deterioration of cassettes

Pretty much, yes. But you might want to wind it more than once before playing it. Oh, and a silly little thing; make sure that the pressure pad is still glued on to the rear of the head channel on your cassettes. It causes very poor replay when it comes off!

Unless you're lucky enough to have a dual capstan deck that keeps proper tension on the heads *that* way.

Pretty much, yes. But you might want to wind it more than once before playing it. Oh, and a silly little thing; make sure that the pressure pad is still glued on to the rear of the head channel on your cassettes. It causes very poor replay when it comes off!

Unless you're lucky enough to have a dual capstan deck that keeps proper tension on the heads *that* way.

Well, I have an Aiwa F770 dual capstan, and this certainly helps, but the results vary rather. Some cassettes are fine without a pressure pad, but with others you can still hear the difference. Part of the problem is that this is also a three-head machine, and this always presents a bit of a compromise with the cassette case, which definitely wasn't designed with 3-head machines in mind! But yes, in general, dual capstan machines are an improvement from this POV.

I have a few 8 Tracks lying around that I need to transfer. I'll keep that in mind, but I think they are in good playing shape. Now the only thing is to dig out my old stereo to play them back on IF it still works...

The thing to check is whether there's any springiness left in the foam pads. If they don't spring back when you push them down then the foam's disintegrated behind the smooth plastic film top. I've yet to find one that didn't suffer from this...

Andrew,

I'll have to check them out before I attempt to play them. Thanks for the tip!

Not a chance on playback! If you can find a cassette that has a significant level of 19kHz on it I shall be amazed.

Perhaps SteveG will be amazed, perhaps he will amaze me with some explanation that is totally different than what I think I'm seeing.

I've been wanting to try this since reading this thread, but only recently though to do so when it was convenient. After finishing an LP recording, I hooked up my "good" tape deck. According to the manufacturer, this Denon DR-M44HX's frequency response is ‘25-20,000 Hz +-3dB (@ -20dB METAL tape)'. I have no metal tape, I used TDK SA-X.

As I mentioned in an earlier post (this thread), an FM recording direct to computer shows the 19kHz tone very clearly. Here I recorded FM to tape, then played the tape into the soundcard inputs. The 19kHz tone does come off the tape very clearly. It disappeared where I switched on the tape deck's MPX filter and reappeared where I switched the filter off.

There is a serious difficulty about determining the relative levels. I recorded at the level the manual seems to suggest for this type tape: +3dB max on the machine's VU meter, although of course the level varies constantly with the music being played while the 19kHz tone appears to be constant. I'm don't know whether the deck's input level control is part of an active preamp or if it just reduces the incoming signal level.

The real difficulty comes at playback. The volume control for the headphone jack also controls the output level of the "line" output jacks. I output to computer with that volume knob at 50% because that is where I normally set it when I used to listen to music on this deck. Recording directly to computer from FM of course gives a higher level 19kHz trace, but the difficulty is telling how much difference is due to different input levels and how much to tape loss.

What does not come off the tape is the "mirror" image I get in Spectral View with a direct-to-computer FM recording. When I record at 88.2, as I almost always do, everything below the 19kHz tone is also above it, reversed in orientation like the trees and sky reflected in a lake. That area was empty coming off tape.

Having achieved the above, I created a 30 second sweep tone in CoolEdit, 10Hz - 40kHz at -6dB, plain sine wave. I connected the tape deck in and out directly to the soundcard out and in. Recording level was set at +3dB using the lower frequency part of the sweep, and I recorded a couple complete cycles. Recording back from tape, this time I set the deck's output volume control at maximum, which registered around -6dB on CoolEdit's meters.

The Spectral View of the signal off tape clearly shows the sweep tone. Brightness starts decreasing at perhaps 7-8kHz, but the signal is still very noticeable at 35kHz and I can see a faint trace all the way to 40kHz.

