Freshly produced azimuth alignment tape for your VIC anyone?

[pixel]

Last time I checked there're no such things like square waves on a tape. Am glad that we agree that it can be done.

It was considered a convenience package with perfect recording. Am really losing all motivation.

[eslapion]

Last time I checked there're no such things like square waves on a tape.

My oscilloscope disagrees with you...

[groepaz]

I suppose all you need is a tape that carries a recording of a nice square wave that's just a bit above the cut-off frequency of the low-pass filter of the playback stage. Something like 3kHz should do the trick.
Of course, you gotta make sure this tape is recorded with a tape deck that has studio quality alignment but that's something a lot of specialized audio/music shops can do for you at a small fee.

normally you'd just use the tape that you want to read and then align the head to it, no need for a special recorded reference tape.

My oscilloscope disagrees with you...

physics dictate that the signal on tape will never be a square wave. it may not be a nice sinus, but certainly nothing like squarewave either.

It was considered a convenience package with perfect recording. Am really losing all motivation.

i'm still not sure if i understand the intend aligning your datasette to a "perfect" reference only makes sense if you are planning to record tapes for others to read - if you want to read existing tapes, you always want to use that exact tape as a reference and align the head to it, IMHO.

[eslapion]

Awrite... here's what I learned about the datasette when I studied it inside and out last year...

When recording, the RW head is directly connected through the output of a Schmitt-trigger via a pair of 10kOhms resistors so only square waves can be recorded. Also, because of the type of RW head and the resistors, if you use tapes other than type I, you'll get junk recordings. Type II (CrO2) and type IV (metal) require much stronger signals and a different magnetisation

On playback, the signal is amplified but it is also passed through a bandpass filter/integrator analog circuit which flattens anything that's not in the proper frequency range. Signals in the proper range are turned into triangle waves with the amplitude of these triangle waves being the highest at around 2.6kHz. A DC offset is added to this signal to bring it between 0-5V and it is then fed to a schmitt trigger which sends it to the VIC/C64/C128/PET computer.

Tape accelerators like Compute's Gazette Turbotape are very sensitive to misaligned heads specifically because they use a higher encoding frequency and the amplitude of the triangle waves is reduced by the filter. Head misalignment reduces the amplitude of the signal even further.

Unlike floppy drives where head alignment is purely relative (if you only read your own disks then you can create your own alignment), datasette head alignment is absolute - if your head is misaligned then you won't be able to read back your own tapes or will have serious trouble doing so.

On a disk drive, head alignment only affects the diameter of the tracks. On a tape drive or music tape deck, it affects how well positioned the head is on the tape. If you record partly off the tape then you're effectively recording junk.

[eslapion]

normally you'd just use the tape that you want to read and then align the head to it, no need for a special recorded reference tape.

False for the above mentioned reasons

physics dictate that the signal on tape will never be a square wave. it may not be a nice sinus, but certainly nothing like squarewave either.

All "square" waves really are trapezoids because of bandwidth limitations. If you read a tape with datasette recorded data on it using a music tape deck - which isn't fitted with the bandpass filter/integrator of the datasette - you will get a nice square wave with the highest harmonics at around 15kHz.

i'm still not sure if i understand the intend aligning your datasette to a "perfect" reference only makes sense if you are planning to record tapes for others to read - if you want to read existing tapes, you always want to use that exact tape as a reference and align the head to it, IMHO.

False again. The head alignment on a datasette or any tape deck is absolute, not relative.

Added edit: A really badly aligned head on a datasette can damage the edges of the tape.

Added edit: I can provide scope captures to prove the above.

[beamrider]

I was thinking that one of these with a special crafted wave file and software would be pretty useful?

Assuming they are correctly aligned, which I guess is easier than a moving tape.

http://www.ebay.co.uk/itm/Retro-Car-Tel ... SwNSxVXtXl

[edit: I've ordered one to experiment with - see how it works out with the two datasettes that won't load pulse.]

[edit-2: I note that it's stereo, maybe that will be an issue?]

[eslapion]

* azimuth alignment tape with manual

What kind of signal did you intend to put on that tape ?

I was thinking that one of these with a special crafted wave file ...

[edit-2: I note that it's stereo, maybe that will be an issue?]

Just make sure the MP3 file you're playing back with it is mono.

[pixel]

I'd have used a sine wave for starters and experimented with snippets of different frequencies.

IMHO both intentions are right: you want to align the head to the tape you want to use. Having some kind of datassettoscope program would be nice for that, wouldn't it?

And you want regular alignment if you intend to make tapes for others. But then again I wouldn't use the datassette for that anymore in order to get it right down to the CPU cycle and to get a cleaner signal and a head alignment that is probably OK.

[Boray]

Unlike floppy drives where head alignment is purely relative (if you only read your own disks then you can create your own alignment), datasette head alignment is absolute - if your head is misaligned then you won't be able to read back your own tapes or will have serious trouble doing so.

Interesting!

[Boray]

Unlike floppy drives where head alignment is purely relative (if you only read your own disks then you can create your own alignment), datasette head alignment is absolute - if your head is misaligned then you won't be able to read back your own tapes or will have serious trouble doing so.

Interesting!

Does this mean that "load-it datasettes" are completely useless, except maybe for a one-time adjustment?

[pixel]

@beamrider: am afraid i've made the terrible mistake of not applying enough volume to the first batch.

[groepaz]

Unlike floppy drives where head alignment is purely relative (if you only read your own disks then you can create your own alignment), datasette head alignment is absolute - if your head is misaligned then you won't be able to read back your own tapes or will have serious trouble doing so.

not quite. programs like that head azimuth program linked before only exist because back in the days everyones datasette was differently misaligned and reading someone elses tapes pretty much required to realign each and every time. you can very well read your own recorded tapes fine with a datasette that is so misaligned that it wont read original tapes anymore. or the other way around. and if that doesnt sound familiar, then you probably just didnt swap too many tapes with others back then

[majikeyric]

@beamrider: am afraid i've made the terrible mistake of not applying enough volume to the first batch.

I still couldn't make my Pulse tape loading correctly.

I'm waiting a new 1531 to give it a try.

And if it doesn't work, I will dump the .TAP file on tape with my C64SD Princess.

[beamrider]

@beamrider: am afraid i've made the terrible mistake of not applying enough volume to the first batch.

Not to worry, I can record over it with the Princess.

I'm assuming the .tap file you provided has the correct volume (assuming .tap files describe volume)?

[eslapion]

not quite. programs like that head azimuth program linked before only exist because back in the days everyones datasette was differently misaligned and reading someone elses tapes pretty much required to realign each and every time. you can very well read your own recorded tapes fine with a datasette that is so misaligned that it wont read original tapes anymore. or the other way around. and if that doesnt sound familiar, then you probably just didnt swap too many tapes with others back then

I never had problems like that with original tapes or tapes recorded with the normal Commodore datasette protocol.

It did occur with homemade recordings that used Turbotape. This protocol made it necessary to have very accurate alignment for the reasons I mentioned earlier.