Hi All,

Thought I'd post up a sneak preview of some new hardware I've just about completed that will interest the C64's tape fans especially.
The pictures below are from the first prototypes which I have since scrapped and added some new features to another revision, but I thought I'd at least show the first version to gather interest (or lack of).
It does several things:
1 - Works as an adaptor for a 1531 datassette to a PET, VIC-20, C64/128 style connector, or you can use the normal 1530 datassette.
2 - Allows you to record on to a datassette from the sound output of a PC (or any audio source).
3 - Mimics the 'Play' button of a datassette when playing off the PC (new revision not shown has a pushbutton).

Point number 1 is pretty self explanatory.

Point number 2, on the PC side you use a program like Tapwav.exe to convert a .tap file in to a .wav file or wavprg.exe to play a .prg or .t64 file direct to the sound card.
With my board it shapes the sound output from the PC to a 0-5V digital signal so you can then record this to the datasette directly.

Point number 3, the idea of the play button is instead of recording the sound output from the PC to a datasette (if you don't have one) you can feed it directly into the C64 and it thinks it's getting a signal from a real datasette. So when you want to play any .tap or .t64 game off PC without recording it to tape you just do the following steps.
Shift/Run on the 64 to invoke the famous "Press play on tape" prompt, with no datasette at all connected you just press the 'play' button on my board, the 64 thinks you just pressed play on a real datasette, you then press play on the PC to start the sound output of the .wav, .tap or .prg file and the program will load in to the C64 real time as it's being played on the PC.
There is a slight glitch to this concept. The C64 will pause once it reads the file name from the tape (or from the PC in this case), you either quickly press space to skip that or I will show you how to modify the C64 kernal ROM so it bypasses the "Found xx" display. The problem here is the PC doesn't know the C64 paused to display that message and it just keeps playing the file through. If you don't press space on the C64 fast enough it will miss part of the program from the PC.

So I'll be honest, I like tapes, I like the loading screens and the turbo tape loaders. This board allows you to relive the loading screens direct off your PC on a real 64, or for the real deal, record them to tape.

I've tested it on a C64 and a C16 so I would expect it will work fine on any other models using the same datasette interface.

I am aware there is some other adaptor that does a similar thing but it requires an LPT port and game port on your PC, my laptop has neither of these and all the PC's in my house only have an LPT port, no game port, so this is a much better option IMHO.

I am thinking the price will be around the $35 - $40 AUD mark (about 25 Euro) + shipping, I need to do a final add up of all the parts on the new version to confirm this.

Hope you all like the idea

Cheers,
Ross




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Very nice!

Will it be possible to do the point 2 the other way around - to record a genuine tape to wav etc?

Thanks,
On point 2, on the PCB you see this can be done, however I removed it from the new design. Here's the reason, quote from tapes.c64.no

"Another pretty common way to transfer tapes, is through sampling it with a soundcard using a HiFi-tapedeck. DON'T DO IT!!!! It's a TERRIBLE way of dumping tapes, and the error-rate is VERY high. It's quite high even using a real datasette."

I found the same thing.
My PCB does have a connector on there for connecting the internal harness from a 1531. This means all the signals are available if you wanted to build something from that to an LPT port. I think this is currently how people dump tapes?
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That's neat. I'm not clear on what I'm seeing in the pictures though. The 1351 pass-through is obvious and the audio in seems clear but what is the black plug at the back for? What is the tall thing? What do the jumpers do? It's Monday morning and this information junkie hasn't yet had his coffee so I apologize in advance if I'm missing something obvious.
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The round black plug at the back is for the 1531 datasette so one can be used on a 64.

The tall thing is a pot, this is used to set up the switching thresholds for each bit transition from the sound card. The variable in all this is the output of the sound card, not all are created equal so that allows you to change the trigger point. I'll do some shots on a scope as to why this is needed, it will make more sense then.

The jumpers are used for two reasons. Firstly to put an inverted or non-inverted signal to the 64. I then realised this was a waste of time because both Tapwav.exe and wavprg.exe allow you to invert the output anyway. This jumper is gone on the new revision PCB.
On the updated PCB there is still two jumpers. One selects where the signal from the PC goes, to the read input to play directly in to the C64 or the write input to write it to tape.
The second jumper selects the write source, the C64 or the external signal. This is actually required more to isolate the C64 from the write line of the datasette when recording the external signal to a datasette as the C64 drives this output low when not being used.

Hope that makes sense.

Cheers,
Ross

P.S - I'm with you on the coffee, espresso by 9am or just give up for the day.
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I thought I'd revisit the explanation of the use of the pot on the PCB that sets the switching thresholds for a level transition for each bit. Hopefully the photo's help explain it.
The signal you see in the pics is the actual sound output from the PC as fed to my board, the flat line is the voltage level set by the pot that defines when the digital output to the C64 or datasette will switch states (high or low).

