[sdiy] Sampler with tape dump?

[Mike Bryant]

Yes I know all about these issues - I used to design ADSL and then VDSL modems which have to adapt around moving interferers, including other modems of course.   The 56kpbs 'analogue' modem speed was only on download so we could put more energy with pre-distortion into the signal at well above 3.4kHz.  This couldn't be done on upload so was limited to 33k.

Terrestrial TV depends on Trellis coded modulation and very long Reed-Solomon (RS) codes that you couldn't use in modems because of latency to get a useable signal out of the mush  These could have been applied to a cassette if they had been invented back then and you had some way of building the huge amount of logic required, but one didn't back then.


________________________________
From: Roman Sowa <modular at go2.pl>
Sent: 08 August 2024 13:28
To: Mike Bryant <mbryant at futurehorizons.com>; synth-diy at synth-diy.org <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Sampler with tape dump?

There's no more truly random medium than "the air" and still QAM64 is
doing perfectly fine there as in terrestial TV. 256 was maybe tiny
exaggeration, althogh I'd be tempted to try it hoping for really good
results if I cared anough.
Don't forget, we (as in "we, humans) have reached theoretical limit of
56kbs in lousy 3kHz bandwidth of a phone line.

Roman

W dniu 2024-08-08 o 14:13, Mike Bryant pisze:
> QAM256 (or any other such technique) depends on a consistent, almost
> predictable, level of noise.  I suspect cassette noise is truly random
> so it would drop back to lower levels, in the end a single binary bit
> and just get the speed we used to get.
> ------------------------------------------------------------------------
> *From:* Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Roman
> Sowa via Synth-diy <synth-diy at synth-diy.org>
> *Sent:* 08 August 2024 12:44
> *To:* synth-diy at synth-diy.org <synth-diy at synth-diy.org>
> *Subject:* Re: [sdiy] Sampler with tape dump?
> Using modern modulation techniques like QAM256 one could achieve much
> higher throughput from a cassete. I wouldn't be surprised to see 200kbps
> of clean data after all correction stuff, so that 128kB Commodore loads
> in like 5 seconds.
>
> Roman
>
> W dniu 2024-08-08 o 01:19, Gordonjcp pisze:
>> On Wed, Aug 07, 2024 at 02:41:38PM -0700, brianw wrote:
>>> I seriously doubt it. The dump to tape would take so long that it would probably have a 100% chance of error. The size of a synth patch versus the size of a sample is quite a significant difference.
>>
>> It depends. Home computers with as much as 128kB of RAM used tape for storage, so you could easily store an entire Ensoniq Mirage's worth of sample and program RAM to tape. Using standard ZX tape routines it'd take about 15 minutes to load or save, considerably  slower than floppy disk. Even using something like Speedlock would
> only take that down to about 10-11 minutes.
>>
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