Would it be possible to use a light emitter and a sensor that senses the reflection of the light from the tape to accurately adjust tape speed to a constant speed like the quartz locked DD Walkmans?
In theory. I commented before that an optical mouse uses that principle. The problems are the sensors aren’t small and the extra length of tape between the head and the point where the tape is pulled would increase wow and flutter. Compact Cassettes were designed to play in a mechanism that uses a capstan which is why every mechanism from a £5 market quality personal stereo to a £1000 Nakamichi used one.
Now I am going on a guess here so what I am about to say might be nonsense, however if all that is needed is a constant measuring of a signal, why not measure the shift in magnetic intensity? The play head does that anyway so why not just take that signal and process it. Question is there isn't parts of songs that could confuse something like this.
If you were designing asystem from scratch that is what you could do. Video tapes like VHS have a control track to get the speed precisely correct {although the VCR does usea capitan). The problem is that there is no such track on a compact cassette so as suggested before the player wouldn’t know whether to play at Kylie speed or Rick Astley speed.
Actually a vision rather than an actuall attempt to build a working model. Another one trying to make the worlds smalest walkman . Just a mock up but nonetheless very interesting . Details here.
More pictures of that unique mock-up: http://d-noz.com/index.php?mid=portfolio&document_srl=2779&ckattempt=3, including size comparison with a WM-F501. Great view of the head and rollers - clearly missing are the capstan(s).
Certainly , the guy that made it admits that : " I'm making the smallest Walkman in the world just for fun . Can't go any further due to lack of technology..." , it's a sign of the times , we moved from plain CAD models to 3D printed models , personally I find it fascinating that there are still people intrigued by compact cassette culture and trying to explore the walkman boundaries.
As an artist or industrial designer some of your biggest commercial markets have pretty much dried up, audio is tiny and everyone wants the 70's look for new equipment. Phones/laptops/TVs all look the same, there's been no real design changes for years. I think 90% of cars look the same, I can't believe the auto industrial design force is more than a fraction of what it was 35 years ago. So today if you have a ton of creativity and all of these wonderful tools to actually make something "cool" you almost have to step back in time when design advancements were appreciated and even expected. I feel bad for the new industrial designers, the creative outlets keep getting smaller over the years.
The cars all look very similar these days because, they all must adhere to the same safety standards hence the designer’s creativity is stifled as they cannot stray too far.
