This is topic optical stereo from a Holmes? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Bruce McGee (Member # 131) on 07-11-1999, 12:56 AM:
When I was in 35 professionally, it was at a drive-in that had 20 year old equipment. That was 1975-1979. Here's the question:
IF I install a pair of solar cells side-by-side in my Holmes so each will see only one stripe of the dual soundtracks will I have a simple stereo sound system?I have several stereo prints, and trailers. Also I have plenty of time on my hands to experiment.
What do you folks think?
Bruce
Asheville, NC
Posted by Brad Miller (Member # 2) on 07-11-1999, 02:13 PM:
"Technically" yes, but fair warning the sound will probably not be too good if you are home constructing it. I can't imagine how that could be mounted in a variety of projectors and actually work properly.I've never worked with a Holmes, but if you call your local cinema parts supply dealer they might have an actual solar cell and bracket assembly for around $100-150 you could just pop in and then do an A-chain on. Better yet, if you can afford it, go with a reverse scanning LED kit. Although I doubt Kelmar or Component Engineering has gotten to the Holmes projector kits yet.
The $100-150 kit would be well worth your time and frustration in trying to figure out how to home make a stereo pickup.
ASCs number in Dallas is 214/265-9303. Roy Lisenbee is the man to talk to at extension 822. If it's out there, he can order it for you.
Posted by Ken Layton (Member # 133) on 07-11-1999, 03:26 PM:
The key to it would be getting the solar cell close enough to the film, otherwise you'd get crosstalk. Get a raw stereo Kelmar cell and make a bracket for it. It would be nice if there were a "universal" reverse scan kit we could adapt to a bunch of different machines.
Posted by Bruce McGee (Member # 131) on 07-11-1999, 09:42 PM:
The current cell is mounted in a 4-pin tube socket, and is in the exact position that the old PE cell was. There is nearly 1 3/4" of space between the film sound gate, and the face of the cell. I can remove the cell cover and remove the solar cell from the socket, and put a piece of white paper in there while film is running. I can clearly see the 2 tracks on the paper. I started wondering about this when I ran my first stereo print on the Holmes. It sounded like I was hearing an out of phase recording. When I adjusted the solar cell position more to the center between the 2 tracks, I noticed how the fidelity changed for the better.
This machine was in pieces when I got it. I found that I could use an 1156 auto lamp, and a 12v DC supply for the exciter. I have run about 30 hours of film on it without blowing a lamp. The DC supply handles the hum in the filament perfectly. The solar cell came from a junked Eiki 16 machine.
I used an SMPTE audio test film that I found on the net to focus the optics. Having good results so far.
There's more than enough room for 2 cells installed side by side. Is the left channel on the sprocket side of the soundtrack?
Is it obvious that I am on a major "restricted" budget? I am the owner of a 250 watt tube power amp that is in Newport News, VA, but I have no way to get it here to western NC except to drive 7 hours. My job requires too much time for a trip...
I appreciate your sharing of knowledge and your help. Now, if I had 2 running Holmes... Just a dream for now.
Bruce McGee
Posted by Greg Mueller (Member # 17) on 07-12-1999, 09:27 AM:
I can pretty much assure you that CE will not be producing reverse scan kits for the Holmes. I had a Motiograph sound head on my first setup and I had a Kelmar stereo cell in it. I didn't care much for the mount system they used so I built myself a 3 axis adjustable dovetail mount that I did like. I would imagine that would be possible with the Holmes as well, but I don't think I've ever seen a Holnes so I don't know for sure. I'd get my hands on a Kelmar cell and attack it from that angle.
Posted by Bruce McGee (Member # 131) on 07-12-1999, 09:31 AM:
Any idea what a Kelmar cell might cost, and where to get it?
Posted by Greg Mueller (Member # 17) on 07-12-1999, 09:35 AM:
Oh yah, the problem with using 2 seperate cells is getting them close enough together (physically) to read the track in the same place on the film. You can't get them close enough on a horizontal plane that's for sure. The only other way would be vertically and that would mean that you would have to stack them ahead and behind each other in time. That would give all your films the dubbed Italian effect, which might be interesting but not desireable.
Posted by Aaron Sisemore (Member # 145) on 07-12-1999, 12:22 PM:
Bruce:You can get the solar cell unit ( with a bracket, though as others have said I doubt you'll find one that will drop-in to a Holmes) from any cinema equipment dealer. Another point to consider is that these cells will be going to be positioned close ( within about 1mm) to the film so the cells-in-an-old-phototube-socket trick won't really work (the cells themselves are quite small). You might have to get a different slit lens for your soundhead if yours has a large slit in it. The ones with smaller slit sizes give MUCH better sound quality. You will need a basic set of Dolby test films to get the alignment spot-on as well ( you can 'wing it' for this but I have found that to get it truly right the first time, the test films are necessary. These films are also available from a cinema dealer.) Good Luck!
Aaron
Posted by Ken Layton (Member # 133) on 07-12-1999, 01:52 PM:
Ask around at the cinema dealers. You don't have to buy a brand new cell, a used one will do. With all the stereo cells being pulled out and replaced with reverse scans, I don't think it would be much of a problem to pick up a used one cheap.
