Is this a ZX81 recording or not?

Discussion about ZX80 / ZX81 Software
willinliv
Posts: 27
Joined: Sun Jun 28, 2020 9:07 pm

Is this a ZX81 recording or not?

Post by willinliv »

Hi All,
Looking to backup/digitise my Dad's old collection of ZX81 tapes, there's probably about 30 of them, half commercial ones and the rest self recorded. Spent the weekend rigging up an old Tandberg Audio Tutor, a converter for it's DIN output through an amplifier board, into an audio recorder. I tried out with a copy of Dice from Psion software which looked nice and short and after getting levels was able to load direct from tape, and also from the recording. I'm guessing that different tapes may need different levels...

Anyway, first of his self-recorded tapes and the loading noise is a bit different from what I expected, it also doesn't load (yet). It starts off sounding like a ZX81 but then goes a lot faster for the main section, then drops again. Here's a sample https://drive.google.com/file/d/1FF65bS ... sp=sharing (WARNING: sounds loud!)

I think from what my Dad says at the beginning of the recording: "ZXDB with fastbaud 11" might be just my ears and imagination. We did have Spectrum I think later on, along with VIC20, and I wondered if Spectrum did this, but looking on Youtube it sounds different again. Any ideas? I wonder if I might encounter more like this.

Also any pointers on the recording level constructively received.

Best wishes to all, Will
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XavSnap
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Joined: Sat May 10, 2008 4:23 pm

Re: Is this a ZX81 recording or not?

Post by XavSnap »

:D
Yes.
Breakout.JPG
Breakout.JPG (53.18 KiB) Viewed 2506 times
(only 43 errors...)



https://www.youtube.com/watch?v=V9mRb1TmmB8


Cleaned wavs, but keep some errors...
Beakout_microsystemes_Fastload.zip
(270.32 KiB) Downloaded 51 times
Last edited by XavSnap on Fri Jul 31, 2020 8:41 am, edited 1 time in total.
Xavier
willinliv
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Re: Is this a ZX81 recording or not?

Post by willinliv »

Thanks Xavier - I think you've done most of the work for me there! Fastload?
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1024MAK
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Location: Looking forward to summer in Somerset, UK...

Re: Is this a ZX81 recording or not?

Post by 1024MAK »

An advert for Fastload here.

Two Fastload entries in this index

I’m sure you can google as well...

Mark
willinliv
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Re: Is this a ZX81 recording or not?

Post by willinliv »

Thanks again, just tried loading your file into EightyOne Xavier and I get the screen about 'GM's Cassette Routine', similar also on my ZX81, I can't obviously proceed beyond this point because I don't know enough about things yet.

What technique/programme do you use to process the wav file? Comparing to the original it looks like your's has been normalised and reducing the noise floor. I didn't think there was a lot about this here but I must have been using the wrong search terms bcause a lot has shown up tonight, a good thread being this one: https://www.sinclairzxworld.com/viewtopic.php?t=1014

It seems there are a few java based tools that I think automate things a bit, or processing I guess in Audacity. The programme you used to use looked like somethign intended for Spectrum games I think.

Thanks Xavier and Mark
Fruitcake
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Re: Is this a ZX81 recording or not?

Post by Fruitcake »

The Fast Loader is remarkably similar to the one here on my website.

A comparision of the machine code shows it is identical except for the displayed date and name of the cassette routine. So it appears to be an earlier version.

I don't know the history of the routine so if anyone does then I'd be keen to hear about it.

On my webpage there are details of the high speed format based on reverse engineering the code. Using this it would be possible to recover any games encoded in the format.

The filename of the program is "GMLOAD " whereas the version on my website is "RLLOAD " (note the space as the last character of both filenames).

Here are the program bytes, which exclude the filename bytes (the forum file attachment mechanism does not allow me to attach a .p81 formatted file that contains the filename bytes):
GMLOAD.p
(347 Bytes) Downloaded 47 times
Last edited by Fruitcake on Wed Jul 29, 2020 1:49 am, edited 4 times in total.
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XavSnap
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Re: Is this a ZX81 recording or not?

Post by XavSnap »

The OTLA project release build by VB81, with SAVE"BREAKOUT.FL"
BREAKOUT.FL.WAV.zip
(6.83 KiB) Downloaded 43 times
To load whith EO:
Breakout2.JPG
Xavier
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XavSnap
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Re: Is this a ZX81 recording or not?

Post by XavSnap »

To clean the signal, i had to use ZxSpectape to normalise the wavs.
Just convert the wav to a standard 44k-16bits-mono.
Stretch the wavs to the same level, and reduce the silence level to the middle of the signal.
We can "auto-correct symmetry" on the Fastload before correct the pics levels.
The red lines at the right of the panel is the viewer of all of frequency in the file.
You had to get several red strips targeted in the same values… but in this file, there is to many noise to get a clean frequency graphic.

To clean the silent level:
Spec2.JPG
Spec3.JPG
To set the same values on to top of the wav:
Spec4.JPG
Spec5.JPG
FastLoad (symmetry and wavs top):
Spec7.JPG
Xavier
willinliv
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Re: Is this a ZX81 recording or not?

Post by willinliv »

Awesome thanks Xavier will give it a try later
willinliv
Posts: 27
Joined: Sun Jun 28, 2020 9:07 pm

Re: Is this a ZX81 recording or not?

Post by willinliv »

Fruitcake wrote: Mon Jul 27, 2020 8:26 pm The filename of the program is "GMLOAD " whereas the version on my website is "RLLOAD " (note the space as the last character of both filenames).
Thanks Fruitcake - the label on the tape says GMSave. My Dad is still around so I will ask him if he remembers about the techniques he used to save stuff.
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