Re: Cassette tapes
- --- In email@example.com, "Kevin" <kriceslo@...> wrote:
>I second what Herb wrote.
> Very well stated, Herb.
> And, yes, I am comfortable with a soldering iron (otherwise I likely wouldn't be here), but never studied analog design too far. I get a lot of kicks writing clever code. Used to be 8051/Z80 and others, but now C# mainly.
I'll also add that the task is a software one more than hardware.
This has been addressed many times in the vintage computing forums
more times than I date count.
The cheapest and easiest solution for audio tape formats is a trivial interface (may only be cables from the tape player the jacks) to a PC sound card and PC based software to recover and reproduce it.
This solves the problems in one place.
You can recover and reprocess marginal tapes,
you can handle multiple formats (its software),
you can archive the result,
reproduce new quality tapes,
and with the magic of the internet you can share those "tapes" with
For software there is Audacity a very flexible sound capture and editing program. This can filter, merge, and perform other
operations like speed up or slow down to compensate for media
Actually you can easily reduce the content to binary or hex data
for hand entry or you could merely save the clean audio for
recording and reproduction using CD, MP3, or other common audio
formats. This allows doing what was previously done with tape recorders IE: play the tape into the small computers audio input
and it loads it. The one twist is an ipod can index and store thousands of "tapes". Oh yes and some ipod devices can store
(record) the same programs can be written out as well and
stored in a portable format (share new or modified software).
That was not an original thought that was the result of many people
(those professional hobbyists) that have already done work on that.
This is the same basic idea that people with Vinyl music can capture
clean them up and store them in the digital realm without worrying
how to keep the Yamaha turntable going.
> --- In firstname.lastname@example.org, "thinkpast" <hjohnson@> wrote:
> > --- In email@example.com, "Kevin" <kriceslo@> wrote:
> > >
> > > Herb,
> > >
> > > I see your points.
> > >
> > > My interest is a cheap or free machine that is conveniently obtainable for use by all. That machine should be able to recover degraded tapes which may not be readable on the original hardware. The machine should be able to covert those tapes to a binary (small) representation, and also convert back to an ideal analog signal. The machine should also be able to readily read/write multiple formats.
> > >
> > > Only software fits those requirements.
> > >
> > > Now, however, if there exists someone with hardware interests that wants to pursue restoration of original and/or damaged tapes, that is even better!
> > >
> > > Honestly, I'm not sure how many tapes really exist out in the world that need saving. Any? Can someone name one? I have a suspicion that most of this is exercise and hobby.
> > I wrote a long post, but I really should use my own Web site for lectures or polemics. Here's the brief version.
> > 1) There's plenty of tapes, they turn up when collected vintage machines turn up. Here's some examples I have around:
> > http://www.retrotechnology.com/restore/dg_peterson.html
> > http://www.retrotechnology.com/restore/poly_restore.html
> > http://www.retrotechnology.com/restore/polytape.jpg
> > ...and others I have not described. Web search for "computer audio cassette tape formats".
> > When you do, you'll see there are not huge numbers of audio-tape encoding schemes, but there are "many". As analog schemes, they are not complicated. Some standards are listed at:
> > http://en.wikipedia.org/wiki/Audio_cassette#Data_recording
> > http://en.wikipedia.org/wiki/Kansas_City_standard
> > http://en.wikipedia.org/wiki/Tarbell_Cassette_Interface
> > Lee Hart's 1802 BASYS or Proteus board used one:
> > http://www.retrotechnology.com/memship/basys_sch2.jpg
> > http://www.retrotechnology.com/memship/mem_basys.html
> > (As I'm said, now I'm obliged to gather them up myself.)
> > 3) Most of this - "this" being vintage computing work - is almost all "exercise and hobby". There are very few "professional" organizations engaged in vintage computing, most of them just show stuff off. So, I don't consider "hobby" a curse word. Not everything important, is blessed by being called "professional", and not everything "professional" is important.
> > 4) I could comment on the idea of some software program as being
> > "convenient for all". We are already talking about data from computers three plus decades old. Making it WORK will be an achievement, convenience is icing on the cake. Try to leave a trail, so others can add to your work, later.
> > Analog hardware has a "convenience" of not changing so much. I can still build a 1976 op-amp circuit. Maybe you can't, so that's an "inconvenience". It's relative, and also chronological - I still use MS-DOS programs for vintage work.
> > 5) Document your work, document the schemes, document the formats. Someone else will add the next format, there's always another format. Make it easier for them to do so. If your code just produces a binary image from the audio that's faithful - someone else can write a BASIC program to pull files from it. That happens a lot, in the floppy-disk world.
> > This is kinda fun! That's a plus.
> > Herb Johnson
> > retrotechnology.com
- Hi Herb,
Surely you must have heard of the Kansas City Standard?
I read an article on it in the 70's. Some guys that met in Kansas City decided to make a standard to encode bits on cassette. I don't recall the standard exactly, but it's goal is to have 1's and 0's to occupy the same amount of tape. So they did something like 4 cycles of 2400Hz for logic 1 and 2 cycles of 1200Hz for logic 0. These numbers might not be the actual values, but you can google it.
I think I scanned this article from Popular Electronics... let me try finding it. It would be on Rich Cini's web site.
--- In firstname.lastname@example.org, "thinkpast" <hjohnson@...> wrote:
> --- In email@example.com, "Chris" <cwardell2000@> wrote:
> > Herb,
> > The files section contains a "Giant Board HTML" folder that has the Netronics documentation for the "Giant Board" which is what added cassette I/O to the ELF II. You will find the schematic which includes the cassette circuits and the binary code for the monitor program that includes cassette read and write routines.
> > C.W.
> I'm on it! Thanks. Now I have to figure out how fast the ELF II ran instructions, as that sets the rate for the 1's and 0's the cassette interface produced or reads. The docs with the Giant Board mention "like the Kansas City standard" but that may mean "an apple is a fruit like a banana". I'll add some docs and annotated code to the page linked below, maybe someone with more clues than I can help on this?