8mm Forum: One for the Audiophiles

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Posted by Gary Baker (Member # 5862) on April 30, 2017, 04:20 PM:

First of all, sorry that my next post's another newbie request for advice but after much searching I couldn't find info related to my issue.

Only fairly recently acquired a sound projector and been making do with the in-built speaker on my Eumig S810D. After trawling through some old posts here I realised I could buy an adapter that would allow me to connect the 'out' socket to the RCA ports on my modern Yamaha AV receiver...and Hey Presto! Front audio from the speakers on my projection wall which I use as part of my 7.1 digital system. Don't even get any of the 'hum' I've heard others associate with this projector and method. The only minor issue is the analog signal is favouring the front left speaker (with some faint volume coming from the right.) Does anyone know if it's possible to spread the sound more evenly over the two speakers? Or even just direct it to the centre channel? I'm pleased as punch that I've got this working at all but you know how it is...always looking to tinker and tweak whatever improvements might be possible.

Posted by Andrew Woodcock (Member # 3260) on April 30, 2017, 04:37 PM:

Be extremely careful Gary connecting our old vintage projectors directly through to a modern home cinema digital system.
It is extremely easy to completely ruin certain components within your receiver and loudspeaker cabinets.
They are made to handle today's squeaky clean digital input sources and generally can often express a complete dissatisfaction with anything beyond this.

I'd advise you to at least fit a modern mixer in between the two from your projection table. Better still is to use a separate amplifier and speaker system of similar vintage for just your cine gear or old analogue sources.

Many modern mixing desks offer effects that will very easily allow you to create a pseudo two channel stereo clean input signal into your amplifier from just a single mono input from your projector.

Posted by Will Trenfield (Member # 5321) on April 30, 2017, 05:38 PM:

Sound advice from Andrew there. The Eumig S810D is over 40 years old. Best not to connect its output directly to today's hi-tech equipment. I connect the output from my S712D to a 25 year old, or so, music centre which is still going strong.

Posted by Steve Klare (Member # 12) on April 30, 2017, 06:12 PM:

The thing you run into with an 800 series Eumig is the output impedance of the line level signal is 50,000 ohms and most amplifiers are 10,000 Ohms looking in. When you put two in parallel you get 5,000 Ohms. When you connect them to the Eumig output you are now seeing something like 10% of the original signal level.

Then again there is the hum and the grounding problems these often have.

My Eumig and my Amp never played nicely together until I put a mixer in-between:

Adding an Audio Mixer

(It's most of the way to the bottom: just to save time!)

These panels aren't very expensive and they make the business end of the system much more flexible. I can have multiple projectors and other audio sources too. I recently added in a video player and projector ad it hooked right up.

Posted by Paul Browning (Member # 2715) on April 30, 2017, 06:16 PM:

I don't know the output or impedance of the eumig you have, but you could connect two speakers together as long as they are the correct resistance, two 8 ohm speakers connected in parallel would be 4 ohms, as long as they are the same power rating you would get sound from both. It may say somewhere on the back of the projector or if you have the manual it will probably be in there.

Posted by Steve Klare (Member # 12) on April 30, 2017, 06:22 PM:

The output I'm talking about is the DIN line level connection at the front lower corner of the machine (below the framing knob). This is what is best used for an amplifier input.

The nice thing about going this way is you can clean up the signal externally a lot easier.

Posted by Winbert Hutahaean (Member # 58) on April 30, 2017, 06:48 PM:

You guys forgot with his crucial question but more into some tech explanation [Smile]

quote:
The only minor issue is the analog signal is favouring the front left speaker (with some faint volume coming from the right.)

If your film and/or projector is mono then there is spill out from your left channel.

If it is stereo, you must understand that the stereo 2 channel in film prints is recorded on two different bandwidth due to different size of the magnetic track.

If you see the one close to the sprocket has narrower track than the one one the right (main channel).

8mm film is not meant for stereo sound. The narrower track is meant as the balance strip to make it even when film getting through the path. So film will have the balane focus on all frames.

Cheers,

Posted by Steve Klare (Member # 12) on April 30, 2017, 07:36 PM:

I think he has to turn the volume way up because of the signal reduction I was talking about.

When you do this things like hum and crosstalk and hiss become more noticeable.

-you magnify anything enough, all the flaws come up too!

The joy of using the mixer is the monaural inputs have a knob that lets you put it all in the left channel, all in the right channel, or divide it up between them any way you'd like.

Posted by Gary Baker (Member # 5862) on May 01, 2017, 10:11 AM:

Thanks all. I certainly wouldn't want to mess up my amp in any way so will take the advice on not connecting directly. Will look into a mixer as it's the kind of thing I might get some other uses out of. Cheery-ta!

