Started by Bryce, 15:34, 08 June 12
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Quote from: Badstarr on 00:23, 16 June 12I think Bryce is quite right that the AY is producing the signal we hear on a classic CPC while loading.
10 OUT &F600,&1020 OUT &F600,&3030 GOTO 10
QuoteThe reason why music played through the system seems quieter and very degraded is most likely due to the CPC only being interested in a Unipolar signal, the CPC only needs to make a distinction between Off and On or Loud and Quiet.
QuoteAlso the baud rate would be adequate to produce the horrible version of whatever 80's classic tape you happen to try to play through it.
Quote from: ralferoo on 15:52, 16 June 12For tape output, pin D is connected to tape pin 5 (MIC), which also goes via R310 and R308 to the sound amplifier circuit above (R304 goes from that point to the op-amp input).For input, pin E is connected to the opamp that goes to the PIO, but before that, tape pin 4 (EAR) is connected via R311 and R308 to the same circuit above.
Quote from: Bryce on 17:59, 16 June 12The connection via R308 is the 5V power supply to the Op-Amps, not a signal connection
Quote from: Badstarr on 20:28, 16 June 12Hmm... So the loading sound is essentially an accident? If it is then it's a good one to make, I for one like the reassuring whistles and whines while a tape loads as I'm sure many of us here do. Congratulations on solving the mystery Bryce! Having poked around on the 6128 mainboard and not being able to find a definite link to the CPC speaker I felt sure that your theory about the AY was the most logical/likely explanation. Mind you, I see no real reason why the AY theory couldn't also work in practice, you never know maybe a similar system was contemplated at some point in the CPC design. Perhaps its a little too complicated and over engineered in reality. However it may be the sound engineer in me that likes this solution as its sort of sampling, but not, using the signal produced by the cassette to produce a a clean synthesised counterpart using another device. It kind of makes me imagine it as a way of streaming samples, I dunno, my brain comes up with these sorts of ideas occasionally and sometimes they actually work
Quote from: Bryce on 15:33, 16 June 12The effect happens because the classic CPC has shared an Op-Amp chip for the tape amplifier and the sound amplification.
Quote from: Bryce on 00:38, 17 June 12I would guess that the engineers noticed the mistake during the prototype test phase, but then decided it was actually quite cool, so they chose not to solve it. Just a pity they didn't use a similar solution on the plus. For some reason (most likely cost) they decided that the plus wouldn't have an internal speaker. To be honest, it probably did save them a fortune.Bryce.
Quote from: arnoldemu on 11:16, 18 June 12So I was correct? leakage/cross talk....
Quote from: Gryzor on 17:19, 18 June 12Anyhow, didn't other systems have loading sounds?
Quote from: Badstarr on 10:40, 19 June 12It's been a while since I have used one but I seem to remember the Spectrum had loading sounds, I would imagine that, based on the Spectrum (ehem) build quality, that this would have been a simple pass through from the cassette to the modulator.
Quote from: mr_lou on 17:43, 18 June 12I remember finding it a bit frustrating there weren't any loading sounds on my mates C64 back then. Asked him how he knew where a game began on the tape. He replied: "You can see it on the colors on the screen".
Quote from: steve on 13:05, 24 June 12Details are in amstrad action issue 90 (ram) and 91 (disk controller).
Quote from: emilen72 on 14:10, 24 June 12Where find they? Megaupload link in cpc wiki section is out... of course...edit: I have find all issue, but the scan quality is not very goodhttp://archive.org/search.php?query=collection%3Aamstrad-action-magazine&sort=-publicdateif you have good quality please snd me a pm
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