Posted by Brad Miller (Member # 2) on 07-12-1999, 04:20 PM:
Ken, what a wonderful idea! Actually, I've got one I pulled out of my JJ when I converted to reverse scanning you are welcome to have Bruce. You will have to take a knife and CAREFULLY cut into the hot glue strip to retrieve the full length of the leads, but the actual cell can be easily removed from the large bracket with an allen wrench. Send me your mailing address to my private email at Flix@film-tech.com and I will ship you the cell. Hope you can make it work. Be sure and let us know here what you find. There may be someone else out there who will want to do the same thing with another Holmes!
Posted by Bruce McGee (Member # 131) on 07-12-1999, 05:03 PM:
Thanks, Brad, for the offer. I will even attempt to take pictures of the contraption when I get it installed. Our local theater supply is 100 miles away in Charlotte.A Holmes is not "professional grade" by far, but THIS one is still running after 50 years!
Posted by Bruce McGee (Member # 131) on 07-17-1999, 01:54 PM:
I have received the Solar cell. I have to install it right up against the film at the slit? This may be a major problem as the Holmes doesent have a per-say sound drum like you guys are used to.I figured out the wiring fast enough. But, I mayhave to go with the twin cells installed inside the old PEC enclosure similar to what I have now.
I would like to thank Brad Miller for sending this cell assembly to me. I will keep thinking about how I can do this using this cell. Right now, all I can come up with is the 2nd cell beside the one I have. I need to ask one more time: Is the left channel on the left side of the soundtrack on the sprocket hole side?
More News to Come, if anybody is still interested...
Bruce McGee
I had a chance to get a Super for good money a few months ago. I should have taken it.
Posted by Brad Miller (Member # 2) on 07-17-1999, 04:35 PM:
Right channel is closest to the edge of the film. Left channel is closest to the picture.I hope you can make that cell work. Did you take it off of the bracket? Good luck.
Posted by Ken Layton (Member # 133) on 07-17-1999, 05:03 PM:
Bruce:
Have you given thought to using a fiber-optic "Light Pipe"? That way you could put the end of it up against the Holmes' sound gate hole and 'guide' the light right to the surface of the stereo solar cell.
You could probably take a light pipe from and old Bell & Howell 16mm sound drum or see if Dolby can get you one from a Cat 700 reader.
Posted by Gordon McLeod (Member # 33) on 07-19-1999, 10:57 AM:
The old Phillips FP20 and FP7 used glass light pipe and there should be some of those still kicking around with the conversions to LED's taking place
Posted by Bruce McGee (Member # 131) on 07-20-1999, 06:35 AM:
Naturally! it figures. I would buy the machine that is like no other. On looking at a Dolby optical track on an old print that I just bought, I notice that there is a slight difference in the left and right track placement on the film. I mean, one starts about 1/8" before the other. When I was doing the coarse alignment of the sound optics, it was impossible to use this film and get any decent sound quality. There was no "happy medium." Is a Dolby trait? I dont have the bucks to shell out for the decoder unit that I obviously need.
I am looking around the house here to see what I might have that I can use for a mounting surface for a pair of solar cells placed inside the PE cell cover the way the current set-up is done. I removed the cell that Brad gave me from the holder. I held it in place with a pair of needlenose and it tests a bit better on my meter than the cell I am using at this time. Hopefully, I can use it.
I appreciate all the ideas that I am getting here.
Unfortunately, I have to make a living for a few weeks, and I cant do much on this subject, but I will do what I can...
Bruce McGee
Asheville, NC
Posted by Ken Layton (Member # 133) on 07-20-1999, 01:20 PM:
Bruce:
The stereo (SVA) optical track is recorded 45 degrees out of phase.It should be possible to get an old Eprad Starscope (or Starlet) or Smart or Ultrastereo for next to nothing from some of the cinema supply dealers to use with your Holmes.
If you feel really ambitious, how about coming up with a Dolby Digital basement reader setup for the Holmes!
Posted by Gordon McLeod (Member # 33) on 07-20-1999, 05:02 PM:
The SVA track is not recorded 45 degrees out of phase.
L is encoded into lt in phase
r is encoded into rt in phase
c is encoded into Lt and RT at .707 each in phase
The squirly part is the surrounds
They are recorded 180 degrees out of phase ie
Lt contains in phase surround
Rt contains the surrounds 180 degrees out of phase
On decoding the decoder uses + and - 90 degree phase shifts to extract the constant components and then feeds them to a side chain to generate the gain riding coefficients
The 45 degree phase shifts are only used for the surround ex encoder
Posted by Bruce McGee (Member # 131) on 07-21-1999, 01:30 PM:
Since the only theater supply house near here is 100 miles away, and I have to work here, I hope to find something here from you fine people that I might use. The Holmes is ill-equipped for many modifications. This one has the take-up reel on the front of the machine below the lens.
If anybody wants to see what one looks like, before the paint-job, just E-mail me personally, and I will send a picture taken a few months ago.Bruce McGee
Asheville, NC