your advice is, as ever, well informed sagely and intelligent. I
suspect that I'm not going to find a definitives answer here, but
for your interest, and for anyone else who may be interested, I've
posted a 10sec (wav) clip of the kind of crackle I'm hearing. this
sort of thing will continue through the full length of the recording
and can be heard when the tape is played back using multiple
recorders, all of which have been tested using other tapes, which
exhibit no such problems.
filesize= 1392640 byte(s)
riffsize= 1764036 byte(s)
format = Straight-PCM
channel = 2
depth = 16 bit(s)
blk.size= 4 byte(s)
smp.rate= 44100 Hz
samples = 441000
you will note from the clip that the crackle can only be heard in
the rh channel. this is typical of the phenomenon, but it can
sometimes be heard in both channels (with a bias towards the rh ch).
I have experimented with some of the de-crackle filters I use when
working with disc transfers and as Richard suggests, the crackle can
be removed, I am however curious as to where the crackle comes from.
Richard L. Hess wrote:
Tom Fine has already posted a number of good explanations.
There are, however, less-common explanations that you may wish to
be aware of, just in case.
(1) If there is a mismatch between the record machine record and
erase head track position, perturbations in the record bias and/or
erase MAY print to a tape like this. DC-(i.e. permanent magnet)
erase may also cause something like this, but it is usually more of
a "burbling" or what is sometimes called "rocks".
(2) Static electricity and PLAYBACK machine "glitches" CAN print to
a tape without the recorder being in record mode. It's uncommon
(thankfully), but it can happen. Static can be generated by fast
winding in a very dry environment, and depends on cassette
materials including the shell and slip sheets. This is more
prevalent with reels than cassettes.
This clicks can usually be removed (depending on their source) by a
declick/decrackle plug-in for your favourite DAW. The Magix
restoration tools version of this is the best I've yet owned, but I
haven't owned either DC7 nor the high-end Algorithmix version.
At 08:53 AM 2008-09-18, Mike Hirst
Here's a thing that's been confusing me for some time. I have
spent the past six months working my way through a large number of
cassette tapes mostly recorded between 1985 and 1995. every now
and again I notice light, but significant crackling. This is often
more noticeable in the right channel, but not exclusively so. On
some recordings this is louder, on most recordings this is not
evident at all. This is not restricted to any one brand of
cassette, nor is it associated with any one playback machine
and/or soundcard. Can anyone explain this for me?
Richard L. Hess email: richard@xxxxxxxxxxxxxxx
Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
Detailed contact information:
Quality tape transfers -- even from hard-to-play tapes.