A Better Very Compact Tube Hybrid

This amp is a Rev of the original CTH amplifer. There are just a few small changes to make the amp more robust and fun. These changes are:

  • Q1P is changed to 2N4922 (TO126) for higher power dissipation.
  • C1H, C2H increased to 150u taking advantage of a new series of caps.
  • New resistors have been added to the heater circuit to give two more switchable voltages for a total of four separate voltages.
  • More room has been made around C4L/C4R to make it easier to install other type coupling caps.
  • More room to help fit the heatsink on the 24V regulator.

See the CTH amplifier section for most build and wiring instructions.


The Power Supply

The full CTH Rev A power supply includes the LV and HV supplies and the heater supply.

Some of the features of the new supply are:

  • TO126 2N4922 for Q1P.
  • Four heater voltage settings. (see BoM).
  • More room for the 24V regulator heatsink.
WARNING - 100VDC is significant high voltage. Every precaution for handling HV should be exercised.

CTH Rev A Power Supply

Full Excel BoM

This Excel spreadsheet has the parts lists and part numbers for the 2026 (Rev A) version of the Compact Tube Hybrid PCB. Most of the parts have Mouser part numbers. A few key components come from Digikey.

CTH Rev A 2026a Excel BoM