Hum filter ETI 1979 - UK Vintage Radio Repair and Restoration Discussion Forum

captainking · 1st Jan 2016, 3:09 pm

Don't know if anyone has use for this but just been reading my old mags for some vintage'ish ideas
Regards steve

Radio Wrangler · 1st Jan 2016, 5:39 pm

Ah but are they notching 50Hz or 100Hz?

David

captainking · 1st Jan 2016, 5:59 pm

50

Steve

Radio Wrangler · 1st Jan 2016, 6:52 pm

It's the twin-T notch circuit. At 50Hz its set to remove induced hum and common-mode current coupled hum, but not the 100Hz ripple from full-wave rectifiers.

With the grotty mains waveform today, induced hum will include a lot of 3rd and 5th harmonics

David

Restoration73 · 2nd Jan 2016, 7:32 am

It works well. I built and used one to remove 60Hz hum from a U.S. live recording.

Skywave · 2nd Jan 2016, 8:24 pm

Quote:

Originally Posted by Radio Wrangler

It's the twin-T notch circuit. At 50Hz its set to remove induced hum and common-mode current coupled hum, but not the 100Hz ripple from full-wave rectifiers.

Build two T-sections, one at 50 Hz, one at 100 Hz, connected in series, perhaps with a buffer between?

Al.

captainking · 2nd Jan 2016, 11:05 pm

I have found another circuit that covers both in one circuit

Steve

1st Jan 2016, 3:09 pm	#1
captainking Retired Dormant Member Join Date: Dec 2015 Location: Barnsley, South Yorkshire, UK. Posts: 172	Hum filter ETI 1979 Don't know if anyone has use for this but just been reading my old mags for some vintage'ish ideas Regards steve Attached Thumbnails

1st Jan 2016, 5:39 pm	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,902	Re: Hum filter ETI 1979 Ah but are they notching 50Hz or 100Hz? David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

1st Jan 2016, 5:59 pm	#3
captainking Retired Dormant Member Join Date: Dec 2015 Location: Barnsley, South Yorkshire, UK. Posts: 172	Re: Hum filter ETI 1979 50 Steve

1st Jan 2016, 6:52 pm	#4
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,902	Re: Hum filter ETI 1979 It's the twin-T notch circuit. At 50Hz its set to remove induced hum and common-mode current coupled hum, but not the 100Hz ripple from full-wave rectifiers. With the grotty mains waveform today, induced hum will include a lot of 3rd and 5th harmonics David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

2nd Jan 2016, 7:32 am	#5
Restoration73 Nonode Join Date: Jun 2013 Location: Surbiton, SW London, UK. Posts: 2,801	Re: Hum filter ETI 1979 It works well. I built and used one to remove 60Hz hum from a U.S. live recording.

2nd Jan 2016, 11:05 pm	#7
captainking Retired Dormant Member Join Date: Dec 2015 Location: Barnsley, South Yorkshire, UK. Posts: 172	Re: Hum filter ETI 1979 I have found another circuit that covers both in one circuit Steve