I remember when CD's were becoming common, most car stereos didn't have a CD player. There was a kludge: "fake" tape which was actually a recorder head on a tape chassis connected to a CD player which transferred the CD player output to the cassette player: https://en.wikipedia.org/wiki/Cassette_tape_adapter
Now, my idea: a tape chassis, with a recorder head, with a built in battery and SD card connector. It could play MP3's directly to the recorder head and I could use old cassette players to play MP3's!
Now, some possibilities: if it is efficient enough, it could be powered by the cassette player motor. No need to re-charge! Another possibility: it could sense the direction and speed of the motor and use it as a UI to play, stop and fast forward/backward; no need of any button!
How much power does it need? Could the winding mechanism provide the required power? Got to look up some specs on the maximum torque provided by the winding mechanism and the turning speed.
The capstan is where the maximum torque is, although the very slow rotation would need some gears in order to extract some power from a small dynamo; the tape rolls torque is very limited on purpose to barely keep the tape in tension without breaking it, and they would be unusable for this purpose. Also it wouldn't be easy to keep something in contact with the capstan to extract its energy, since the capstan/pinch-roller pair has been designed to work with tape, not pulleys or gears.
The hardest problem is hence mechanical; a repurposed small stepper motor could work great as generator, and the electronics involved beyond the standard Lithium charging chip would be minimal. But adding the necessary gearbox to this device would likely raise significantly the cost of production, which is probably the reason we didn't see it yet.
That makes sense. I agree that this is probably not cost-effective, but it could still be fun as a hobby project.
> Also it wouldn't be easy to keep something in contact with the capstan to extract its energy, since the capstan/pinch-roller pair has been designed to work with tape, not pulleys or gears.
The force could be extracted using a tape/ribbon similar to a real cassette tape, but one that loops around internal pulleys with a tensioner.
It would be probably not cost effective, but I would still be curious of the maximal power draw you could get from the capstan. I suppose we know the tape speed (2.4 cm/s according to Wikipedia), but we also need the maximal force the capstan can excess on the tape. I wonder if there are some specifications for maximal friction forces within a cassette tape to be conforming, so we can get a good guess at this.
2.4 cm/s translates to 41.7 mN / mW (millinewton per milliwatt). This is not counting for losses for converting the mechanical energy.
edit:
The force requires seems to be excessive. The lowest power draw I can imagine is ~0.1W for a BL device like this (probably generous), and then we would need 4N pulling force on the tape for that (still not counting losses), which is a lot. Anyway, this was a fun exercise.
TechMoan has a video taking this to its logical conclusion, using almost exactly the adapter you describe (a cassette format mp3 player) in a cassette to 8 track adapter inside a desktop 8 track player.
I really like the idea of using the motor as a combined power source/user interface component! As the proud owner of a 2004 sedan, hacks to get digital audio on the original stereo are a common daydream of mine.
Maybe Bluetooth low energy could fit in that power envelope too?
There are already mp3 players in a cassette form-factor, with output via tape head and 3.5mm jack. I think some of them can receive bluetooth audio, too.
It would also really drive home how much music fits on an SD card. One vital feature would be to save the current position, so you don't have to fast-forward for two hours again to find your favorite song.
Nice idea... but for those adapters, the sound quality is quite subpar as far as I know. I don't know if this can be sufficiently improved. At least, it is probably better than a FM radio transmitter.
The Walkman was cool, I had several. Then the Discman. But the coolest of all was MiniDisc—-super slim, ultra portable, indestructible media, no skipping. It was popular in Japan but niche technology in the US. I really wish it caught on. One of my favorites features was the inline stick remote with an LCD display screen. Put the player in your pocket and clip the remote to your shirt, bag, etc. with full controls and a display of the current track.
The artificial limitations around digital music kept me from being interested in minidisc. Things that made sense were blocked or intentionally slowed. Too expensive for those kinds of headaches.
The MiniDisc didn't make any sense if you were invested in CDs already. CDs have higher capacity, and 16-bit 44.1kHz sampling, which is much better than MD. MDs had more durable media, sure, but this means you have buy 2 copies of all the music you want, so you can play it both in your portable player and at home on your real stereo system. Cheaper and easier to just use a portable CD player, or dub onto cassette, or later, burn a copy onto CD-R. And CD didn't have any mechanism to prevent copying.
MiniDisc only real flaw was that it was a Sony format. The copy limitations, issues with the record labels, limited third party support, excessive price outside of Japan etc all come from there.
Otherwise outside of sampling rate (MD were ATRAC only at first), the points you raise were not an issue if you bought into the ecosystem: buying music directly in MD, playing it on your portable player and sticking it in your Sony compo would be fine. Buying blank MDs and recording, copying etc. on them was mostly fine, all of that on a format way more sturdier, stable, and convenient than CDs.
I think CDs would have "died" and get replaced with MDs if it wasn't for Sony being themselves and screwing it up.
