18th Niccolò Anniversary (12AX7+EL84)

Some time ago my son turned 18. He came to me and asked for a stereo set as a birthday present. I said, that I would buy one for him. He replied that I did not understand. What he wanted was a vacuum tube amplifier “built by me”. The only additional requirement was that he should have been able to connect his mobile phone to it, using Bluetooth. This is how the ” 18th Niccolò Anniversary ” originated. I basically used the design of “Il Terzo“, with some modifications, due to the use of a different power transformer, and the addition of a Bluetooth module.


>>Measures coming soon<<

  • Push-Pull stereo integrated amplifier
  • Max Output Power 2x ~12W
    • @ 1 Volt peak input signal, with 16dB global negative feedback
  • Power Stage: 2x 2 EL84 power vacuum tubes in Push-Pull Ultra-Linear configuration and fixed bias
  • Phase Split Stage: DC coupled Concertina with 12AX7 vacuum tubes
  • Input Stage: 12AX7 vacuum tubes with self bias and bypass capacitor
  • Class AB with 28 mA anode current bias
  • Output Transformer: Hammond 1650E
    • Primary: 8K Ohm C.T., 40% screen tap
    • Secondary: 4, 8, 16 Ohm
  • Power Supply Unit Transformer: Hammond 370HX 550V c.t@230mA
  • Global Negative Feedback: 16dB
  • THD (measured with Sovtek 12AX7 LPS + JJ EL84)
    • at 1W: TBC
    • at 5W: TBC
    • at 10W: TBC
  • Two only capacitors in the signal path
  • 4, 8 Ohm Speakers
  • Input Impedance: 100K Ohm
  • Output Impedance: TBC
  • Damping Factor: TBC
  • 3 selectable input sources
  • Bluetooth input

Vacuum tube amplifier schema (LTSpice simulation screenshot)

Schema Il Terzo

Power supply schema for the vacuum tube amplifier (LTSpice simulation screenshot)



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