critical stability areas such as plate resistors, metal oxide in high wattage applications. No carbon composition resistors used to keep noise low and stability high.

All the original Dumble Overdrive EQ options. Footswitch supplied.

We currently are using a switch mode power supply to supply 12V for relays and fan but will use a small transformer and regulator IC in production models due to reliability issues with the switch mode in guitar amp service.

See the pics. Enquiries welcome