Rim Drive Reel to Reel

[Craig Maier]

Hi,

Glad to hear that your customer is satisfied.

Craig

[Dan McDonald]

So with these recorders, it sounds like the quality of the recording got better as the tape moved through - since it was faster as the reel got more tape on it?

Dan

[Craig Maier]

Hi Dan,

I would guess so - - - faster tape velocity past the record head would produce a higher upper frequency limit on the recording. Of course, that tape linear velocity would increase as the take-up reel filled up with tape (ever increasing effective diameter of the take-up reel).

Craig

[Dan McDonald]

Fascinating stuff. Were all the battery powered recorders before the capstan rim drive or was this something special?

I had a small open reel when I was a kid, but I don't remember the speed changing drastically, except as the battery died down.

[Craig Maier]

Hi,

I do not know - - - all the machines that I had or worked on were capstan driven. I vaguely recall seeing some friends with the rim drive machines, however. I never used one or repaired one, so I am not familiar with them. I can imagine that the recordings must have been quite poor.

Craig

[Chuckie]

As an aside, don’t be surprised if you run into a 4” rim drive. On the machine I had when I was a kid it was simple to modify it to take the larger reel. All I had to do was remove the head cover. I had it in the early 60’s and as I recall, it had one head for both recording and playback. The erase head was a permanent magnet. It was a lot of fun.

[Craig Maier]

Interesting - - - I wonder if they used AC or DC bias in the recording circuit. Do you know?

Craig

[Chuckie]

From the research I have been doing the last fews days, most were DC. There were a LOT of makes.

[Dan McDonald]

Is this the kind of 60hz signal you would see with a rim drive? It is a mono recording from 1963. It sounds a bit fast.
The top line starts at 62.2Hz and ends at 63.3 Hz, 23 minutes later.

[Craig Maier]

Hi Dan,

I am not familiar with rim drive reel to reel recordings. However, I would guess that the motor speed would remain relatively constant assuming that the batteries had not been drastically depleting during the recording process. Thus, the take-up reel speed would also have been relatively constant. So, if the take up reel speed is constant, then the tangental velocity of the tape would tend to increase as the take-up reel filled up. So, if that is true, then I would think that the 60 Hz signal would do the opposite if played on a regular capstan based reel to reel player (60 Hz would decrease as the tape progressed in time). But, the spectrograph shows the opposite, so I am not sure about it. Maybe the batteries were failing during the recording creating the opposite effect. At any rate, I am guessing that the speed could be reasonably corrected with the non-linear speed change filter.

[Dan McDonald]

Hey Craig -

Thanks. Yes it's not difficult to correct. I just get curious about these. So a rim drive would sound slower if transferred with a standard machine. I was thinking this was probably batteries. I had a small battery open reel when I was a kid,and battery drain was noticeable
very quickly.

[Craig Maier]

Hi Dan,

I guess it could be the discharge curve of the batteries creating that 60 Hz contour, especially if those types of recorders were real power-hogs (guessing that they probably were).

Craig

[Craig Maier]

I would imagine an early reel to reel portable rim drive recorder would be very power hungry; it would probably draw much more power than a cassette recorder due to the amount of motion involved and the higher mass of the tape. Also, the amplifier circuits from those early days would not have been as efficient as those found in the early 70s on portable cassette machines.

Craig

[dmfoos]

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