Posted by Steve Klare (Member # 12) on May 01, 2017, 10:27 AM:

They are a pretty minor expense. Mine is two monaural channels and two stereo channels with a simple equalizer each and per-channel volume controls. There are also one or two very simple inputs and outputs added in which are basically just on/off.

This ran me $65. There are several simpler ones that are cheaper.

-on the other hand if you are willing to lay out the cash you can get ones with enough knobs and sliders to frighten a Rocket Scientist!

If "used" is your thing, they are on E-bay cheap as dirt, and even cheaper than potting soil.

Posted by Andrew Woodcock (Member # 3260) on May 01, 2017, 10:52 AM:

I can recommend a Numark CM 200FX for this purpose. It has a nice fx section to give you good spacial sound to your mono tracks, even in a soft furnished lounge area.
Has a basic equalizer built in also to filter out the nasties.

For anything more precise, id recommend you add in a rack mount Behringer EQ.
Both excellent value for money units.

Keep your gain low until you gain experience with any mixer settings and dont encroach the red led areas to keep the amp signal the purist it can be.

Posted by Steve Klare (Member # 12) on May 01, 2017, 11:15 AM:

-and we have to be fair here too: these aren't exactly plug and play. The "play" part is pretty easy, it's the "plug" that makes life interesting.

To get my 800 series Eumig to play nice with my Behringer mixer I needed a cable that may not exist anywhere else on this planet (at that rate the other planets aren't looking good either...): DIN monaural male to a balanced 1/4" TRS plug. (These are usually called stereo phono plugs but in this case they are used for one monaural channel.).

I have one because I bought the pieces and soldered them together. If you are of the soldering persuasion I'd be happy to describe it for you.

Posted by Martin Davey (Member # 2841) on May 01, 2017, 11:30 AM:

A sneeky workaround suggestion! With my set up I use a 3.5mm input jack on the front of the Yamaha (AV) amp. Inserting the jack fully would present you with the normal L or R choice for mono, depending on the connections between the projector and amp. However I found by accident that if the jack is slightly pulled out from the amp that the signal then comes from both the L and R. If the 'pro logic' circuit is activated then the sound is placed in to the C channel and the mono track sits perfectly with the picture. Obviously experiment with this at low levels!

Posted by Steve Klare (Member # 12) on May 01, 2017, 11:47 AM:

That makes sense!

Fully inserted, the tip is left, the ring is right and the sleeve is ground. When a monaural plug is inserted in a stereo jack, the tip contacts the left contact, but the sleeve contacts both the right contact and ground contact, so right is grounded and that channel is dead.

I think what you've done is by partially pulling the plug out, now the tip is touching BOTH left and right and ground is still grounded.

It aint the way the ship was meant to sail, but it's at least understandable.

Posted by Martin Davey (Member # 2841) on May 01, 2017, 11:58 AM:

lol, thanks for the clarification Steve!

Posted by Paul Browning (Member # 2715) on May 01, 2017, 12:12 PM:

Steve the plugs you talk of do exist, I use them every week with virtual dj, into a mixer, left and right channel connected together for deck one, same for deck two, but one phono connection in, two phono's out, into decks one and two. Works perfectly, but you only get mono sound out.

Posted by Steve Klare (Member # 12) on May 01, 2017, 12:59 PM:

Oh well, I enjoy putting this stuff together at any rate.

This may be a regional thing: there is DIN standard equipment over here, but it's usually pretty old. As a matter of fact, a lot of the time when I order DIN connectors they start out across the Pond. I did a pretty decent order from Maplins about a decade back. I'm still using it up.

It wasn't always this way. Back in my teenage years I'm pretty sure I could buy DIN connectors at Radio Shack. I didn't KNOW that's what they were: just another of many things I learned too late!

Posted by Andrew Woodcock (Member # 3260) on May 01, 2017, 02:23 PM:

The reason why vintage audio equipment works far better with our 70's cine equipment is simply because it is better matched.
Today's loudspeaker arrangements have a far higher frequency range as well as generally having far greater sensitivity for quality audio gear.
This is actually a detrimental aspect when it comes to what you actually want to hear from our projectors soundtracks and magnetic head reproduction. Even more so if using optical sound films.

The speakers of the same era and better still, those purposefully made for our machines, do by far a better job of letting us all hear only what we all want to hear and much much less of the things we don't!

Posted by Will Trenfield (Member # 5321) on May 01, 2017, 06:08 PM:

Very true, Andrew. As speakers age, their performance can increase but this is cancelled out by the frequency range of our own hearing decreasing with age!

Posted by Gary Baker (Member # 5862) on May 02, 2017, 10:30 AM:

A true wealth of knowledge and tips. Thanks Guys!

