Azimuth for analogue cassettes on a DCC machine

Hello all,

I have a little question that has been bugging me for a while; how does a DCC deal with azimuth on the analogue tapes? Is it something that needs adjusting during a service or does it somehow automatically adjust?

Clare.

Hi and Welcome.

The azimuth is very delicate and sealed (usually) with red sealant. It should never be touched.
It is advisable to no longer play analog tapes on dcc players. The analoge tapes are simply to abrasive for head vs the Chrome Video Tape used for dcc.

Ralf

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I understand how delicate the azimuth is and should never be touched, I also understand that we should not be playing analogue tapes on the DCC, this is why I also recently bought a three head analogue tape deck with Dolby S, but I do have more questions if that’s okay:

I have heard that the heads are divided in two, upper and lower, with the upper section reading the digital data and the lower reading the analogue, does the azimuth affect both or does analogue and digital have separate azimuth adjustments?

The azimuth does affect both. It will be easy to notice as dcc will either stop or have limited playback with lots of dropouts. If DCC plays fine… the azimuth is perfect.

Ralf

Welcome to the forum. That’s a good question!

You may have noticed that the heads in a DCC recorder/player are usually mounted pretty “loosely”. Unlike most cassette recorders, they are usually easy to move, even by hand. And they don’t even return to the same place when you touch them by hand. So what’s up with that?

The four pins on the corners of the DCC heads in every DCC recorder/player are the magic ingredient. They are mostly responsible for guiding the tape across the head at the exact same angle every time. The actual head-to-tape azimuth is fixed because the head is fixed at an exact angle inside the head assembly.

So though you can adjust the screws on the head assembly, those are mostly to make sure the tape doesn’t go crooked and doesn’t get eaten up by the mechanism. They are not intended to adjust the actual azimuth i.e. the angle of the head to the tape.

That doesn’t mean azimuth is not important. On the contrary; the 8 tracks of digital signals at 96000 bits per second per track require that the electronics compensate for any azimuth trouble. And you can bet that the factory was very accurate when they put the head chip into the assembly at the exact right angle. That means for analog tape at 20000Hz or less, the heads are (for all intents and purposes) at exactly 90 degrees to the tape.

So you may be concerned that that might have influence on playing back analog tapes that were recorded with decks that had a… let’s say less than perfect azimuth. But because DCC uses two of the DCC heads to play analog cassettes, and those heads are really thin (less than 1/4 of a channel on an analog stereo head), and the head gap is tiny compared to a traditional head, the actual azimuth fault of a DCC head is not really that relevant. If you really do play tapes from a “challenged” deck, the most of what you’re likely to hear is a small phase difference between the left and right channels.

===Jac

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Wow thanks, that really made a lot of sense! One thing though, I read somewhere that reading the digital and analogue information are handled by different parts of the head i.e. The digital heads occupy one half of the head surface, while the analogue heads occupy the other half, so both digital and analogue tapes can be handled by the auto-reverse head assembly. Is this the case?

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Here you can see the layout for a first Generation player.
Ralf

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Cool, are there many differences between the 1st and 2nd gen systems apart from the obvious bit rate?

Hi,
The layout is the same for all generations. Only the portables are different as they do not turn the head during auto reverse.

Ralf

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Thank you for all your replies, they put to bed some of my nagging questions :slight_smile:

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