I have a film friend that formally collected 8mm. Today he strictly collects 16mm. During that time he solved the "hum" that emanates during playback.
He emulated the "hum sound" by playing a series of similar octave sounds on his trumpet, recording it for playback for another friend that specialized in electronics.
His friend isolated the tones into electronic filters using a notch switch, ultimately connecting the unit and selecting the filter that matched his machine and knocking out the hum during playback. Nevertheless, it worked.
I do not know if the switch was a type of potentiometer linked to circuitry.
Unfortunately, he disposed of the unit over 20 years ago.
Maybe there is musician and an electronics buff, that can configure this type of unit again.
I know that I would pay for a schematic of this type of unit.
Best,
Michael
-------------------- Isn't it great that we can all communicate about this great hobby that we love!
Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003
posted September 02, 2003 10:58 PM
I think the ultimate way around this could be a feed forward circuit. Basically what this does is what the hum correction circuit is trying to do. It would take a sample of the line voltage and run it through an op amp circuit set up to subtract the sample out of the audio output signal. This would be fed into the input of the power amplifier. Since the amount of line frequency signal subtracted out would be fixed, it would not effect low frequency signals that are supposed to be there.
Any good analog designers out there? I might have been able to do it at one time but for the past 4 years I've been scribbling proposals!
-------------------- All I ask is a wide screen and a projector to light her by...
posted September 03, 2003 11:04 AM
I vote for using an equalizer to filter out the "hiss". I know some of you purists may protest, but it very simple, safe, and does the job without much signal loss and without much fuss!