813 PP Part 2

After years of trying many designs and failing to get them going properly, in 2018 I decided to have another go at this amplifier and this time do it in public on a forum.

The journey is documented here.

813 HT PSU

813 LT PSU

813 Audio

If I was to make some changes for this design it would be:

  • .Use 2 SMPS per valve of half the rating. It equals about the same cost but would perform better. Also use a CMC choke to feed the 813 filaments. This configuration echos Pete Millet’s solution as in his 813 amplifier. It would also enable the 1R current sampling resistors to be in the cathode instead of the anode therefore safer.
  • Give the driver its own HT supply
  • Upgrade the bias supply with more filtering

After getting to this stage, I am even more impressed by Ian’s amplifiers here.

This proved to be the end of the road for this amplifier which morphed into the GM70 here.