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Author Topic: One for the Audiophiles
Andrew Woodcock
Film God

Posts: 7477
From: Manchester Uk
Registered: Aug 2012


 - posted May 16, 2017 07:40 AM      Profile for Andrew Woodcock         Edit/Delete Post 
Your Eumig 810D Gary, will no doubt have the "Hum Bucking" coils fitted to it that is spoken about in T10 or T60 thread here recently.
As was pointed out there, it is possible to further reduce hum initially by carefully finding the optimum position of those coils within your internal layout of your machine.
Further noise cancelling may be brought about by earth loop isolation leads,plugs and sockets in between your eventual output or initial input to your mixer, similar to the type shown here...

https://www.kenable.co.uk/product_info.php?products_id=8073&gclid=CMHL0dO09NMCFYe_ 7QodHvEBiw

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"C'mon Baggy..Get with the beat"

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003


 - posted May 16, 2017 09:11 AM      Profile for Steve Klare   Email Steve Klare   Send New Private Message       Edit/Delete Post 
The balanced input does a tremendous amount all by itself.

I have active ground loop cancellation down at the amplifier end (I have 30 feet of cable between the projectors and my amp: there can be quite a difference in ground voltage between outlets that far apart.), so that's taken care of already.

-but if I have something well grounded (like an Elmo) and something not so much (like a Eumig) both grounded together, I can have a local ground loop right on the table. This would apply to a well grounded amp too if all the cables were short.

It's a shame this stuff doesn't always act the way it did on the chalkboard in Electronics Class! (-when there were chalkboards!)

Ground isn't always as "groundy" as we'd like it to be!

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All I ask is a wide screen and a projector to light her by...

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003


 - posted May 17, 2017 09:04 AM      Profile for Steve Klare   Email Steve Klare   Send New Private Message       Edit/Delete Post 
quote:
Steve, I've re-read your 'Adding a Mixer' thread and despite not being sure I follow your explanation of the issue, I'd sure like to take you up on your kind offer to describe your soldering work-around.
Sorry I missed this!

Here's how you cook up a balanced monaural connection between a Eumig 800 series and your mixer.

You will need:
One Din Male connector
One 1/4" stereo phono plug

One or other of these should be on one end of a shielded cable. (The other end should be dangly wires.)

You connect like this:

Din Pin 3 to the Phono tip
Din Pin 2 to the Phono ring

The shield of the cable gets connected either to the phono sleeve -OR- the projector chassis, but not (NEVER, EVER!) both. If you connect ground at both ends you're right back to having a ground loop again.

 -

How this works is it presents two connections to the mixer. The mixer input just subtracts the two voltages and whatever ground disturbance is on both gets taken out in the math.

You should also bear in mind: You are listening to 40 year old equipment with modern ears and you may be setting the bar too high as far as hum goes, especially with these machines. They are actually very good, but low hum is not their strong point.

I have been messing with this stuff for years. (One of these was my first sound machine 15 years ago.) I have muffled the hum, but I haven't exactly killed it!

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All I ask is a wide screen and a projector to light her by...

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Gary Baker
Film Handler

Posts: 34
From: Glasgow, Scotland
Registered: Apr 2017


 - posted May 17, 2017 01:03 PM      Profile for Gary Baker   Email Gary Baker   Send New Private Message       Edit/Delete Post 
That's an awesome tutorial. Many thanks for this!

This will be my next project when work and parenting permits. I'll also try the coil adjustment Andrew mentioned and report the results when complete.

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003


 - posted May 17, 2017 03:03 PM      Profile for Steve Klare   Email Steve Klare   Send New Private Message       Edit/Delete Post 
Something that is kind of wild about all this is how much of a difference human perception plays in it.

I ran on the small speaker in my machines for years because anything I hooked up between a projector and my amp sounded absolutely awful! I finally dug down to the bottom of it and I built a setup that works. It sounds much better and this became the new normal.

I can't lug all this stuff with me everywhere, so when I travel someplace I go unplugged and return to the internal speaker.

First night or so, any machine I have sounds really terrible: there is audible hum, and some hiss, and the bass is kind of thin. It's no different than years ago, it just bothers me now.

-but a couple of days later it sounds OK, maybe even good.

Just the same: You crank the volume on a modern TV or audio system, you can be up to downright deadly volume levels and not pull up hum.

If you listen to these machines with these kinds of ears, your ears may not be happy at first.

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All I ask is a wide screen and a projector to light her by...