Posted by Gary Baker (Member # 5862) on May 14, 2017, 06:05 AM:

Okay, so I invested in a basic but bitchin' Behringer mixer and now my sound is nicely balanced across the front speakers. I even found the DIN monaural male to stereo phone jack that Steve described. Sorted!

I can now enjoy my cine film and perhaps avoid blowing up my shiny new amp. Also as I'm projecting onto the same wall I use for my HD cinema I get the best of both worlds.

Thanks again for the sound advice.

Pun optional [Smile]

Posted by Steve Klare (Member # 12) on May 14, 2017, 08:16 AM:

Hi Gary,

We are glad we can help. Personally, I enjoy fixing problems this way: I don't even need to put my tools away afterwards!

If you can, please post a link to the cable you bought (even just the part number). Other people who need to make the same connection will find it useful.

Thanks!

I'm guessing your mixer is something like Xenyx 502.

What I like about these is the connectivity they allow. For example, just for laughs I grabbed a couple of cables and adapters recently and plugged my IPhone into mine recently and played music through my stereo: very easy and it worked fine. (-we all get laughs in our own way!) Recently my son needed to listen to a talk from a website and write a report for school. Once again: a couple of cables and adapters and my laptop was playing through my stereo.

We don't actually use these the way they are intended. We don't often mix multiple channels, but select one and control its volume. Maybe we should call them "choosers" and not "mixers"!

Posted by Gary Baker (Member # 5862) on May 14, 2017, 12:50 PM:

You're spot on about the Xenyx502; that's precisely the unit I went for.

I also enjoy playing around with this stuff as I find it very therapeutic (when I'm not tearing my hair out). Presumably if I were to get a stereo capable projector this bad boy could handle it no problem. The tinkering possibilities are endless.

I got the cable from Amazon UK. Here's the link:

[URL=https://www.amazon.co.uk/kenable-3-5mm-Stereo-Audio-Cable/dp/B003OSNVC4/ref=sr_1_1?ie=UTF8&qid=1494787355&sr=8-1&keywords=5+Pin+Din+MIDI+Plug+To+3.5mm+Jack+Stereo+Plug+Audio+C able]Amazon[/URL]

[ May 14, 2017, 02:00 PM: Message edited by: Gary Baker ]

Posted by Steve Klare (Member # 12) on May 15, 2017, 09:17 AM:

Gary,

Your cable is subtly different from what I have. Just for the sake of discussion here's the difference:

Yours:
Pin 2: Sleeve
Pin 3: Ring
Pin 5: Tip

Mine:
Pin 2: Ring
Pin 3: Tip
Pin 5: (not connected)

What you have is an unbalanced stereo DIN to 1/8" phono plug.

Mine is a balanced monaural DIN to 1/4" phono plug. (no adapter)

What difference does it make? In your case none at all. In the setup you have right now it is performing well and for the gain in performance you've made it sounds like £2.18 (with free shipping!) well spent.

There may come a day when you connect in some other piece of grounded equipment (another projector, for example) and all of a sudden you will notice hum in your speakers. This is because you've connected two pieces of grounded equipment and as a result of the difference in the qualities of the two grounds you are now running current back and forth in the grounding line and the resulting voltage is getting added into your audio signal. It shows up in your speakers as hum. (Eumig 800s are notorious for this.)

The balanced connection isolates the different grounds and puts a stop to this.

Carry on Projecting! Enjoy yourself, but if you ever run into this problem, just remember this thread.

Posted by Gary Baker (Member # 5862) on May 16, 2017, 07:29 AM:

Okay, so NOW I hear the hum!

I don't know why I didn't before. It's possible I was just so delighted to successfully redirect the sound at all that I was deaf to the problem. Anyway, 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. I've not soldered much more than the odd resistor to LED lights for model display purposes, but I reckon I'm up to it.

Posted by Andrew Woodcock (Member # 3260) on May 16, 2017, 07:40 AM:

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

Posted by Steve Klare (Member # 12) on May 16, 2017, 09:11 AM:

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!

Posted by Steve Klare (Member # 12) on 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!

Posted by Gary Baker (Member # 5862) on May 17, 2017, 01:03 PM:

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.

Posted by Steve Klare (Member # 12) on 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.

Posted by Ken Finch (Member # 2768) on May 19, 2017, 01:25 PM:

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]

Posted by Steve Klare (Member # 12) on May 19, 2017, 01:41 PM:

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.

Posted by Andrew Woodcock (Member # 3260) on May 19, 2017, 01:49 PM:

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?

Posted by Gary Baker (Member # 5862) on 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.

Posted by Ken Finch (Member # 2768) on May 20, 2017, 06:42 AM:

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]

Posted by Andrew Woodcock (Member # 3260) on May 20, 2017, 07:15 AM:

Ok thanks Ken.

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