Well, there is another partial explanation.
Use a machine set for 3.75 in/s at 50Hz and use it on 60Hz, you'll make a
recording at about 4.5 in/s made with 3.75 in/s EQ.
I saw one of these on paper tape in the Provincial Archives of
Saskatchewan. I didn't realize it at that time, but it seems like the
most logical explanation. Fortunately, that tape had low-harmonic
60Hz hum on it, so I line-locked my oscilloscope and tuned the speed for
a stable 60Hz. I got 4.4 in/s as the "proper" speed with that
method, and that's within 2.2% of theoretical which is pretty good, all
I did a quickie table
If you used a 60Hz machine on 50Hz mains, then the tape recorded at the
following speeds will play back at the second speed in the
This requires a machine that can shift downward by 16.7%
Repeating the same exercise, but with a 50Hz record machine run on 60Hz
mains, you get
This requires a machine that can shift upwards by 20%
Now, none of these sequences explains the 5 in/s in Don Chichester's
email and 5.63 in Marie's original post, although this does explain the
4.4/4.5 in/s of the Saskatchewan tapes.
Also another point to ponder. I believe some early portable tape
recorders used spring-wound motors and mechanical governors for the speed
This is distinct from the horrid "rim drive" machines from the
1960s -- which make all 3-inch reels suspect. No capstan at all, just a
motor on the takeup reel and a rheostat in series between the battery and
At 04:33 PM 3/4/2004 -0500, you wrote:
years ago a friend sent me his reel tape collection of interviews he had
made while doing a religious news show on the BBC. He asked only
that I might convert one or two tapes to cassettes for him. Upon
playing the tapeS! I found they were, in fact, recorded at about 5 ips!
I did the best I could at the time by increasing the size of the capstan
until it came close to c. 5 ips.
Evidently some recorders (for radio use???) recorded at 5 ips, or nearly
so. Else, why were there several such tapes?