Thanks Richard,
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.
http://www.mikehirst.netfirms.com/audio/rhclick.wav
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
playtime= 0:10.010
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:
Hello, Mike,
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:
http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.