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Topic: Will I hear anything?

Adam Martin
I'm not even gonna point out the irony.

Posts: 3686
From: Dallas, TX
Registered: Nov 2000

posted 04-03-2001 12:04 PM

Am I correct in saying (generically) that a mono cell will have two wires and stereo will have three?

Ken's right about the delicate thing ... I once had a film crash that tore the stereo cell to shreds.

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Randy Loy
Expert Film Handler

Posts: 156

Registered: Aug 1999

posted 04-03-2001 12:09 PM

Dave, I had no sound with my Simplex SPS portable 35mm projector and I did what everybody here is saying and it works fine.

The projector came to me with a cord with a 1/4" plug so I plugged it into the microphone jack on a Radio Shack PA amplifyer. When I got no sound I removed the side panel to see where the cord was attached inside. It was attached to a small board, probably a no longer working preamp, which was then attached to the solar cell leads. Upon the advice of a friend who is a projection and sound engineer, I simply removed the ends of the cord from the board, spliced and soldered them to the solar cell leads (with a resistor) and plugged back into the microphone input on the amp. Presto, glorius mono sound!

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Barry Floyd
Phenomenal Film Handler

Posts: 1079
From: Lebanon, Tennessee, USA
Registered: Mar 2000

posted 04-03-2001 12:24 PM

By looking at my solar cells (if I remember correctly) the bracket that attaches to the soundhead casing is black w/ the word "Kelmar" on the side. Attached to the tip of the bracket is a clear piece of plastic or glass. Sounds like I have mono cells in all three machines?
If Adam is correct... 2 wires for mono and 3 wires for stereo.

------------------
Barry Floyd
Floyd Entertainment Group
Nashville, Tennessee
(Drive-In Theatre - Start-Up)

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John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 04-03-2001 02:07 PM

Also, by looking at the face of the cell, you should just be able to see the two halfs (L and R.)

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Dave Bird
Jedi Master Film Handler

Posts: 777
From: Perth, Ontario, Canada
Registered: Jun 2000

posted 04-03-2001 04:04 PM

Okay, I now have my resistors (set of 680's and 220's, as have been suggested, we'll see what's best). So now, as I look at the gear side of the soundhead where the output wires connect, I can see where I need to be. There's two double-pronged poles labeled
"P E CELL" above "1" and "2" below. I'm assuming that the "2" is the common as the white wire is attached. So now, my only question is: Do BOTH wires get a resistor on their way to the mic jack?

I believe they are Kelmar's (the power supply is), can't wait to hear that glorious mono sound! I'm so intrigued to play a B/W intermission reel I have, but don't dare till I'm a little stronger on threading!

Adam, I will indeed be using a drive-in speaker, which is what I use at the cottage relaxing out on the dock! Thanks guys....

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Aaron Sisemore
Flaming Ribs beat Reeses Peanut Butter Cups any day!

Posts: 3061
From: Rockwall TX USA
Registered: Sep 1999

posted 04-03-2001 05:52 PM

>>So now, my only question is: Do BOTH wires get a resistor on their way to the mic jack?<<

The resistor goes "across" the input, i.e. one end to the hot terminal and the other end to the common or ground.

Aaron

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 04-03-2001 08:35 PM

The cell in your soundhead already has a loading resistor accross it (it is a pot mounted in the coundhead directly below the scanner)
Also the CP200 manual has no pertinenant info for this application and the HPS site has even less
In a drive in the advantage of the Smart Mod2B DI processor is that it has
1 NR for SR and A type (emulated)
2 3 issolated outputs for AM mono/Field Speakers mono/ and FM stereo

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Ken Layton
Phenomenal Film Handler

Posts: 1452
From: Olympia, Wash. USA
Registered: Sep 1999

posted 04-03-2001 08:57 PM

A mono cell will have 2 wires, Black and Red, which may or may not be in a shield. A stereo cell will have 3 wires, Red (left), Black (common), and Green (right). If you get up real close to the stereo cell, you should be able to see the green and red wires actually soldered to the face of the cell.

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Dave Bird
Jedi Master Film Handler

Posts: 777
From: Perth, Ontario, Canada
Registered: Jun 2000

posted 04-03-2001 10:57 PM

I see the resistor now in the old SH-1000 schematic (from 1941), I have a lot to learn in this area. BUT, I now have my glorious mono sound! It goes to the mic input in a cassette deck to amp to DI speaker. One heck of a hum when idle , but pretty good sound actually when the film goes through.
The hum is present whether or not the exciter lamp is on, so I think it's a ground problem (not ground at all at this point).

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Ken Layton
Phenomenal Film Handler

Posts: 1452
From: Olympia, Wash. USA
Registered: Sep 1999

posted 04-03-2001 11:16 PM

Dave:
The shield of the cable is NOT hooked up at the solar cell end. You only connect the shield at the amplifier end of the cable.

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Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 04-04-2001 12:00 AM

The solar cell should be connected as a balanced input. Do not ground the shield at both ends. Ground the shield ar the pre-amp end.

None of the wires on the solar cell should touch ground.

This may be causing your hum. (referred to as a ground loop hum).

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William T. Parr
Jedi Master Film Handler

Posts: 823
From: Cedar Park, TX
Registered: Nov 2000

posted 04-04-2001 01:11 AM

The Manual and website were a suggetion to his question about getting reading material on the fundemantals of sound and not a suggetion to his related project or equipment. I know some of the Dolby manuals have some bsaic information on how a dolby track is encoded and decoded through the matrix and this is what I was hoping to point him to. It may have been in the first generation Dolby equipment manulas CP 50 and 100 where it explained hoe the Left and Right channels were recoded and the Center and Surround channels were decoded out of the Left and Right channel.

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Dave Bird
Jedi Master Film Handler

Posts: 777
From: Perth, Ontario, Canada
Registered: Jun 2000

posted 04-04-2001 07:23 AM

I'm not even using shielded cable right now, when I get some, I'll have to think about where to ground it, it's only running to a old tape deck that has no ground (two-prong plug). Will earth (wire) do? (Of course being very careful not to "ground" to the hot wire.) Thanks.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 04-04-2001 08:37 AM

I use Belden 9451 or 9452 cable for mag and cell lines
In Canada it is available through Electrosonic in Toronto

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Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 04-04-2001 02:15 PM

Gordon's suggestion will help you.

If you are using unbalanced inputs on your pre-amp, a matching transformer would be recommended. Usually, those can be found in an electronics store.

Get a 1:1 ratio, 600 Ohms input and output.
If you do this, the loading resistor is not needed to terminate the solar cell.

Ground the 8451 or 8452 shield on the pre-amp end. If the preamp has an XLR connector, tie the shield to pin 1, the black wire from the solar cell to pin 2, and the red wire to pin 3.

If you are using a stereo solar cell, don't tie the red and green directly together. It'll load the solar cell down too much, and it may not work properly, or sound good.

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