8mm Forum: Connecting EUMIG to Amplifier

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Posted by Henry Perangelo (Member # 40) on June 16, 2003, 09:56 AM:

Hello,

Does anyone have any experience with connecting an EUMIG (810 or 824) to an amplifier for playback. I notice that "line output" is a female five pin din connector. I have a EUMIG plug that is a three pin male which doesn't seem to work. If you have experience please provide connection details.

Thanks,
-Henry-

Posted by Tim Christian (Member # 48) on June 16, 2003, 01:37 PM:

According to the manual, line output uses a three-pin plug and a 100 kohm source is between pins 2 (earth) and pin 3.

Posted by Henry Perangelo (Member # 40) on June 18, 2003, 12:14 PM:

Does anyone have any experience with connecting an EUMIG (810 or 824) to an amplifier for playback. I notice that "line output" is a female five pin din connector. I have a EUMIG plug that is a three pin male which doesn't seem to work. If you have experience please provide connection details.

Posted by Tim Christian (Member # 48) on June 20, 2003, 03:55 AM:

It seems inherently improbable that a manufacturer who wanted to stay in business would go to the trouble of providing a dummy connection and false documentation for a non-existent function!

For the record, the line output on my 810 does work. The output level seems a little high for the phono input of a modern amplifier. The CD input may be more suitable.

Posted by Henry Perangelo (Member # 40) on June 29, 2003, 12:02 PM:

Thanks for the reply Tim.

When you connect to "line output" (on EUMIG) to your amplifier for playback, is sound to the internal speaker cut? When I do
this connection I still get sound out of the internal speaker.

Am I doing something wrong?

Thanks,

-Henry-

Posted by Mal Brake (Member # 14) on June 29, 2003, 12:42 PM:

If I may jump in here, no the internal speaker does not get cut off when connecting an Eumig to an external amplifier via the 5 pin din socket. Good luck.
Mal

Posted by Paul Adsett (Member # 25) on June 29, 2003, 01:11 PM:

Henry,
The projector's internal speaker is only disconnected when you plug in the 2-pin external SPEAKER connector. When you use the line output to go through an external amplifier, the projector speaker is still functional and you can operate it independently of the external amplifier system. It is a good idea to connect the line output into a 10 band graphic equalizer and then into the amplifier, so that you can filter out the 50 or 60 hz hum which is the plague of the Eumig 800 series projectors. The 900 series Eumigs have very low hum, but even with these machines (or any 8mm projectors for that matter) an equalizer really can make a huge difference in sound quality by reducing low frequency hum and rumble, and high frequency hiss. Expect to pay about $85.00 to $150.00 for a Yamaha or Radio Shack equalizer.

Posted by Kevin Faulkner (Member # 6) on June 29, 2003, 04:08 PM:

I agree with Paul about the hum level on the 800 series, it was really bad. Anyone using one of this series of machines can reduce the hum some what by removing the from cover and looking behind the vol control you will see a round coil suspended on a strip of metal. This is the hum buck coil for cancelling out magnetic fields and if moved about a position can be found to give minimum hum. I have to say minimum hum because it can NOT be eliminated. The same thing applies to the Elmo range of machines. Under the heads there are one or two yellow coils deending on the model (one or two tracks) and these can be moved about virtually eliminating all hum.
Kevin.

Posted by Tim Christian (Member # 48) on June 29, 2003, 06:45 PM:

Since most amplifiers these days are stereo, it is worth splitting the Eumig's mono output. From the Eumig output, connect two resistors of about 47 kohm, one to each amplifier input. This way you can use both channels. By setting the amplifier's tone controls or equalizer a little differently, you can give a slight stereo effect to the sound.

The Eumig hum is essentially 100 Hz hum. Remove this with a filter on the auxilliary amplifier's inputs.

