4 Tubes manufactured by Hewlett Packard

• 

  12AX7A

  Amperex

  Branded Hewlett PackardAmperex

• 

  5751

  RCA

  Branded Hewlett Packard

• 

  

  

  

  12AU7, ECC82

  Amperex

  Branded Hewlett Packard

• 

  

  

  

  

  

  GZ34, 5AR4, F32

  Mullard

  Branded AmperexHewlett Packard