I then recorded with the tape deck VU meters reading -20dB for the lower frequencies of the sweep. Throughout most of the 30 second cycle, nothing registered on those VU meters. This recording, once into the computer, can be seen clearly only up to 30kHz. (This is with Spectral View on the default 120dB range). Perhaps by setting the tape deck input level control at maximum I would get much higher levels above 20kHz?

I'm not saying this is useful for anything, although it might be useful for some kind of scientific monitoring if one had nothing better, only that higher frequencies are clearly put onto and come off tape with this deck. I have no experience to say this is unusual or common.

Not a chance on playback! If you can find a cassette that has a significant level of 19kHz on it I shall be amazed.

Perhaps SteveG will be amazed, perhaps he will amaze me with some explanation that is totally different than what I think I'm seeing.

Perhaps I should have emphasised the word 'significant' - I didn't say that the medium couldn't record it - it obviously can. In order to be significant, it would have to upset a decoder on playback. Does it do this? The real issue with the replay of an FM broadcast is the relative level of the 19kHz tone.

The answer is probably 'no,' but what does "upset a decoder on playback" mean?

The level in the source itself -- the FM boradcast -- is no longer significant to me. I used to hate to be around computer CRTs or televisions sets without earplugs, but now I don't hear them at all. Thus I hear nothing of the 19kHz in the FM either. I'm sure the level that the tape will record is at least a little less than what it receives at the input jacks, probably a fair number of dB less, so it isn't likely it could be a problem after recording. Unless perhaps there is some interaction with the tape bias tone??

The answer is probably 'no,' but what does "upset a decoder on playback" mean?

There are two possible sources of error that could be introduced by having 19kHz tone present within the Dolby B system - the first, and potentially most significant one, is that the tone could cause the level detector mechanism to 'misfeed' the filter mechanism - that's why the filter is present at the input. If you actually record using Dolby B with tone present, then the level of 19kHz tone that's recorded will be raised by about 10dB above its incoming level anyway (along with everything else above the threshold frequency), and it could potentially  upset the decode process too - although I think that this is extremely unlikely, because the head/tape record/replay frequency response will inevitably lower the recorded 19kHz level significantly.

Very few people can hear out to 20K anyway so you may not hear the 19kHz pilot tone. The 19kHz tone is there only for the receiver to properly decode the stereo signal from the radio station. This is tightly controlled so that no musical or other artifacts interfere with it.

You don't state as to whether or not the tape deck is connected through the RCA I/O on the back of the deck to the soundcard. This would be a better way of doing the test rather than using the headphone jack. If you are going from the headphone jack on the front then that small ampplifier could be the adding its own coloration to the situation. Typically the recording input levels in most decks are set lower for the purpose of not creating overshoots or distortion. Likewise the meters are not a very acurate way of determining the true level that is being recorded it is only a rough estimate.

What does not come off the tape is the "mirror" image I get in Spectral View with a direct-to-computer FM recording. When I record at 88.2, as I almost always do, everything below the 19kHz tone is also above it, reversed in orientation like the trees and sky reflected in a lake. That area was empty coming off tape.

I have observed this as well and figured it was the lower sideband of the AM L-R carrier at 38KHz not being adequately filtered off by the FM tuner.  The reason it doesn't show up on cassette is because it is too high in frequency, too spread in spectrum, and too low in amplitude.

I thought it worth resurrecting this topic briefly, to note that we've just received our first two cassettes suffering from sticky shed syndrome and requiring baking. Both were commercially released cassettes, issued by the BBC in 1982 and 1984 (but presumeably manufactured by a general tape producer). The later tape had the characteristic squeal on playback, the earlier one appeared to suffer loss of treble during playback - this was caused by a build-up of oxide coming off the tape and onto the replay head.

Both the tapes went into the baking oven for about 3 hours and were completely cured of their problems for the duration of playback and transfer.

Something to beware of...

Thanks for the warning, Andrew.

For the FWIW department:

I had an EMI cassette from 1989 that squealed with no shed.  No baking or dumping of silicone on it would make it stop.  Luckily, a rare LP version showed up on Ebay some months ago.  Bye-bye cassette.

And don't forget the pressure pads. Make sure they are there and intact.