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Topic: One for the Audiophiles
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Steve Klare
Film Guy
Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003
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posted May 17, 2017 09:04 AM
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!
-------------------- 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
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posted May 17, 2017 03:03 PM
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.
-------------------- 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
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posted May 20, 2017 05:09 AM
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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