8mm Forum: Hum in Audio Track

This is topic Hum in Audio Track in forum General Yak at 8mm Forum.

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Posted by Michael De Angelis (Member # 91) on April 09, 2005, 04:04 PM:

I have a Eumig 810D and 822D that when the sound worked properly
I could turn the bass - treble wheel under the volume control to adjust the sound.
But I noticed that on two occasions when I had this repaired, the circuit would not last and the audio would sound flat and muffled.

Another issue is that the sound track from these units produce Hum.
I know that they suggest moving the coils around the heads, but this
did not work for me.

Hence the Eumig's become Hum-migs.
Is there a notch filter or some solution that I could address, if not one but both of these issues with the projectors controls and the output of sound?

Michael

Posted by Paul Adsett (Member # 25) on April 10, 2005, 11:51 AM:

Hi Michael,
Yes adjusting the position of the hum bucking coil on the Eumig 800's only has a limited effect, but it is still worth moving it around to find the position of minimum hum. Then feed the amp output of the Eumig into a 10 band graphic equalizer (available from Radio Shack or Best Buy), and then from the equalizer into your stereo system. You can notch the graphic equalizer to eliminate most of the 60hz hum and also eliminate high frequency "clicking". You will get greatly improved sound quality.

Posted by Jan Bister (Member # 332) on April 10, 2005, 12:49 PM:

Wait - what do you mean by "high frequency clicking" Paul? I'm asking because my Chinon SP-330MV has precisely that problem with sound playback (only seems to occur during loud passages or those with strong high-frequency content, like cymbals in music or 's' sounds in speech)...

Posted by Paul Adsett (Member # 25) on April 10, 2005, 01:54 PM:

Hi Jan,
Well I'm not sure what I mean by high frequency "clicking" either! [Big Grin]

But it is something that I have definately heard on my Eumig 800's and it can be largely filtered out by notching all frequencies above about 10K. I have no idea what the cause is, but it seems to be most prevalent in speech rather than music, so it must be some sort of amplifier "peaking" problem. Some movies seem to exhibit this much more than others. Maybe some of our electronic experts on the forum can give us more insight to this problem.

Posted by Michael De Angelis (Member # 91) on April 10, 2005, 04:09 PM:

Paul said:

quote:
Then feed the amp output of the Eumig into a 10 band graphic equalizer (available from Radio Shack or Best Buy), and then from the equalizer into your stereo system.

Paul, where would I find the amp output of the Eumig to go into an equalizer?

Thanks again,
Michael

Posted by Kevin Faulkner (Member # 6) on April 10, 2005, 04:12 PM:

Jan, What you are describing is good old Super8 flutter. If the loop under the gate prior to the sound head has not got rid of all the film movement then this is the effect it has on the sound. This is one of the reasons that Elmo re-worked the film path on the later GS1200's. Its all down to design and there really isnt a lot that can be done about it.
This is never a problem with std 8 sound because the sound head is 54 frames after the picture so has plenty of time steady out again.

Kev.

Posted by Jan Bister (Member # 332) on April 10, 2005, 05:03 PM:

I see what you're saying Kevin, but that's not it - of that I'm quite sure. If the intermittent advancement of the film were "leaking" down to the soundheads then the clicking would be of a particularly rhythmic nature, moreover it would occur 18/24 times a second. The problem that my Chinon is having is definitely of electronic origin. But it's not THAT bad, so... what the heck! [Cool]

Posted by Paul Adsett (Member # 25) on April 10, 2005, 06:06 PM:

Michael: There is an amp line out socket on the Eumig 810's and 822's. It is on the front panel , the first socket from the front of the projector. The next one over (towards the rear) is the recording socket . This requires a special DIN plug , available from Radio Shack, and you wire up to terminals 2 and 3.

Kevin: I agree with Jan, I don't think this is film flutter. I know your not a Eumig man Kev, so you probably have never experienced this particular phenomenon- I have never heard it on my GS1200'S.

Posted by Michael De Angelis (Member # 91) on April 11, 2005, 03:36 PM:

Paul,

Thanks for the update, I will look for the plug and the 2, & 3 wiring configuration.
I also need to get an equalizer.

Best for now.
Mike

Posted by Paul Adsett (Member # 25) on April 11, 2005, 04:26 PM:

Michael, I suggest you take your projector with you to Radio Shack. They will recognize the required plug right away.

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