8mm Forum: Elmo Speaker Hum

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Posted by Roger Faires (Member # 4147) on March 27, 2015, 07:42 PM:

Hey Good Folks,

How hummy should one expect an Elmo ST 1200 HD's speaker to be? Seems mine might be a little be noisier than I think it should be. And that's while it's just in stasis with the power supply plugged in.

Thanks in advance
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Roger

Posted by Andrew Woodcock (Member # 3260) on March 27, 2015, 07:56 PM:

Not very Roger, these have superb amplifiers with minimum hum,good grounding and an extremely high gain amplifier.

Ordinarily the sound section on these machines should be the high point apart from the wow & flutter issues due to the tiny sound capstan drum and poor dancer arrangement.

When fed an external input into these amplifiers, the amplifier performs excellently. Are you still getting hum when trying this method just to test the amp and speaker?

Posted by Steve Klare (Member # 12) on March 28, 2015, 03:30 AM:

I'd say to an ear that's used to more modern audio, a lot of magnetic sound projectors seem hummy. When you turn on a new TV or stereo system, you really can't hear hum at any volume level that won't make the neighbors call the cops.

I normally run my projectors through an external amp with a lot of hum suppression, and when I go on the internal speaker on all of them I am very conscious of the hum (especially at first), even though it truthfully isn't that bad. If when you run the machine with even a low sound level it drowns out the hum, you're doing OK. When the hum starts to punch through, now you've got trouble!

I wonder if 16mm machines have the edge here since with their optical sound they are a lot more immune to pickup from stray magnetic fields.

Posted by Roger Faires (Member # 4147) on March 28, 2015, 06:41 AM:

Ok, so, without using an external speaker (or amp) but turning the volume down low - the hum is definitely not as apparent.

When Using an Elmo ES-650 single external speaker, which I just received yesterday, btw, the hum is the same; low when volume is low and quite a bit more discernible as volume increases - just transferred to the external speaker.

Maybe I should try , as a test, this little RCA amp I got? The kind radio shack would sell for $50. Now if I can figure out how to hook that up to the ST1200?!

Maybe I'm being just wet around the ears and not remembering the old days when everything machine was a tad noisier?

Posted by Steve Klare (Member # 12) on March 28, 2015, 07:04 AM:

If you can still find one, Radio Shack has (...had?) all sorts of cables you can use for adapting a projector output to an amplifier input. It's good to rummage through their website and find what you need and take part numbers to the store (or order online and pick up there).

It works better if you keep the cables short and everything plugged into the same outlet, especially if the amp is grounded.

What you might find too is if you run a good set of speakers, the bass response is better than the four inch speaker in an ST-1200 and it will seem a little hummier than running unplugged.

An old friend of mine always told me just a touch of hum is kind of comforting. Lately I understand what he means. When I turn on my amp and then turn on the sound on the projector, absolute silence is a sign something, somewhere isn't right!

Posted by Roger Faires (Member # 4147) on March 28, 2015, 07:16 AM:

Good Morning Steve,

So do I use the projector output for an EXTERNAL SPEAKER if I want to hook up an external amp or would it be going into the AUX output?

And yes, there is a slight lump in my throat whenever I hear noises of the past. Speaker hum inc. It's the same as hearing an old rotary dial phone ring. Not that I've heard that lately.

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Roger

Posted by Steve Klare (Member # 12) on March 28, 2015, 07:26 AM:

'Morning, Roger,

You want "Aux": it is the correct level for inputting to an amp. You can connect with a 1/8" (3.5mm) plug. It is a monaural output, so you need to split it if you are plugging into a stereo amp.

External Speaker is a power output: too much voltage.

on the ST-1200, Aux is controllable with the volume control, with the knob turned "Off", you will get nothing out of it. Aux also cuts of the internal speaker,

I recently connected in a Eumig 800 series. That's different: the volume knob only controls the internal speaker and it stays live when Aux is connected. I can actually crack open the volume a little and have another speaker working.

Posted by Roger Faires (Member # 4147) on March 28, 2015, 07:31 AM:

So now I just have to figure out the connector(s) to plug my ES-650 into that amp if I want to use that speaker? They got those crazy (I've never seen 'em before) flat prong with single pin above jacks. I just wanted my whole projection-sound family (sans amp) to be Elmo based. Seems respectful of all that Elmo has given us.

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Roger

Posted by Steve Klare (Member # 12) on March 28, 2015, 07:38 AM:

I'd say use the Elmo external speaker only with the Elmo output. If you run it with an external amp you may blow the speaker: it was only meant to deliver as much power as the projector's amp can provide.

-you go to an external amp for larger speakers...maybe many larger speakers!

That two terminal connector is the DIN loudspeaker plug, just like hum in your speakers they are not as easy to find these days. Steve Osborne sells them, and I think you find them on E-bay too.

Posted by Roger Faires (Member # 4147) on March 28, 2015, 07:51 AM:

Ah, Ok, good advice on the speaker. I'd hate to see any harm come to this ES-650 - not only because it is so cool looking with this nice 70's speaker cover fabrique and old school naugahyde wrapped cab but it came in the original box. And all for $39.00 ebay.

I've got a good little set of book shelf speakers I can use with an amp.

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Roger

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