How much hum is too much?

[Chad Hauris]

You should not be able to hear any hum except maybe a small amount if the ear is held right to the speaker...if you can hear it humming at a usual distance then it's too much...there may be heater to cathode leakage in the audio output tube introducing hum from the AC filament circuit in the audio circuit. Would recommend trying a known good output tube.

[vintagecollect]

If all tubes are good, try larger cap values for power supply. Later ac/dc sets have slight disadvantage of no choke in power supply or field magnet /choke found in older speakers to further smooth out ac ripple in power supply. This should have some effect, especially if hum is annoying while trying to listen to set at lower volumes. Some reference books say some hum is acceptable, but by todays standards, probaly not for most people.
As a further note: A half wave rectifier will have more AC ripple voltage than Full wave rectifier output voltage using same filter caps. Give it a shot and let us know!!!!