Again, the sound quality is not the same as CD; I don't know why you're ignoring this because it's a show-stopper. Because of this, you have to buy 2 copies of everything: MD and CD. Otherwise, what's the point of having a nice home stereo system if you're going to play shitty-sounding music on it? Sure, in the car or in public you might not notice the difference, but at home on a nice system you will.
We already had a lo-fi format available: cassette. Why bother paying a lot of money to go to another format that also has lousy sound quality when you can just buy a CD?
Shitty sounding? Have you used minidisc? I honestly can’t tell the difference between CD and minidisc. I’ve even got a marantz cd/md combo that rips cds to MDs. I can play the sound sound back to back in both formats on this unit and I can’t hear the difference. This is on my Yamaha NS-200 monitors in my nice sounding room.
Mini disc sounds nothing like cassette but it has a lot of the good features like re-recording and even digital management of the tracks which is better than cassette or cd. I even have an MD head unit in my car!
I record a lot of stuff in mono as I usually don’t care for the stereo most of the time.
Yes it’s way too expensive. But I’ve got 22 year old discs that still work. It’s paying off in the long run for me.
The only issue I have is that it’s getting harder to find the gear
Why would you buy two copies of everything? You buy a CD and dub the CD onto a blank MD. It'll still sound better than a cassette by a lot. Pre-recorded MDs were a rarity even in Japan. Part of why they were so popular in Japan is they made good quality copies from the CDs you got at rental shops.
The minidisc was for many things right for portable music. The audio quality was great, indistinguishable from CD to me, and any minor detail gets washed out when riding on the train or walking on a street. CDs are great but not a portable media. They scratch, break etc. It can be hard to load a new disc when standing it in crowded places. Portable CD players were awful at skipping. The couple seconds buffer was fine for a small bump but that was it. MDs were bulletproof.
Sound quality was pretty high from the first versions. As you point out, not CD levels, but as a portable player it was good enough in comparison to what we had at the time. From there they improved the compression algos and had a lossless format towards the end.
It was easy to copy them onto blank minidiscs (with track marks and titles) when CD+minidisc units became available, I don't know far into the lifespan of the format that was though.
I had such a thing, fond memories. I had to buy a stereo set with MD recording capabilities to be able to use the small thing on the road with my existing music, but the little remote stick and the overall form factor were very nice. I remember there was some bulge on the back for an AA battery. It was a lot of swapping batteries and discs. I used it for a couple of years in between my last Discman and my first MP3 player. Music from the 'Club 2000' cd's are forever linked in my mind to this little MiniDisc player.
Ah yes, I remember the bulge! I had one with that until getting a Japanese one which had the “gum stick” sized rechargeable battery which eliminated that and say flat.
Where can I buy a thing that works in a similar way?
I'd like to give it to an elderly person to listen to audiobooks:
- one easily pressed button resumes playback from last position in last played track
- one easily pressed button turns off
- physical volume knob
that would be the minimum, but you get the idea. I cannot find a single such device:
- either the player does not remember track position (that is normal for music)
- or it is a touchscreen android device with an app
Does such thing even exist? Can it be reasonably DIYed?
I tried something similar, i.e. MP3 playback from SD card on a "small board". Because I am an electronics noob progress is slow. There's a lot to consider like SPI multiplexing when you run a display and the SD card adapter over SPI (that display/SD combo in the "tape player" project is quite interesting). First I went with some lm386 audio amp until I learned it's a lot easier with an I2S amp such as it is used in Walkm3person.
After some semi-successful attempts with a Metro M4 Express (samd51 chip) I have now switched to ESP8266 (built-in Wifi opposed to the M4). It never occurred to me that the Raspberry Pico is powerful enough for MP3 playback.
The RP2040 is proving to be a surprisingly versatile chip. The fact that Raspberry Pi Picos and similar RP2040-based boards are relatively plentiful helps, too.
Not sure why you'd want something like this. Imagine writing a book on paper, but instead of letters you're writing the binary representation of each letter. Wouldn't it be easier and more efficient to just use the paper as intended?
Just use good metal tapes, you'd be surprised with the quality (read: hard pressed to notice it's a tape). Plus, whatever circuitry you're using gives analog sound an extra bit of personality (though this isn't always for the best).
What a cool little project. It occurs to me that you could also make the opposite: a cheap portable audio recorder with a 3.5mm jack, which has a number of practical uses. I think that's doable with a chip like the TI AIC3104.
I remember when CD's were becoming common, most car stereos didn't have a CD player. There was a kludge: "fake" tape which was actually a recorder head on a tape chassis connected to a CD player which transferred the CD player output to the cassette player: https://en.wikipedia.org/wiki/Cassette_tape_adapter
Now, my idea: a tape chassis, with a recorder head, with a built in battery and SD card connector. It could play MP3's directly to the recorder head and I could use old cassette players to play MP3's!
Now, some possibilities: if it is efficient enough, it could be powered by the cassette player motor. No need to re-charge! Another possibility: it could sense the direction and speed of the motor and use it as a UI to play, stop and fast forward/backward; no need of any button!