klein@ucbcad.UUCP (03/27/85)
A while back there was a discussion about cassette decks and head alignment. Someone mentioned that Nakamichi was the only manufacturer to align them right. A friend of mine has an older Nak deck that I have used on occasion to record albums. I also have an auto-reverse car cassette deck, which works by reversing the direction of the tape and switching its input to the other pair of gaps in the head. What I have noticed, only with the tapes recorded on the Nak, is that one play direction always sounds much better than the other. I have tried to align the angle of the car deck's head to sound better (it was definitely out of alignment from day 1). It is easy to do this while the tape is running, as there is a cutout that exposes the adjustment screw. The result is that I can never get both directions to sound good. This implies to me that the Nak deck's head angle is not perfectly perpendicular to the tape. If it were, I would be able to align the car deck's head perpendicular to the tape and both directions would sound fine. This is because while recording on the Nak you must physically flip the tape over, so any leaning of the record head is reversed on the other side. The tape will look like this: ---------------------------------------------------- \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ //////////////////////////////////////////////////// \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ //////////////////////////////////////////////////// ---------------------------------------------------- If I align the car deck's play head to sound good for one direction of the Nak's tape, it will expect a tape that looks like this: ---------------------------------------------------- //////////////////////////////////////////////////// //////////////////////////////////////////////////// //////////////////////////////////////////////////// //////////////////////////////////////////////////// ---------------------------------------------------- When it switches direction without physically flipping the tape, the signal read is the integral of infinitely many signals all out of phase. At certain frequencies, response (ideally) will go to zero. This sounds really bad. This problem does not seem to occur with commercially prerecorded tapes, although they are not of the same quality as the home-recorded ones and it is difficult to compare. After all this, what is the problem? Is the Nak correctly aligned and does that mean that auto-reverse decks are no good? Or does it mean that this particular Nak deck is very poorly aligned? Or something else? -- -Mike Klein ...!ucbvax!ucbmerlin:klein (UUCP) klein%ucbmerlin@berkeley (ARPA)
saf@clyde.UUCP (Steve Falco) (03/28/85)
> After all this, what is the problem? Is the Nak correctly aligned > and does that mean that auto-reverse decks are no good? Or does > it mean that this particular Nak deck is very poorly aligned? > Or something else? Some comments: first, the tracks on a cassette are not interleaved they way they are on reel-to-reel, so your pictures should have been: ///////////////////// ///////////////////// ///////////////////// ///////////////////// \\\\\\\\\\\\\\\\\\\\\ ///////////////////// \\\\\\\\\\\\\\\\\\\\\ ///////////////////// Next, I think the thing that NAK worries about is that tape in a cassette deck isn't guided very well. In fact, there are a few tiny tabs of metal on the heads for all the guide functions (shown as > and <): ------- ------- >| | | |< | | | | >| | | |< ------- ------- The tape can weave around a bunch so turning a tape over doesn't guarantee it is still perpendicular. Don't forget, tape isn't perfect, the width varies a few thousanths yet the guides must be wide enough for the widest sample of tape so it can skew around differently in one direction than another. Also, tape is allowed to be slightly warped rather than straight: ------------------ ------------------------- ------------- ---------- ------------------ ------------------------- ------------- ----------- perfect warped (exaggerated) Altogether, you can see where the medium is not 100% transportable to different machines. Note, this gets much worse as the tape gets wider because a given error angle has more width to diverge in: narrow wide (more divergence) | / | / | / | / | / | / |/ | / | / | / | / | / | / | / |/ Steve Falco
ben@moncol.UUCP (03/28/85)