Posted by Dan Lail (Member # 18) on June 30, 2003, 12:09 AM:

Hi, Tim, I have a couple of Elmos and both have a low end hum when I run them through my Alesis Mixing Board which is connected to 50watt per channel Pioneer receiver/amp. What is the nature of this hum? I have a twenty ban analog eqaulizer in line, but I hate to pull out the hum with it because I also take off some of audio spectrum. Most people would not notice the hum. I'm an audio freak and any unnatural electronic noises really bother me. I've tried different gain ratios, but no luck. Of course, the equalizer does eliminate it and at the same time eliminating the booming bottom end.

Dan

Posted by Kevin Faulkner (Member # 6) on June 30, 2003, 06:26 AM:

Hi Tim,
100Hz Hum??? USA. Surely it would be 50 or 60Hz as its due to the mag field from the transormer or is it doubled due to the colapsing effect of the mag field. Mag fields and the hum they cause was never one of my forte's.

Kevin.

Posted by Henry Perangelo (Member # 40) on June 30, 2003, 08:47 AM:

Great responses. Thank you all!
I think the info will help.
-Henry-

Posted by Steve Klare (Member # 12) on June 30, 2003, 01:16 PM:

Has anybody ever tried replacing the electrolytic capacitors in the power supply circuits on these projectors? They are very age sensitive, as time passes the electrolyte dries out and their capacitance drops way down. This would contribute to the 100cycle/120cycle hum.

I work for a power supply company and we will not ship product from stock with capacitors over 5 years old, and these are high grade commercial parts, not the cheapy stuff in consumer goods. The failure mode here would be high ripple (hum if the load is audio.)

The benefit would be that a modern electrolytic is smaller than the 1970s equivalent, so you could put a larger cap in and get even better performance than original.

The reason that the folks in the 50 cycle countries are seeing 100 Cycle hum is that the power supply has a full-wave bridge rectifier at the front end, and when you full-wave rectify a sinusoid the frequency doubles. In the land of 60 cycle, we'd get 120 cycle hum for the same reason. This is another reason I suspect the power supply filtering.

Posted by Paul Adsett (Member # 25) on June 30, 2003, 04:05 PM:

Steve,
Where is a good source for electrolytic capacitors? Do Radio Shack still sell them?
I could be wrong, but I think I read somewhere that a major source of hum on some S8 sound projectors is due to inadequate shielding of the magnetic sound heads from the strong 50 or 60 hz magnetic fields generated by the massive mains transformers used in these machines.

Posted by Kevin Faulkner (Member # 6) on June 30, 2003, 04:32 PM:

Paul, Thats exactly what I knew to be the case especially as these machines had bad hum from new. And also the fact that most 8mm machines have hum buck coils to cancel out hum induced by magnetic fields tell me that this has always been a problem.
I would still try adjusting the hum buck coil.
I have done this on my GS1200 and the hum level with the vol control full up is virtually non existent as it should be if they are adjusting correctly.

Kevin.

Posted by Steve Klare (Member # 12) on June 30, 2003, 05:00 PM:

I'm sure that Radio Shack could help out with electrolytic capacitors(Hadn't thought about it, I was just going to grab a few at work!)

Even if there is a noise cancellation circuit in place, the quality of the supply voltage is going to be a big contributing factor, and at the age of these machines those caps have to be pretty tired.

Just try to find a capacitor which is at least as many Microfarads and at least as many Vdc, and you'll be fine.

Please remember that these are polarity sensitive, and will make a mess of the insides of the projector if they are in backwards.

Tell you what! Next weekend I'll yank the caps out of my projector and bring them to work and measure them. If they are bad I'll replace them and post the results here. (I've been putting this off, now I've got an incentive!)

Posted by Steve Klare (Member # 12) on July 08, 2003, 09:43 AM:

Well,
I yanked the electrolytics and brought them to work. They check out fine (much to my surprise, this is usually the reason for hum on old audio equipment).