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Ken Finch
Jedi Master Film Handler

Posts: 543
From: Herne Bay, Kent. U.K.
Registered: Oct 2011


 - posted May 19, 2017 01:25 PM      Profile for Ken Finch   Email Ken Finch   Send New Private Message       Edit/Delete Post 
Hello Gary. I have been reading through all the responses to your post and thought I would add my "Tuppenceworth". I also have a 810 D and play the sound through a Yamaha AV amp. It is an older model than yours a DSP-A5 and was a "Best Buy" for its price range in the test reports of its day. The "line out" socket on the projector is indeed mono and the wires are soldered to p1ns 2 and 3 of the DIN plug (centre wire to pin 2) The projector manual has a diagram of this and also states that line output is.5-1.5volts. 50kOhms. I do connect via a mixer, a "realistic" stereo disco mixer, sold by "Tandy" many years ago. The cable from the projector is connected to one of the "phono" inputs of the mixer.
This has a switch to output the signal as mono or stereo. The output is then connected to the C.D. analogue input sockets of the Amp. The effect system is switched off and the sound then comes from the left and right main speakers, although using the "mono Movie " programme on my Yamaha often works well. Just like I remember the sound in the cinema of my youth! I do not get any problems with hum or unbalanced sound from the speakers. I also use the same system for the sound from my Bauer stereo projector or 16mm machines with a line out socket including my old 9.5mm Pathe PAX. The latter being via a photo transister via a mike input of the mixer! My amp does not have HDMI or component video input sockets but plenty of composite S video and some optical and coaxial sound sockets. I can therefore use it for VHS tapes and Laser discs as well as tape recorders and record players. I guess I am showing my age. Good luck with your set up. Ken Finch. [Smile]

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003


 - posted May 19, 2017 01:41 PM      Profile for Steve Klare   Email Steve Klare   Send New Private Message       Edit/Delete Post 
That ".5 to 1.5V" spec always gets me!

-if the soundtrack is quiet...where is this half a volt minimum signal coming from?! [Wink]

Is this supposed to be the hum? (Let's HOPE not!)

An optically isolated (phototransistor) input is the absolute best way to bust a ground loop. Unfortunately I discovered this about 6 weeks after I built what I have (and I'm too lazy to start all over again!). It works very well, it's just really picky about how it's connected.

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All I ask is a wide screen and a projector to light her by...

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Andrew Woodcock
Film God

Posts: 7477
From: Manchester Uk
Registered: Aug 2012


 - posted May 19, 2017 01:49 PM      Profile for Andrew Woodcock         Edit/Delete Post 
I am surprised to hear your mixer outputs are being connected to the CD input on your HC Yamaha Amp Ken.

Are your "Aux" input already in use for other equipment?

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"C'mon Baggy..Get with the beat"

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Gary Baker
Film Handler

Posts: 34
From: Glasgow, Scotland
Registered: Apr 2017


 - posted May 20, 2017 05:09 AM      Profile for Gary Baker   Email Gary Baker   Send New Private Message       Edit/Delete Post 
Well, I soldered the cable and it works a treat! By playing around with the gain control and other levels the hum's been minimised to the point where it's barely there. Thanks once again for the info, Steve...it's a real advantage being able to implement the fruits of research and the tinkerings of others.

Ken, yes, my Yamaha has a number of 'effects' options that allows you to change the 'Theatre' quality of the sound output. It's been fun messing around with this, espeically as some settings mimic the audio feel of 'Roxy Cinema,' 'Cellar Club,''Music Hall' and a number of others. The pro-Logic even provides a basic 5 speaker surround though I think limiting the mono to the two front speakers gives the best results.

I'm really pleased with this set up now as my HD projector is placed permanently on a shelf and the placing and readying of the cine projector on it's stand takes mere minutes. Last night, just as a test reel, I watched Disney's 'Black Hole' and was impressed by the step up in sound quality with the dialogue nice and crisp and John Barry's excellent score coming over very nicely.

I'm sure I'm not the only person here to have dreamed of owning a cinema as a kid but this really is a joy to me.

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Ken Finch
Jedi Master Film Handler

Posts: 543
From: Herne Bay, Kent. U.K.
Registered: Oct 2011


 - posted May 20, 2017 06:42 AM      Profile for Ken Finch   Email Ken Finch   Send New Private Message       Edit/Delete Post 
Hi Andrew. In answer to your question about other inputs on my Yamaha amp, the answer is "yes". I have DVD player, DVD Recorder, Vhs Tape Recorder, Laserdisc player and Sky box. connected and can therefor switch to whichever source I want to project or listen to. Best wishes Ken Finch. [Smile]

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Andrew Woodcock
Film God

Posts: 7477
From: Manchester Uk
Registered: Aug 2012


 - posted May 20, 2017 07:15 AM      Profile for Andrew Woodcock         Edit/Delete Post 
Ok thanks Ken.

--------------------
"C'mon Baggy..Get with the beat"

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