>A while back there was a discussion about cassette decks and head alignment. >Someone mentioned that Nakamichi was the only manufacturer to align them >right. A friend of mine has an older Nak deck that I have used on occasion >to record albums. I also have an auto-reverse car cassette deck, which >works by reversing the direction of the tape and switching its input >to the other pair of gaps in the head. > >What I have noticed, only with the tapes recorded on the Nak, is that >one play direction always sounds much better than the other. I have tried >to align the angle of the car deck's head to sound better (it was definitely >out of alignment from day 1). It is easy to do this while the tape is running, >as there is a cutout that exposes the adjustment screw. The result >is that I can never get both directions to sound good. > >This implies to me that the Nak deck's head angle is not perfectly perpendicular >to the tape. If it were, I would be able to align the car deck's head >perpendicular to the tape and both directions would sound fine. This is >because while recording on the Nak you must physically flip the tape over, >so any leaning of the record head is reversed on the other side. The >... >This sounds really bad. This problem does not seem to occur with >commercially prerecorded tapes, although they are not of the same >quality as the home-recorded ones and it is difficult to compare. > >After all this, what is the problem? Is the Nak correctly aligned >and does that mean that auto-reverse decks are no good? Or does >it mean that this particular Nak deck is very poorly aligned? >Or something else? First of all, I think you misunderstood the recent articles on the Nak decks. Nak does not align their heads differently than other manufacturers, they use a different equalization curve. As a result, tapes recorded on a Nak and played on another deck will have noticable high frequency rolloff. Second, although it is possible that the Nak has a head alignment problem, it is almost certain that your auto-reverse deck does. The problems stems from the cassette itself. There is almost always play in the guide rollers that control the tape path: they tend to slide to one side of the pin when the deck is playing forwards, and to the other side when it is playing in reverse. This kind of azimuth error would certainly be noticeable, particularly if you use budget tapes. Nak is well aware of this problem, they solve it in one of two interesting ways in their auto-reverse decks. In the inexpensive decks, they have motorized cassette drawer that removes the tape and physically turns it over. In their more expensive decks (as well as their car decks), they use NAAC, a computerized system that analyses azimuth error and uses servo motors to perform a head alignment as you listen. Ben Broder ..vax135!petsd!moncol!ben ..pesnta!moncol!ben ..ihnp4!princeton!moncol!ben
prophet@umcp-cs.UUCP (Dennis Gibbs) (03/28/85)
<> >A while back there was a discussion about cassette decks and head alignment. >Someone mentioned that Nakamichi was the only manufacturer to align them >right. A friend of mine has an older Nak deck that I have used on occasion >to record albums. I also have an auto-reverse car cassette deck, which >works by reversing the direction of the tape and switching its input >to the other pair of gaps in the head. > >What I have noticed, only with the tapes recorded on the Nak, is that >one play direction always sounds much better than the other. I have tried >to align the angle of the car deck's head to sound better (it was definitely >out of alignment from day 1). It is easy to do this while the tape is running, >as there is a cutout that exposes the adjustment screw. The result >is that I can never get both directions to sound good. > >This implies to me that the Nak deck's head angle is not perfectly perpendicular >to the tape. If it were, I would be able to align the car deck's head >perpendicular to the tape and both directions would sound fine. This is >because while recording on the Nak you must physically flip the tape over, >so any leaning of the record head is reversed on the other side. The > . > . > . > >After all this, what is the problem? Is the Nak correctly aligned >and does that mean that auto-reverse decks are no good? Or does >it mean that this particular Nak deck is very poorly aligned? >Or something else? >-- > > -Mike Klein > ...!ucbvax!ucbmerlin:klein (UUCP) > klein%ucbmerlin@berkeley (ARPA) I am replying to your question mainly because I am under the impression that you believe that once a tape deck is aligned, then it remains in alignment forever. This is NOT the case! You didn't mention in your posting what kind of maintenance your friends Nakamichi has had, but you did say it was an older machine. Has your friend ever had his tape heads re-aligned? This should be done on a regular basis (I have mine done once a year). Just because the alignment was done correctly at the factory doesn't mean it will stay in alignment for the life of the deck. Periodic maintenance/touch ups are a MUST for optimum results! Also, I tend to say that most inexpensive auto-reverse decks have the problem you mention....I would normally suspect that at first, but you say that it only happens with tapes recorded on your friend's Nak. Have you tried taking a tape recorded on the Nak and tried it on another deck other than the one in your car? Try that and see what happens...If the other deck behaves like the one in your car, then better take your friend's Nak in and have it realigned. And while you're at it, have it optimized for the brand of tape you and your friend use.... Dennis -- Call-Me: Dennis Gibbs, Univ. of Md. Comp. Sci. Center. UUCP: {seismo,allegra,brl-bmd}!umcp-cs!prophet CSNet: prophet@umcp-cs BITNET: GIBBS@UMDB ARPA: prophet@Maryland