09-10-2019, 08:18 PM
It could be the reason why many radios had the transformer mounted actually ON the loudspeaker - to maximise the distance from the mains transformer.
Years ago I made an amplifier on a small chassis, first power-up (with O/P transformer not yet mounted) I didn't think it was working, there wasn't a squeak from the speaker. Until I applied an input! It blew me away, I just wasn't used to not hearing a faint hum or hiss. I named the chassis 'Humphrey" because it was hum-free...
Later, I mounted the output transformer, drilled holes in my lovely painted chassis, screwed it in place, switched it on, to my dismay I got a hum. Pulling the valves (EL41 and ECC82) the hum was still there. Worked out it was magnetic coupling between the mains and output transformers. Spoiled the project
It's called 'learning the hard way.'
Years ago I made an amplifier on a small chassis, first power-up (with O/P transformer not yet mounted) I didn't think it was working, there wasn't a squeak from the speaker. Until I applied an input! It blew me away, I just wasn't used to not hearing a faint hum or hiss. I named the chassis 'Humphrey" because it was hum-free...
Later, I mounted the output transformer, drilled holes in my lovely painted chassis, screwed it in place, switched it on, to my dismay I got a hum. Pulling the valves (EL41 and ECC82) the hum was still there. Worked out it was magnetic coupling between the mains and output transformers. Spoiled the project
It's called 'learning the hard way.'
