Re: Good Ole Fashioned tape looping

[pk@mainstring.win.net (Pat Kirtley)]

Someone commented that analog tape, and the sonic characteristics of tape
delay have a unique quality that is difficult to simulate with digital
electronics. This is true, and there is nothing like the real thing.

It isn't difficult to begin experimenting with analog tape looping. First,
go to a pawn shop or similar source and obtain a used tape machine. The
best likely candidates for looping modifications are machines with
3-head 3-motor design and electronically operated transport controls. Many
excellent and rugged machines of this type were made in the 70's and early
80's by TEAC, Tascam, Pioneer, Revox, and Akai. If you find one of these
formerly very expensive units, you will probably be able to purchase it
for $200 or less. They are now aging, but the best ones were built to last,
and can become completely operable with minor maintenance and cleanup.

There are two ways to modify the machine into a looper. Way 1 is to add
another playback head, separated from the record head by a significant
distance. Way 2 is to increase the tape-distance between the existing
record and play heads. Way 1 is described here.

If you observe the tape path, you will note that the tape is fed out
by the supply reel on the left side, first passes across the erase head,
then the record head, then the playback head, before entering the capstan
/ pinch roller assembly, and then is wound onto the takeup reel on the
right. It is not necessary to use an actual "loop" of tape to create the
audio looping function, because the audio loop is formed electronically by
feeding part of the playback head's output into the recording input.  The
concept that creates musically useful loops is a relatively wide
separation between the record and playback heads.

The easiest way to do this is to get another playback head, preferably
from a junked tape recorder (i.e. cheap). Take the playback head and mount
it on a board along with two of the tape guide-posts from the junked tape
recorder. The guide posts are necessary because the tape must cross the
playback head in a very precise alignment in order for this to work. 

Open up the head assembly on the the working tape recorder and disconnect
the wiring from the rear of the playback head. You will need a small
soldering iron to accomplish this. If you don't have one, get a techie
friend to help out. You will need to obtain a length of cable similar to
the cable you have disconnected from the playback head. It will probably
have 4 conductors and a braided shield. Ten feet is a good length to start
with (too long a cable will cause audio problems). It's got to be shielded
cable. Connect the new wire to the remote tape head, and splice to the end
of the wire in the good tape recorder. You must make sure that the
connections from the rear of the new tape head go to exactly the same
wires as the original head did. 

Position the remote tape head assembly on a solid support some distance
away from the tape recorder, to the right and at the same level as the
transport deck. Doing this works best if you have the tape recorder on
its back on a tabletop. The tape feeding out of the capstan/ pinch roller
goes out through the first extra guide, across the remote playback head,
through the second guide, and back onto the takeup reel.

You can test the new setup by putting a pre-recorded tape in place, and
listening to the output. Note: because you have altered the tape path
significantly, the machine will not work correctly in fast-forward and
rewind modes. To use these modes, remove the tape from the remote head
and let it feed through the machine normally.

To begin looping, you must establish an electronic path from the tape
machine's output to its input. The easiest way to do it is with an
external mizer. Simply include the line out of the tape machine as one of
the inputs to the mixer, and connect the mixer's output to the tape
machine input. 

You will have created a true stereo looper, and the loop-delay time is
regulated by the distance from the record head to the remote playback
head. At a tape speed of 7.5 inches/sec, 10ft of separation translates to
16 sec loop time. 5ft = 8 sec, et cetera. Cutting the tape speed in half
doubles the loop time (just like digital!). An added benefit is that your
looping creations are automatically and permanently recorded for you. 

Aside from a couple of days of scrounging around pawn shops, the project
should take only a few hours to complete. Hope this inspires some new
musical ideas, alone or in combination with modern effects/ devices. 


Pat Kirtley