This is topic Installing 4-track Mag on the CP500 in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Travis Cape (Member # 466) on 07-26-2000, 06:05 AM:
I am wanting to install 4 track in my booth. I have a CP500 with the 685 card and an MPU from a CP200. I am assuming that I can go out of the MPU and into the Aux/Mag 37 pin input. Is that correct?
Posted by Ari Nordström (Member # 288) on 07-26-2000, 10:53 AM:
Yes, that's correct. The mag input is designed for a Dolby MPU. Also, the 4-channel mag format (can't remember the format number right now) is predefined in the CP500.
Posted by Travis Cape (Member # 466) on 07-26-2000, 04:22 PM:
I just needed the reassurance that I knew what I was reading. I changed the format to #22 35MM Magnetic on the menu all ready.
Posted by Mark Gulbrandsen (Member # 72) on 07-26-2000, 07:20 PM:
Travis,
The mpu should have the latest(transformerless) preamp cards to be able to work decently with the old high impedance heads that you will most likely find in your penthouse. The older cards can be identified as they have two silver or black round input transformers on them. The late cards are transformerless. If you turn the hf eq up to where it usually needs to be set the preamp can sometimes go into oscillation!! Beware! I have had this happen with brand new old stock heads. If this happens it can ruin your high frequency drivers if you have the fader up at a normal level. Keep the fader down, and I suggest using a scope on the preamp output lines to be sure this has not happened.
I have heard very few decent sounding 4 track prints, and I have heard allot of them. They usually suffer from serious hf roll off, are noisy, and have very limited dynamic range.
Its fun to run em sometimes though if its a great film. Good luck with this.
Mark
Posted by Steve Guttag (Member # 268) on 07-26-2000, 07:54 PM:
A couple of "heads up". First, the CP-500 for some unknown reason uses a 388mV buss level for the Mag/Aux input so you will have problems achieving level. The Dolby MPU was designed around the 100mV buss level used on older Dolby processors. The 388mV thingy came up with the CP-65 only when using the noise reduction facilities...it was a poor idea then and inexcusable now. It is too late in the game for magnetic to be playing with the buss levels.Next, since 35-Mag is the enemy of Dolby SVA they didn't do a very good follow though on the 35mm mag formats. You won't get surrounds with the canned format 22 setting. They goofed on programming that format. The are feeding the surrounds with the .... Le, Re, inputs since current Dolby people think of those tracks as Left Surround and Right surround.
To work around this, you will need to create your own user format that is based on the 35mm mag format 22 but with the surround mode in the conventional setting (like 70mm).
Steve
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"Old projectionists never die, they just changeover!"