Rim Drive Reel to Reel

[Chuckie]

Has anyone worked with 3" rim drive r2r's? What I would like to know is: 1) is speed change linear or curved?, 2) what was the nominal ips for those machines?, 3) Do you know a good starting and end point for speed change or a pre-set?

Thanks

[Craig Maier]

Although I have never worked with rim drive reel to reel tapes, the speed change is curved (non-linear). I do not know what the nominal ips was since the speed changed drastically throughout the recording. I do know that the Diamond Cut Speed Change effect is what is needed to correct it using the "curved" checkbox. That brings up a 4 point spline curve generator shown and adjusted graphically. I would recommend using a trial and error method based on the sound quality that you hear. You can preview the file until you are satisfied.

Craig

[Marc Hildebrant]

I had one in my early teenager years....

Not a very good player.

Marc

[Craig Maier]

I am guessing that they were just designed for spoken word applications like dictation, mail letters, personal diaries. Of course, if you mailed a voice letter to someone, they would have to own a similar machine to play it back. Hard to imagine that anyone would have used them for musical recording work.

Craig

[Chuckie]

Yup, I had one when I was a kid, too. Right now I have a customer with a pile of "Living Letters" from Vietnam. A blast from the past.

[Craig Maier]

Hi,

So, it is important to fix the speed problem. The speed change filter should do the trick.

Craig

[Chuckie]

I have in roughed in - well sort of. I go from about -6% to +90%, starting the machine at 3 3/4 ips. I didn't put all that much of a bend in the curve. I suppose if I were really good with math, it would be a snap to figure it out perfectly. Interesting tapes to work on and the sound is surprisingly decent. All two track mono of course. Had to add leader to the beginnings and tails, too.

Charlie

[Craig Maier]

Hi,

Maybe you can find a line frequency "note" on the tape to guide you with the settings. It will be either 50 Hz or 60 Hz. Not sure what was used in Vietnam. I think that there is a line frequency chart somewhere on this forum. Set the Spectrum Analyzer for a high fft size so that you can resolve the hum frequency accurately.

Craig

[Craig Maier]

Hi,

I just found the link to line frequencies by country:

http://www.diamondcut.com/vforum/sho...hlight=country

The chart shows Vietnam as 50 Hz. But, I wonder if the US military may have used American 60 Hz generators. I do not know.

Craig

[Chuckie]

Thanks,

But if his recorder was like mine, it was battery powered. I'm pretty sure most of them were.

Charlie

[Craig Maier]

Hi,

But - - - often there are alternating current "H" fields (electromagnetic) and "E" fields (electrostatic) that are ubiquitious an any venue having electricity. These are picked up by any tape recorder by simple proximity to said field(s). The Diamond Cut Spectrum Analyzer usually can "pluck" that signal out of the mud. Put the SA in averaging mode and you should see it after the file plays for a bit.

Craig

[Craig Maier]

Hi Again,

After you get the speed corrected properly, you can use the Filter Sweeper to compensate for the varying frequency response of the tape recording. I am guessing that the tangential velocity of the tape starts out slowly and then speeds up towards the end. Thus, the top end response of the tape at the beginning is less than it is at the end.

By using the Filter Sweeper, you can even that frequency response out to provide a more natural sound. Just as a wild guess, I might set the filter sweeper for low pass mode. I would use a start frequency of say, 7000 Hz and a stop frequency of 4000 Hz, but I really have no idea exactly what it should be as I have no experience with tapes made on these macines. Experimentation with the stop and start frequency setting for the filter sweeper would be the approach to take - - - tune it for a natural sounding response thoughout the tape play, from beginning to its ending.

At the end of the day, it sounds like an interesting project/challenge.

Craig

[Craig Maier]

Hi,

If you want, send me one side of one tape via mp3 format to dctools@aol.com. I will see what I can do with it and then report to you the settings that I used.

Craig

[Marc Hildebrant]

I do not remember the formula that relates the two tape reel speeds to each other as the tape winds from one reel (full) to another (empty), but it uses a square root sign over the two reel radiuses squared.

It's certainly not linear.

Marc

[Chuckie]

Hey, thanks for all the help. The Spectrum Analyzer put me in the ball park. I got them done and the customer is happy. There was a big kicker, though. I found that very few tapes were the same. Then I remembered from way back when, when I had one of those things that, as the batteries run down, the speed changes. Seems as though there was some tape stretching, too (he had a lot of 79 cent tapes). So I pretty much just listened to the tone of his voice and made slight adjustments to my (sort of) preset. Now off to the post office.

(not sure if I ever want to fool with them again! - well maybe)

Charlie