Interference from cassette player
in [UK Mac]
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From: Rowland McDonnell on 18 May 2010 06:07 Woody <usenet(a)alienrat.co.uk> wrote: > Jaimie Vandenbergh <jaimie(a)sometimes.sessile.org> wrote: [snip] > > That it's on the recording is not too surprising - it just means that > > the wires on the source side (ie anywhere from the tape head to the > > A-D converter in the Mac) are being affected. > > > > Probably easiest to turn off your mobile, plus any 3G data devices you > > might have lurking around (GPS, iPads, 3G data USB things, whatever). > > And remember that the head of a cassette player is a coil of wired > designed for picking up tiny magnetic variations. A mobile phone signal > is massive to it. The designers knew that, which is why they're all shielded. Okay, can't be shielded all round, there is still pick-up. But... With sound earthing, you should be okay if the phone's half a house away. Rowland. -- Remove the animal for email address: rowland.mcdonnell(a)dog.physics.org Sorry - the spam got to me http://www.mag-uk.org http://www.bmf.co.uk UK biker? Join MAG and the BMF and stop the Eurocrats banning biking
From: Woody on 18 May 2010 06:28 Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > Woody <usenet(a)alienrat.co.uk> wrote: > >if it is a mains loop, > > Earth loop, you mean - via the mains wiring is the usual way it happens > in domestic audio. Earth loop, yes. I can't remember if the iMac actually uses the earth though. I guess I should have looked when I had mine apart. I know the macbooks don't. -- Woody
From: Adrian Tuddenham on 18 May 2010 07:30 Jaimie Vandenbergh <jaimie(a)sometimes.sessile.org> wrote: > On Mon, 17 May 2010 12:54:15 +0100, Martin S Taylor > <mst(a)hRyEpMnOoVtEiTsHm.cIo.uSk> wrote: > > >Peter Ceresole wrote > >> Have you tried with another cassette player? > > > >I would, but it's the only one I own and so few people have them these days. > >I bought this on eBay specifically to transfer my tapes. > > > >I'm not sure it's a motor fault, anyhow, since the problem is reduced when I > >move the cassette player further from the computer. Would you expect this > >from a motor fault? > > Yes, a crackly motor would spit out hf interference. Do you have a > metal tea-tray you could put between the computer and the player, or a > much longer 3.5mm lead? The tea tray would need to be earthed to the computer frame so as to stop capacitively-coupled electrostatic interference as well as inductively-coupled electromagnetic interference. A ferrite ring on the audio lead might help too. Is the 'earth' of the system actually earthed at all? The question which has not been answered is whether the recorder is picking up interference from the computer or whether the computer is picking up interference from the recorder's motor. I suspect the former is the more likely, but the three suggestions above will work almost equally well in both cases.. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
From: Peter Ceresole on 18 May 2010 08:31 Woody <usenet(a)alienrat.co.uk> wrote: > Earth loop, yes. I can't remember if the iMac actually uses the earth > though. I guess I should have looked when I had mine apart. > I know the macbooks don't. I don't think it does. When I had bad hum problems, with a TiBook , I made an earth lead that went from the earth terminal of the 3mm jack to a nearby radiatpr. That sorted it nicely. -- Peter
From: Martin S Taylor on 18 May 2010 10:48
T i m wrote >> It's one of these: >> >> <http://www.maplin.co.uk/Module.aspx?ModuleNo=1170> > > Hmm, if it's actually one of those (not just looks like) then indeed > it suggests it's screened. Yes, it is actually one of those. > The only thing I'm not sure about now is the fact that the lead is > mono, (as probably is the cassette player) but the input to the Mac is > probably stereo. However all that should mean is the contact on the > 'ring' of the input on the Mac (as opposed to the 'tip' contact) would > be shorted to ground so effectively muted. > > Out of interest is it recording on just one channel ... do you have > any control over that. Left to itself, it records on one channel, but I can fix that using Amadeus. > Do you have any other things you could use as a audio source as a > test. Something with a 'line' rather than 'headphone' out would be > preferred as well. Sadly not, or I would have done so long ago. Other people's comments seem to be shedding light on a workaround, if not the actual cause. I'll report back. MST |