15-12-2016, 09:04 AM
(This post was last modified: 15-12-2016, 09:07 AM by Valvebloke.)
Yes, I know Andy's in France. If kit is used in a country where one side of the mains is 'neutral' (i.e. close to ground potential) then the polarity effect can still be an issue though. I understand that the French wiring code now encourages installers to wire sockets with a live-to-the-right convention although I guess it will take a long time for this to become a near-universal norm.
In my particular amp the mains switch isn't paired with a control in the audio chain (volume or tone or channel selection). It's the HMV 555 Stereoscope and the switch is on the back of the gain control for the oscilloscope deflection amps. The 50Hz still leaks into the audio path though and, irritatingly, the leakage is disproportionately into the left channel. So I can't null it out simultaneously in both channels using the 'humbucker' pot which shifts the heater voltage centre point :-(. Ho hum (ha, ha).
EDIT: The solution might be to put a braid screen over the wires to and from the mains switch and then ground this to the chassis, and maybe put a bit of copper screening around the switch body too. But there was none of that in the original amp.
VB
In my particular amp the mains switch isn't paired with a control in the audio chain (volume or tone or channel selection). It's the HMV 555 Stereoscope and the switch is on the back of the gain control for the oscilloscope deflection amps. The 50Hz still leaks into the audio path though and, irritatingly, the leakage is disproportionately into the left channel. So I can't null it out simultaneously in both channels using the 'humbucker' pot which shifts the heater voltage centre point :-(. Ho hum (ha, ha).
EDIT: The solution might be to put a braid screen over the wires to and from the mains switch and then ground this to the chassis, and maybe put a bit of copper screening around the switch body too. But there was none of that in the original amp.
VB
Ampregen Ltd http://www.ampregen.com