I'm thinking of putting in new ones of higher quality and value, to at least reduce the ripple on the rails of the sound board.

I'm also wondering if I can sneak some shielding around the sound head and reduce the pickup. (Did they really have to put the main transformer right next to it??!!)

Posted by Tim Christian (Member # 48) on July 08, 2003, 01:00 PM:

Sorry, guys, I have been trying to find a couple of hours to check out the hum on my Eumig. I haven't bothered up til now because it really isn't that bad. However, now I'm building a couple of pipe-loaded speakers for enhanced bass, I must take a look.

Job one is to check the cause: if the 'scope shows 50/60 Hz hum, then it is pick up; if it proves to be 100/120Hz then it is power supply. There doesn't seem to be a hum cancellation facility in the 810D circuit.

I'll post the results as and when.

Posted by Steve Klare (Member # 12) on July 08, 2003, 01:47 PM:

Sounds Good Tim,

I don't have a scope at home, and can't bring a movie projector to work and appear to be doing my job!

(They don't like me bringing oscilloscopes home either!)

Posted by Kevin Faulkner (Member # 6) on July 08, 2003, 05:15 PM:

Tim/Steve,
I'm 99.9% sure you will find its 50/60Hz hum form the mains transformer. On the 802 there is a coil suspended behind the volume control. Its in series with the rec/playback head. With the side plate removed it's possible to see it. Moving it arround will have a cancelling effect on the hum heard through the speaker.
I will be interested however Tim on the findings with your scope.

Kevin.

Posted by Henry Perangelo (Member # 40) on July 21, 2003, 02:10 PM:

I finally got my EUMIG hooked-up to my Amplifier! It turns out that my EUMIG "line-out" plug was bad. I made a new one (with parts from Radio Shack). The sound is wonderful. So, now my sound setup is as follows: from the EUMIG to "Radio Shack 3-Channel Stereo Sound Mixer/Equalizer) and then to my Amplifier. My EUMIG never “sounded” better.

I’m also feeding my 16mm projector to the Mixer/Equalizer, but that is a discussion for another forum...

Everyone thanks for your responses,
-Henry-

Posted by Mal Brake (Member # 14) on July 21, 2003, 02:21 PM:

I'm pleased you had a good result at last, Henry. Trying to get good line-out sound was always, er, 'fun' to say the least

Posted by Henry Perangelo (Member # 40) on July 21, 2003, 02:24 PM:

Thanks Mal!

Posted by Steve Klare (Member # 12) on August 24, 2003, 11:39 PM:

Regarding the Hum Issue, I noticed it was really bad on my projector when I use the external speaker, not the internal one which is smaller. I figure the designers didn't count on the low frequency response of the external speaker when they designed the ripple filter for the sound board power supply. So I went looking for a modern electrolytic filter capacitor to replace the existing one. I lucked out, I managed to go from 2,200 uF to 5,600 uF in the same sized package.

I would say the hum has dropped out of the obnoxious range, it's not even audible in the bottom half of the volume range. It's definitely still there though, so I'll concede at least a partial victory to the pick-up folks.

did anybody aever make those oscilloscope measurements?

Posted by Tim Christian (Member # 48) on August 25, 2003, 02:16 AM:

Sorry, guys. I've been trying to find time to spend half-a-day at it. Just at the moment, I'm squeezed between work (customers are unusually active for the time of year) and trying to get a boat back in the water before the weather breaks!

Next wet day, I'll get down to it - promise! [Roll Eyes]

Posted by Michael De Angelis (Member # 91) on September 01, 2003, 02:28 AM:

Dear Friends,

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

Posted by Steve Klare (Member # 12) on 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!

Posted by Henry Perangelo (Member # 40) on 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!

Posted by Tim Christian (Member # 48) on September 23, 2003, 11:34 AM:

This is my solution to the connection problem:
connector box

Amplifiers with graphic equalizers can be set up to the required equalization or noise filter properties.

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