I have no information as to what equipment was used. However, it is my
suspicion that small mono machines were used. I have digitised some 600+
tapes over the past few months. Only a small percentage exhibit this
fault. I think what I need to do is to look at the transfers again and
establish what factors are common to those recordings which have
crackle. I suspect they are all mono recordings and using only the left
channel would be a workable solution.
It's odd. I sit in a darkened room listening to these things day in and
day out. After a while these little glitches start to really get to you.
Reading the messages on this board helps keep me sane. Keep up the
good work guys.
David Lennick wrote:
> Dumb question (for various reasons, I can't listen to the file at the
> moment). Were these cassettes all recorded on small mono portable
> machines? Tapes made on these almost always have a crackly or noisy
> right channel when played back on good decks and in stereo. The solution
> here is simply to play only the left channel.
> Mike Hirst wrote:
>> 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.
>> 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: [log in to unmask]
>>> Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
>>> Detailed contact information:
>>> Quality tape transfers -- even from hard-to-play tapes.
16 Ocean View
Tyne & Wear
tel: 0191 289 3186
email: [log in to unmask]