Film-Tech Forum ARCHIVE: Can stereo reverse reader be hooked to mono system?

This is topic Can stereo reverse reader be hooked to mono system? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Brad Allen (Member # 470) on 01-05-2004, 03:58 PM:

I need to temporarily hook the output from a stereo reverse scan reader to a mono system. Can this be done without problems?

If so, any tips greatly appreciated.

Thanks

Posted by John Anastasio (Member # 607) on 01-05-2004, 05:37 PM:

I can't imagine any problems as long as you keep both channels in phase.

Posted by Sam D. Chavez (Member # 1841) on 01-05-2004, 08:45 PM:

Reverse scan readers can be hooked to mono systems but there are some gotchas. Most mono systems have some sort of 50 Ohm or so input loading resistor meant to swamp the solar cell in order to obtain flat frequency response. Sometimes it is the mono system's volume control that forms the load.

If not removed, there is very little signal from the output of the reader so you will end up running the mono system wide open.

You may also run into some grounding issues, every case is different.

Posted by John Anastasio (Member # 607) on 01-07-2004, 06:56 AM:

Check the input with an ohmmeter and if the level is a problem, I'd use a small preamp. I agree about the grounding issue. You might have to fiddle with it.

Posted by Brad Allen (Member # 470) on 01-11-2004, 12:50 PM:

Would anyone be so kind as to explain further about what "grounding Issue's" I may encounter?

Also, please explain further on the "in phase issue".

Thanks for the help!

Posted by Gordon McLeod (Member # 33) on 01-11-2004, 01:51 PM:

The outputs of the reverse scan reader are balanced in that the -and th + are neither tied to ground
Most Mono systems were an unbalanced input so the - side is tied to ground
This can cause a lot of hum and noise when the reverse scan is connected as such
You may want to get a pair of high quality matching transformers

Posted by Frank Angel (Member # 248) on 01-11-2004, 03:29 PM:

Underline "high quality." I tried to use a Inovonics 4trk preamp unit designed for RTR tape transports to Simplex penthouses. Needless to say, what should have worked in theory (the numbers were correct) sounded like:bs:.

There is a wide range of transformer quality out there; buyer beware.

Posted by Gordon McLeod (Member # 33) on 01-11-2004, 03:38 PM:

One of the problems you would have encountered with that inovonics is the response curve of it as it would have probably been based on the NAB characterisitics not the CCIR or the SMPTE curve also the head impedance would have been an issue as that unit would have been designed for a high impedance head and the film heads for Commag prints are extrememly low impedance
If memory serves they typically are designed to reflect into a 30 ohm load

Posted by Brad Allen (Member # 470) on 01-12-2004, 10:47 AM:

Ok, this is beginning to sound like something I shouldn't even attempt.

Thanks all for outlining the pitfalls.

Posted by Gordon McLeod (Member # 33) on 01-12-2004, 10:37 PM:

There are many transformers out there a 600:600 ohm one is all you need and the bandwidth of a kono system is so restricted it doesn't have to be the best one either
Mouser has them for telephone coupling (hell they are the one s used on most music distribution amps)