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Re: [ARSCLIST] cassette crackle

I had a number of cheapo cassette decks in the early days since I never regarded the medium seriously (still don't). One was an AM-FM radio/cassette recorder with a mic (not a built-in!) which I got for obtaining a Shell Credit Card. Most of them were thirty-dollar jobbies, all had automatic gain control, and most of them made recordings that sounded pretty noisy when played back on good stereo decks. The professional portables Sony (and others) made were better in this regard, as I recall, but you'd still want to play only one channel from any of these cassettes just to ensure proper phasing (or play them back from the machines they were recorded on, if possible).


joe@xxxxxxxxxxx wrote:
So perhaps only one machine was defective?

joe salerno

Mike Hirst wrote:

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.

Best Wishes

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: 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.

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