Vinyl to Digital
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From: Peter Ceresole on 15 Mar 2010 08:17 T i m <news(a)spaced.me.uk> wrote: > Hmm, I wonder if this sort a thing is down to experience (in that > field, like PeterC - BBC although I'm not sure he's seen said effect) Nope, even looking for it I don't see those artefacts. But maybe our TV is good that way. My son in law claims to see them, so maybe it's inherent in the person. As for hearing the whistle from CRTs; 15625Hz. It came from the line scan transformer, and was the noise of the core changing shape each time it generated the voltage to drive the beam across the screen. Of course flat screen TVs don't have those... I used to be able to hear poor quality 625 sets whistling away (good ones suppressed it in various ways) and once, at an electronics show in 1962, I walked behind a rack of 625 test gear and the noise was like having a very fine skewer spiked through my head. 405 line sets (if you ever came across those) whistled at 10125Hz- almost bass register... Now, I doubt that I could hear either 405 or 625. One curiosity was that the sets used an oscillator that ran free at a lower frequency, and each line scan was triggered by the broadcast line sync signal, a square wave that was differentiated by a simple LC circuit to give a really sharp spike at the leading edge, and that would set the scan in motion. This meant that if there was no picture signal, you'd hear the lower scan frequency, and when a picture came up, you'd hear it change. When the Beeb switched picture to another source (say a studio to an OB) and you lost picture for maybe a frame, you could actually hear it more easily than you saw it. -- Peter
From: T i m on 15 Mar 2010 08:37 On Mon, 15 Mar 2010 12:17:04 +0000, peter(a)cara.demon.co.uk (Peter Ceresole) wrote: >T i m <news(a)spaced.me.uk> wrote: > >> Hmm, I wonder if this sort a thing is down to experience (in that >> field, like PeterC - BBC although I'm not sure he's seen said effect) > >Nope, even looking for it I don't see those artefacts. But maybe our TV >is good that way. Indeed, as others have mentioned it seems it's one of those things that can vary because of several factors. It obviously *is* an issue as it's mentioned on the review Ian linked to but like with smoking, some people can learn to like it. ;-) > >My son in law claims to see them, so maybe it's inherent in the person. It would seem so. However, I'd have though (as one does when it appears obvious I guess) that everyone could see a bad example (but maybe not)? > >As for hearing the whistle from CRTs; 15625Hz. It came from the line >scan transformer, and was the noise of the core changing shape each time >it generated the voltage to drive the beam across the screen. Of course >flat screen TVs don't have those... I used to be able to hear poor >quality 625 sets whistling away (good ones suppressed it in various >ways) and once, at an electronics show in 1962, I walked behind a rack >of 625 test gear and the noise was like having a very fine skewer spiked >through my head. Sounds very much what I 'hear' 24/7 via my tinnitus. >405 line sets (if you ever came across those) whistled >at 10125Hz- almost bass register... Now you mention it I never heard the same annoying noise with them. > >Now, I doubt that I could hear either 405 or 625. You were lucky. Seems it's in the family ... daughter can hear (at a disturbingly high volume) some of these cat / other_pest repeller things. She even had an article published in the paper (but more about the Mosquito youth repellant) along the lines that it probably wouldn't be allowed if 'adults' and especially allowing the legislation could hear it. Maybe they should issue free earplugs to those innocent people who just wanted to go about their business? > >One curiosity was that the sets used an oscillator that ran free at a >lower frequency, and each line scan was triggered by the broadcast line >sync signal, a square wave that was differentiated by a simple LC >circuit to give a really sharp spike at the leading edge, and that would >set the scan in motion. This meant that if there was no picture signal, >you'd hear the lower scan frequency, and when a picture came up, you'd >hear it change. Interesting. > When the Beeb switched picture to another source (say a >studio to an OB) and you lost picture for maybe a frame, you could >actually hear it more easily than you saw it. I wonder if that was ever used as a diagnostic tool? Cheers, T i m
From: Graham J on 15 Mar 2010 08:50 "Adrian Tuddenham" <adrian(a)poppyrecords.invalid.invalid> wrote in message news:1jfe35w.1bho7su1ggefqwN%adrian(a)poppyrecords.invalid.invalid... > Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > > >> FWIW, normal old-fashioned line-in is a much smaller signal than the CD >> standard usually expected as the line level by modern audio kit that I >> come across. > > 'Professional' i.e. BBC or GPO line level is equivalent to 1 milliwatt > into 600 ohms and is called "0 dBm". This is about 12 dB below the > maximum allowable signal and gives a reading of '4' on a BBC-type Peak > Programme Meter. Measured with a voltmeter in a 600-ohm circuit it will > read 0.775 v R.M.S. It's an awful lot of money to pay for1mW into 600 ohms!!! -- Graham J
From: Adrian Tuddenham on 15 Mar 2010 09:40 "Graham J" <graham(a)invalid> wrote: > "Adrian Tuddenham" <adrian(a)poppyrecords.invalid.invalid> wrote in message > news:1jfe35w.1bho7su1ggefqwN%adrian(a)poppyrecords.invalid.invalid... > > Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > > > > > >> FWIW, normal old-fashioned line-in is a much smaller signal than the CD > >> standard usually expected as the line level by modern audio kit that I > >> come across. > > > > 'Professional' i.e. BBC or GPO line level is equivalent to 1 milliwatt > > into 600 ohms and is called "0 dBm". This is about 12 dB below the > > maximum allowable signal and gives a reading of '4' on a BBC-type Peak > > Programme Meter. Measured with a voltmeter in a 600-ohm circuit it will > > read 0.775 v R.M.S. > > It's an awful lot of money to pay for1mW into 600 ohms!!! It's not terribly expensive to build in at the design stage; but most mass-produced stuff is made without it, so you only find it on expensive equipment aimed at the real professional market (not Pro-Am). It can be a real blessing under fraught conditions when the signal must get through. Half a mile of unscreened cable strung out across hedgerows or through a theatre lighting gallery - and still no hum. ....and what price can you put on a wedding recording that would have failed if I hadn't been able to parallel the outputs of two 600-ohm mic pre-amps, confident that they wouldn't 'fight' each other. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
From: Peter Ceresole on 15 Mar 2010 10:02
T i m <news(a)spaced.me.uk> wrote: > Sounds very much what I 'hear' 24/7 via my tinnitus. Oh yes. Except that tinnitus is quite a bit louder. And rather lower frequency centred, whitish noise. Although mine is at what I am told is quite a high level, it doesn't bother me. Apparently it's not so much that some people have worse tinnitus than others (although clearly some do) but that people's *tolerance* for tinnitus varies widely. My tolerance is high; others, I was told, would be driven crazy by the same level. So it's a metter of luck. > > When the Beeb switched picture to another source (say a > >studio to an OB) and you lost picture for maybe a frame, you could > >actually hear it more easily than you saw it. > > I wonder if that was ever used as a diagnostic tool? Nah. It was always a bloody nuisance... But the general noise level in a gallery or a tech area (mostly fans and spoken instructions- 'camera three, five next, stand by Kempton OB, run telecine') was far too high to use line scan noise as much of an indicator. -- Peter |