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retailer · 24th Nov 2019, 11:55 pm

In the lead up to my recent Fender amp build I checked out a lot of other scratch amp builds just to see how others had done it and more than once other constructors mentioned correct phasing of the heater/filament wiring i.e. bridged pins 4 and 5 of the pre-amp valves are all on the same daisy chained twisted filament wire similarly pin 9 of the pre-amp valves are all on the other daisy chained twisted filament wire - I hope my explanation is clear, the idea being that this aids in reducing hum. I can't see that it would make any difference as the filament voltage is AC and indeed I did not bother to do this and both of my recent amp builds were very acceptably quiet - standing around 1m away from the amp with volume on 10 I could hear a faint hiss put my ear next to the speaker grill I could hear a faint hum.

Is this 'correct phasing of the filament wiring' just another keyboard expert idea or is there something to it ?

24th Nov 2019, 11:55 pm	#1
retailer Heptode Join Date: May 2005 Location: Adelaide, South Australia Posts: 541	Filament wiring 'Phasing' In the lead up to my recent Fender amp build I checked out a lot of other scratch amp builds just to see how others had done it and more than once other constructors mentioned correct phasing of the heater/filament wiring i.e. bridged pins 4 and 5 of the pre-amp valves are all on the same daisy chained twisted filament wire similarly pin 9 of the pre-amp valves are all on the other daisy chained twisted filament wire - I hope my explanation is clear, the idea being that this aids in reducing hum. I can't see that it would make any difference as the filament voltage is AC and indeed I did not bother to do this and both of my recent amp builds were very acceptably quiet - standing around 1m away from the amp with volume on 10 I could hear a faint hiss put my ear next to the speaker grill I could hear a faint hum. Is this 'correct phasing of the filament wiring' just another keyboard expert idea or is there something to it ?