Beast_of_burden
Active Member
Hello Gents,
Just completed putting together a JE Labs design 2A3 SET with help from HFV member Radium. Amp is making music but there is a really loud 50Hz hum that is simply unacceptable. This design has been implemented countless times with inaudible hum.
I need help from an expert in Bangalore who can troubleshoot and fix the ground loop hum. I have to confess this is way beyond my pay grade. The amp was initially implemented with Star ground but this is not recommended by the designer so have now implemented sectional grounding atleast for the inputs. When I say inputs it's the RCA, Volume potentiometer and cathode resistor ground leads. Hum remains. It's loud and independent of position of potentiometers. It's loud enough that I can hear it in the next room 20 feet away.
The PS capacitor leads have all been grounded to the chassis at a single point. I lifted this and the hum disappeared but it also stopped playing music. I don't know what this means.
Hari has suggested replacing the paralleled 100uf electrolytic caps for the cathode resistor with MPP or MKP capacitors. I am trying to source those locally but it's hard during these times.
I live in South Bangalore, please help. I've attached the schematic. I can also provide pictures of the amplifier internals, but really what I am looking for is an expert who can "read" the schematic, take some measurements and suggest changes to the grounding scheme.
Signed
Frustrated with that old demon - Hum
Just completed putting together a JE Labs design 2A3 SET with help from HFV member Radium. Amp is making music but there is a really loud 50Hz hum that is simply unacceptable. This design has been implemented countless times with inaudible hum.
I need help from an expert in Bangalore who can troubleshoot and fix the ground loop hum. I have to confess this is way beyond my pay grade. The amp was initially implemented with Star ground but this is not recommended by the designer so have now implemented sectional grounding atleast for the inputs. When I say inputs it's the RCA, Volume potentiometer and cathode resistor ground leads. Hum remains. It's loud and independent of position of potentiometers. It's loud enough that I can hear it in the next room 20 feet away.
The PS capacitor leads have all been grounded to the chassis at a single point. I lifted this and the hum disappeared but it also stopped playing music. I don't know what this means.
Hari has suggested replacing the paralleled 100uf electrolytic caps for the cathode resistor with MPP or MKP capacitors. I am trying to source those locally but it's hard during these times.
I live in South Bangalore, please help. I've attached the schematic. I can also provide pictures of the amplifier internals, but really what I am looking for is an expert who can "read" the schematic, take some measurements and suggest changes to the grounding scheme.
Signed
Frustrated with that old demon - Hum