The topic says that all. What are cassette tape dropouts (what you would hear) and why are they caused?
Dropouts are where the replay level (the signal) from the tape literally drops out.
A scope clearly shows the effect (record and playback a 1KHz tone and look at the level... it will be bouncing around to some extent) and it is caused by irregularities in tape to head contact and also defects/damage/variations in the oxide layer of the tape itself.
A scope clearly shows the effect (record and playback a 1KHz tone and look at the level... it will be bouncing around to some extent) and it is caused by irregularities in tape to head contact and also defects/damage/variations in the oxide layer of the tape itself.
All right, that is the problem I face with many tapes from the 90s. Thanks for explaining this. I was looking for a term to describe it to people when mentioning this problem.
And I have noticed that these dropouts can be caused at some points on one channel only, for a few seconds, then back again playing ok.
When calibrating the deck for correct bias and level on a tape (R+L channels separate on my deck), on some tapes (not all, and irrelevant to the tape type) the level and bias is bouncing instead of being steady at the point I set them. This happens the most on the beginning and on the end of the tapes.
Even worse, there are variations throughout the tape length, so you need to reset the bias and level at dome points.
Could my observations related to the tape dropouts?
Can sealed tapes have this problem as well?
If the tape to head contact is marginal then you will see differences between tapes and different over qualities of tapes.
One check you should do is to confirm the back tension is correct... however that needs a special test tape to perform that test. This one also measures the take up torque.
One check you should do is to confirm the back tension is correct... however that needs a special test tape to perform that test. This one also measures the take up torque.
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It is possible that some debris from the tape was sticking to the head, and later on it got rub off by the tape itself. Some older Ferro tapes have a tendency of sticking to everything.
I can't even imagine how expensive this is, if this can be found at all. So I am afraid this is not an option...
However, related to the spacing, I notice the head goes really deep into the tape when playing, I do not think it is imperfect contact. After all the deck is an expensive 3-head one with non-rotating head.
A couple of thoughts:
Because the wavelength of high frequencies is shorter, spacing loss affects HF far more than LF. So if all frequencies are affected, it's a tape oxide problem, not contact.
Head contact is ensured by the pad and by back-tension. The back-tension is created by a slipping clutch/ brake on budget decks. The better decks had twin capstans with a system to create a tension differential, such as different size pinch rollers.
Because the wavelength of high frequencies is shorter, spacing loss affects HF far more than LF. So if all frequencies are affected, it's a tape oxide problem, not contact.
Head contact is ensured by the pad and by back-tension. The back-tension is created by a slipping clutch/ brake on budget decks. The better decks had twin capstans with a system to create a tension differential, such as different size pinch rollers.
Does it happen on new good quality 60 minutes tapes, like TDK SA-X C60 or AGFA Stereo Chrome C60? If not, then see my explanation earlier. Also clean the head with a cotton swab moistened with ethanol before the test.
Mine has different size pinch rollers (teac v-5010) and because these dropouts are noticed not only on the highs and because these are noticed randomly on some tapes on random points onto the tape, I think this matches more the tape oxide problem you mention.
It is also there on some points on metal tapes I had bought new back then. These were played on decent quality deck, no hi-fi- but not rubbish. Do you think this might cause the problem, or the storage conditions? The tapes were always kept inside the house, in a closed enclosure, stored vertically, but of course there is no way to know the humidity and things like this.
I haven't got any new tape nowadays. However it is there at random points even on my old metals. By old, I mean 90s.
Other tapes, even chrome, may show no such signs. It seems to me this is purely random. Note that the appearance of these tapes I mention is great, even at the points this happens. It is only at the beginning and the end of the tape that I see the "classic" blobs (mountains) into the tapes, even metal ones. So I do not count these.
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