8mm Forum: Eiki 600 Ohm Output

This is topic Eiki 600 Ohm Output in forum 16mm Forum at 8mm Forum.

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Posted by Maurice Leakey (Member # 916) on March 16, 2015, 04:07 AM:

This posting is for owners of Eiki/Elf projectors in the SNT/ENT range who want to connect their projector to an amplifier for additional output.

You need a stereo 1/4 inch jack plug, the one with three contacts.

Referring to the tip as contact 1, the small second ring as contact 2, and the long section up the cover as contact 3, connect a screened lead to contacts 2 and 3, (the screening is to go on contact 3.)

Insert plug into the usual speaker outlet socket on the projector.

I have gleaned this from the Instruction Book but I must admit that I have not tried it.

Posted by Steve Klare (Member # 12) on March 17, 2015, 06:44 PM:

This is a balanced monaural output. It's a lot more common among professional audio equipment than consumer stuff.

The nice thing about this connection is that it removes the signal from chassis ground and makes it much easier to not get ground loops (and their nasty buzzing hum) and noise pickup when you connect up to an external amplifier. The catch is it works best when you connect up to a balanced monaural input.

When I make a cable for one of these connections I pick the end that's best grounded and connect the screen at that end and not the other. That way the screen won't wind up with ground currents flowing through it.

Posted by Andrew Woodcock (Member # 3260) on March 17, 2015, 07:37 PM:

Steve, is what you are describing typically a balanced XLR connection?

Posted by Steve Klare (Member # 12) on March 17, 2015, 07:54 PM:

I think the connection is the same, what's different is the connect-or.

This way of connecting up can get nasty! I have a mixer panel that has stereo inputs like these:

Your usual nice, docile single three conductor stereo cable has now become two independent three conductor cables (R&L): yours to confuse between channels and contribute to the spiderweb.

-does work nicely, though.

Posted by Paul Mason (Member # 4015) on March 18, 2015, 05:26 AM:

Maurice,
That's interesting. Do the Eiki instructions say whether you need to attenuate the speaker socket output with resistors to avoid overloading the amp?

Posted by Steve Klare (Member # 12) on March 18, 2015, 07:57 AM:

I have a feeling these are actually two separate outputs: 600 Ohms sounds fine for a line level output (ELMO likes this value, for example.), but if you tried to drive a 4, 8 or 16 ohm speaker through this much resistance you'd be lucky to get even a whisper out of it!

Posted by Maurice Leakey (Member # 916) on March 18, 2015, 07:57 AM:

It doesn't appear that any other connections need to be made. I quote from the Instruction Book:-

"For additional sound reinforcement the projector may also be connected to an external amplifier via the low level auxiliary line output.
The 600 ohm (unbalanced) line is available at the speaker jack when using a 3 conductor (stereo type) 1/4" phone plug wired as shown."

For 8 ohm output, contacts 1 and 2 are used, i.e., the two small end connections.

Posted by Steve Klare (Member # 12) on March 18, 2015, 08:00 AM:

So, they've configured it to do a line output or speaker output through the same jack depending on how you hook up the plug.

-that's interesting.

Posted by Paul Mason (Member # 4015) on March 18, 2015, 08:04 AM:

Thanks Maurice for the useful tip. It very much assumes the projectionist is an audio-visual technician able to do simple soldering. My soldering is unreliable but many members will have no problem.

Posted by Steve Klare (Member # 12) on March 18, 2015, 08:35 AM:

They aren't very common, but there are 1/4" plugs with screw terminals.

Posted by Steven J Kirk (Member # 1135) on April 05, 2015, 09:47 PM:

There are of course adapters made to take a speaker output and convert to line-level. I have one made by BOSS, who make car audio stuff. Works great and the quality is great. It comes with RCA plugs and free-hanging wire. It is two channel so I just wired both into a mono jack plug. I then have two mono channels to go into a hi-fi stereo amp.

http://caraudiosecurity.com/b65n-speaker-to-rca-adaptor-with-adjustment

In fact I have two. One wired to a mono jack and one wired for stereo spade and pin DIN speakers. This I use for the Beaulieu 708 machine.

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