Interesting Experimental Circuits

#1 - WE417A/5842 Line Stage

This circuit has been tried, and is the result of several inquiries as to how this tube might possibly be used in such an application. The operating points are based on GE tube manual recommendations.. Tube specs and pinout are valid, design values are based on two possible supply voltage scenario's. This circuit is intended only for those who can debug and perfect it. If you are succcessful send me the details and I will add them here, I have not built or evaluated the performance of this particular circuit. See below...

Allan Rosenthall successfully completed the highest operating voltage version of this design and is quite pleased with the results..


  1. Only one channel is shown.
  2. 52mA total plate current at either 150V or 300V depending on topology choices.
  3. Low ripple on DC plate supply is a must, DC filament power is also a good idea.
  4. Line Amplifier is phase inverting.
  5. Voltage gain is estimated at ~27dB.
  6. Small output transformer with 3Kpri, 8 - 16 secondary and you have a headphone/power amplifier (est. 1Wout, Vs=150V only)

In the years since I wrote this I have used the 5842 extensively and can recommend it as a very good sounding tube indeed. It is the basis of my headphone amplifier which might eventually be featured on these pages and is a versatile and capable tube. The 417A has become very expensive but the Raytheon made equivalent 5842 is very good and more readily available at a somewhat lower price.

Many spud amps have been based on the 5842, both parafeed and conventional SE, about 1Wrms is the maximum output, nestling comfortably between the 71A and the 45 in terms of output power with much less circuit complexity required. Note that my recommendation to use it this way in 1998 might have been ahead of the curve. (grin)

KRK 11/27/2005

417A Line Amp Proposal

As promised here is the schematic in unrestricted/printable PDF format 11/27/2005

© 1998, 2001, 2005 By Kevin Kennedy