In the first pic the threshold is set to the ideal spot (in approx the middle of the min and max level of the incoming waveform) so each transition from high to low and low to high from the PC's sound card is seen correctly. Each time the 'waveform' passes through the threshold voltage the digital output also transitions, this is what is fed to the C64 or datasette for recording.

In the second picture the threshold voltage is set too high and will produce rubbish as the bit transitions are missed. To fix that either turn the volume up, or if it's maxed out already lower the threshold voltage pot.

It isn't overly critical where the threshold voltage is set as long as it is above the noise at the low level of the waveform and not high enough that it misses the transitions. Without a scope trial and error is the trick to setting it up. There is an LED that flashes every 128 transitions so you can see when the data is getting processed.
It will only take a few tries of recording a tape and checking it will load to find the sweet spot of the PC's volume settings and the threshold trigger pot.

I've found the sound output from my laptop is pretty clean, my desktop PC has a lot of noise (ringing) on the top and bottom of the waveform so getting the threshold level right was a little more critical to getting faultless recordings.
The laptop I just set the pot mid way, wind the volume up to 90 in Winamp and play a .wav file, that was pretty much the first test I tried and it worked.

Cheers,
Ross




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Very nice work.
I use to master my tapes via PC-out as well.
Doing so I found several issues:
when using a real tape rekorder (which you dont ;-) you may have to adjust for speed. The different Tape-Deck units I tried all ran at different speeds (quite notable in Rekorder Justage and alike).
Some sound-cards or to be precise sound-drivers interpolate!
So especially when your TAP2WAV program of choice generates 100% square-waves it might interpolate them and you may lose data! check for that (in Rekorder justage your can see that be i.e. 3 typical pulse-lengths instead of the expected 2 for TurboTape).
In that case it helps to generate sin-waves from the TAP data right away.
Also you may be able to change settings for the sound-driver.

Some sound-devices use 44.1 khz some use 48 khz, depending on your WAV data this needs interpolation in any case and might introduce errors.

AND some devices invert the signal send via line-Out. Most tap2wav programs allow you to invert the data as well, keep that in mind when things fail but the data quality on tape appears to be fine.

Do you intend to produce a small series of your nice pcbs?
If so, Id love to 'order' one ;-)

Cheers and keep it up,
enthusi
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I'll buy one.
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Put me down for one.

Thanks guys, I'll just do a small run of 20 for the time being. It's going to be a revised PCB design so it's silly to do any more than that anyway.
I'll keep you all updated as things progress.
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Cool :)
Good luck with the development.
I'd be a buyer as well :)
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Thought I might as well show the C16 , Plus/4 setup as well.
It requires two 1531's as you need to remove the harness from one 1531 to make the connection. I've got 5 of these things lying around so finding a donor was not an issue.

BTW, I cannot get Tapwav.exe to load any of the C16 .tap files I am downloading, says they are not valid .tap files. Any thoughts there?
I was hoping to test some turbo loaders on the C16 from Plus/4 world. They say "In this unique section you can find original Commodore C16/C116/Plus4 game cassette images. Each file is the real image taken from tape. Where possible we have recorded the versions to have Turbo Loaders."

Cheers,
Ross


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You may want to check the bytes in the header of the tap files.
Maybe the util you are using check for specific taps like C64 only.
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Wow, I might be interested in this, but more importantly I hope this helps get even more of those "lost" tape games permanently preserved, not to mention the benefit of making new tape media!

Sounds good to me also..

I did a bit more experimentation with playing from the datassette to the PC sound card with the intention of recording it as a .wav file. The trick seems to be the sound card. I simply cannot get a good recording on my desktop PC, however, on my laptop (which I had never tried before) I did the following which worked 100%.

Played the .tap file of River Raid out the sound card on my laptop and recorded it on the datassette. I already know this works and sure enough, it loaded back in to the 64 fine (just to confirm).
I then played that same tape back and fed it in to the laptop mic input and recorded it as a .wav. Ran it through tapclean and it cleaned it up perfect. I confirmed that by loaded that .tap file in to Vice64 and it ran fine.

So I initially thought I would remove the option to playback out of the datassette to the audio RCA socket but I think I'll leave it in now. If it means another tape somewhere out there can be preserved then it's worth it.
This means the final version I release will be able to output the datassette data to the sound card too. I'm pretty happy about this as it really completes the loop in what tape users would need from this device.

Cheers,
Ross
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Interesting Project.
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vimfuego sounds like you found yourself a real nich in the CBM market for yourself, keep up the great work.

quote of the day.
KISS: keep it simple stupid.

enjoy
Shane
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I really want one of these; let me know when your first batch is ready.

Thanks

Merlin

I'm going to make 30 initially, the PCB's and components are currently in transit. So hopefully in about 2 - 3 weeks I'll be able to ship a few.

I still need to create a PDF on how to use it, I also want to have a German version of this PDF as well, so if anyone on here could do the translation for me I'll send them a free one. I don't trust Google Translate would do a decent job.

Cheers,
Ross
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