This discussion is confusing me more and more as it continues ;-)

At 06:44 PM 10/5/99 +0100, you wrote:
>The bias is to overcome the hysteresis (I'm not sure about that
>spelling!) in the recording medium. As you say, modern recorders use
>about 100KHz for the bias, the recorded audio is added to this, and

If this is so, then why when you look at the specs do they give the
frequency response of the recording head as something like -3dB at 19kHz?

Also, if I understand magnetic recording, you NEED hysteresis to make a
recording (in order for the tape to effectively retain the information, the
tape must be magnetized, which means that you are on one of the flat parts
of the hysteresis loop). The audio itself must overcome the hysteresis and
reverse it (if needed) in order to be strong enough to produce a good
recording. I don't see how adding an additional 100kHz signal helps this
process. I would assume that the hysteresis loop would be a lot more linear
at 100kHz (and have a LOT less slope than in the vertical region of the
low-freq. loop).

I just want to make sure that we're talking about the same thing: I'm
talking about the walkman that I buy at the corner store for $25, not some
high-end specialty audio recorders or digital decks.

>amplitude modulates it. The bias is usually a fairly high signal level,

How does adding two signals together (in a roughly linear system) cause one
to modulate the other?

>up to 100 volts peak to peak, and the audio is very low, only a few
>100mV. This makes it very hard to see the modulation on an oscilloscope,
>sometimes you can just see it with the gain turned up and the vertical
>shift fully one way :-).

I don't know where in a normal tape deck there would be a 100Vp-p 100kHz
supply!! I am thinking more and more that we are talking about different
things.

>--
>
>Nigel.

Sean



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| Sean Breheny
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