Frequency Central – Thermo Nuclear – Full DIY Kit

£80.00 (Excl. VAT)

A high gain sub-miniature vacuum tube based overdrive

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SKU: Kit_FC_Thermo_Nuclear Categories: , , , Brand: HP Size: 4 HP


ThermoNuclear is a sub-miniature vacuum tube based overdrive. The first stage is a MOSFET with switchable mu-amp. The second stage is a self-biased sub-miniature pentode with switchable triode/pentode. Then there’s a tonestack based on the EH Big Muff. Finally, there’s a blend control and another MOSFET stage for some gain recovery after the tonestack. ThermoNuclear will crush and destroy your tone with a pleasing warm tubey goodness!

Although the filament of the tube will glow, it’s not a lightbulb, and the level of glow may vary between different tubes.

Thermo Nuclear – Build Document

About the LEDs

There are 3 LEDs in this design:

  • The two on the main PCB are being used for their diodic properties to protect the MOSFETs. Whether they light up or not is irrelevant (they might, just a tiny bit).
  • The third LED on the sockets PCB is used to bias the tube’s cathode. This has the same effect as a bias resistor with a perfect bypass capacitor. The LED will slowly come on as the valve warms up.


Q: Is this a Valvecaster/Safety Valve variant? 

A: Ha! In as much as you are a fish variant. No!

Q: Is the tube fragile?

A: Physically, yes – don’t drop it. Electronically the tube is as strong as a great mountain range which has stood for millions of years against wind, weather, war, plague, pestilence, famine and fascism.


  • Width: 4HP
  • Depth: 39mm
  • 12V draw: 175mA
  • -12V draw: 4mA


Additional information

Weight 0.114 kg
HP Size

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