Last year, I got 2 identical cassette player/recorders, which are also sometimes called cassette dictaphones from eBay. The model is Panasonic RQ-L335 (mono, to keep it less complicated). They work fine except for noticeable humming noise given out via the monitor, but that is acceptable for this project - I want to embrace any defects from these obsolete technology. I removed the doors from them for exposed tape loops. For the audio cassettes, I use 2 Maxell UR-10’s. I have a set of specifically-for-cassette splicing tools, including a splicing block, a splicing tape, and a few razor blades, which helps the construction of the loop a lot smoother and cleaner.
Below shows the path (the RHS of the screw driver) along which the magnetic tape will travel, out of the cassette shells. The arrow indicates the approximate place where the tape is guided out.
To start off, I remove the transparent sheet on inner walls of both sides of the cassette that help retain the tape. Then, trim the transparent part of the tape away and trim the whole tape away from the 2 reels. The reels can be saved for later purposes, if not used in this project.
Looking close at the shell, we can see there is a block (left, red box), that means, I have to modify the shell as well. P.S. The cassette must be side A up, or the components will easily fall apart. The blocks indicated by yellow lines are cut out (centre). (The result (right) is not so smooth though…)
Up next is the loop. Normally if we make a single compact cassette tape loop, the length of the magnetic tape itself and thus the playing time in one cycle, are very limited. On the other hand, with an exposed, extended tape loop travelling from one cassette shell to another, it is possible to make it very long, albeit at a high risk of breaking the tape for the compact cassette tape width is merely eighth of an inch. However, for this particular project, I would like to make the distance between the dictaphones not too long, nor for sure, too short. I first tried to build a loop making a distance of 50cm, which I think is appropriate. The loop length can be assumed in such calculation:
a: ~6cm, b: ~9cm, d=50cm, so the approximate loop length is 142cm. I decided to round it down and keep it to 140cm.
The thin magnetic tape is very hard to handle in order to measure to get a long piece. I first indicate the distance of 140cm on the floor with sticky memo. Then the magnetic tape is straightened out using sticky memo every few centimetres. The memo is not so sticky that it won’t damage the tape when I remove them.
Then I transferred the tape to the table to continue the job - to make a loop. Sticky memos are used again. Although it does help with the process a lot, I still need extra helping hands to get the loop into the cassette shells.
The resulting distance in between is slightly under 50cm. Putting the loop onto both dictaphones and straightening it out, I find the result satisfactory. I think I will stick to that.
As I have expected, the tape is bent. The dictaphones need further slight modification in order to prevent damages to the fragile tape. Also, the exits from the cassette shell need to be made narrower & smoothened so that the tape stays in place easier. Hot glue may help.
The tape runs smoothly when both machines are spinning the motor. I think no adjustment to the motor speed is needed. I also tested how the dictaphones records & plays. A dynamic microphone is used for the recording one and the playback one just uses its internal speaker. Since the microphone can record the sound from the playback from a certain distance, there are some clear feedback. Meanwhile, it also records new sounds from the environment, which is what I wanted. Overall, I think the effect is quite satisfactory. From the video, we see that it takes about 15 seconds for the tape to travel from one tape head (record, ~0’19”) to another (playback, ~0’34”). I think the delay is also acceptable.
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