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 Forum index » DIY Hardware and Software » Circuit Bending
The magnophone up and running!
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EdisonRex
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PostPosted: Sun Jun 10, 2007 10:13 am    Post subject: Reply with quote  Mark this post and the followings unread

mosc wrote:
Vcc is usually the term used for the positive supply voltage. The values allowed for Vcc will be in the devices spec sheet. I don't know what the other initials mean.


The "cc" (or "CC") stands for "Collector-Collector". "Vss" would be "Source-Source" and Vdd = "Drain". The term originates from how to supply a transistor. Vee supplies the emitter.

A fair definition of these power supply voltage terms is, perhaps unsurprisingly, in Wikipedia, although you can also find it referred other places if you don't choose to believe Wikipedia. Now that I am reminded, I remember reading this in a Fairchild Semi catalog many years ago.

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the19thbear



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PostPosted: Thu Jun 28, 2007 3:46 am    Post subject: ok
Subject description: ok
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In my eternal quest for making a cool tape echo, I tried to record music on a harddisk ( with reel to reel tape heads) and it doesnt work... i dont know why, but there is no sound other than some digital bleeps and blops, i cant record anything on the disc.. but does anyone know what kind of magnetic material the binson echorec used??? ( looks like a metal tape. Its solid, on the edge of a solid disc.)
thanks!
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Blue Hell
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PostPosted: Thu Jun 28, 2007 9:52 am    Post subject: Re: ok
Subject description: ok
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the19thbear wrote:
I tried to record music on a harddisk ( with reel to reel tape heads) and it doesnt work...


It wouldn't surprise me when the magnetic stuff used for a hard disk is "harder" than the stuff used for tape or for floppies, so that more power would be needed to be able to record on it. The fact that you still hear the digital data on playback points into this direction. Floppies would be less troublesome I'd think.

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EdisonRex
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PostPosted: Thu Jun 28, 2007 12:03 pm    Post subject: Re: ok
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Blue Hell wrote:
the19thbear wrote:
I tried to record music on a harddisk ( with reel to reel tape heads) and it doesnt work...


It wouldn't surprise me when the magnetic stuff used for a hard disk is "harder" than the stuff used for tape or for floppies, so that more power would be needed to be able to record on it. The fact that you still hear the digital data on playback points into this direction. Floppies would be less troublesome I'd think.


Magnetic tape contacts the record/play head. Disk surfaces are separated from their head. It's not only higher power, it's a very much smaller recording channel.

I think a floppy disk might work, it's a lot closer to magnetic tape than the medium used for hard disks, even old ones.

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PostPosted: Fri Jun 29, 2007 2:13 am    Post subject: ok
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A floppy disc works fine.. i used an 5. 25 inch. c64 disc..
i dont know about the 3.5 discs.. i guess they would work too, but discs like these and normal tape wear out really fast!
i would like a more robust recording medium..
.. i was told that the binson used an aluminium tape/drum Confused ( this is not the disc itself, but the actual recording material..)


Can you even record on aluminium??sounds way strange to me!
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PostPosted: Fri Jun 29, 2007 4:53 am    Post subject: ok
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ok.. so the source was wrong. it is not an aluminium disc! Very Happy
but then, what is it???
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PostPosted: Fri Jun 29, 2007 6:15 am    Post subject: Re: ok
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the19thbear wrote:
ok.. so the source was wrong. it is not an aluminium disc! Very Happy
but then, what is it???


"No aluminium" makes sense at least Very Happy

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PostPosted: Wed Sep 12, 2012 5:59 am    Post subject: Reply with quote  Mark this post and the followings unread

I have some unused tape heads in the drawer and thinking of making a "floppy echo". Does anyone know of any good enough tape head preamp schematics? for record, erase and playback heads.
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PostPosted: Wed Sep 12, 2012 12:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

Just FYI you need an oscillator too, 40khz or more, to mix with the audio signal. This is standard practice with tape recorders, my limited understanding is that it jiggles the magnetic particles to get a better response.
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PostPosted: Wed Sep 12, 2012 12:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

ah, yes, the AC-bias!
of course, thanks for reminding.

Isn't it around 120 kHz?

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PostPosted: Wed Sep 12, 2012 12:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

The higher the better! But anything above twice the top end of the audio range (16 to 20khz) should work.
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mosc
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PostPosted: Sat Sep 22, 2012 9:34 am    Post subject: Reply with quote  Mark this post and the followings unread

JingleJoe wrote:
... it jiggles the magnetic particles to get a better response.


Laughing Let's not get too technical here, Joe.

The use of the high frequency bias oscillator was discovered by accident, just like the cosmic background radiation, at Bell Labs, by Dr. Dean Wooldridge, but nobody in Bell Labs used the term Dr. because it wasn't considered cool.

Here is an excerpt of an interview with Wooldridge:

    “The other requirement was superposed high
    frequency on the recording. You have to, at the same
    time as you are putting in your growing magnetic
    fields, to put down the sound record you have to
    superpose a high frequency bias on it. The physics
    involved there is just a little more abstruse than you
    might imagine . But...it does two things: first of all, it
    greatly reduces the amount of noise that comes
    through, and in the second place, it greatly improves
    the quality. Now, I discovered that process.

    “The way I discovered it was entirely by accident.
    I had rigged up some electronic test rig so that I could
    make various kinds of changes in my electrical
    recording techniques on some tape that I was dealing
    with. And, since my electronic wiring wasn't very good
    and I hadn't shielded some of my wires, quite by
    accident some of the output of a 20,000 cycle
    oscillator that I had going over in one corner leaked
    onto the wires that were going into the recording unit,
    and accidentally put some high frequency on it, and I
    discovered that I was getting some amazingly low
    noise and high-quality recording. I had to run it down
    and this looked like a very exciting invention


That was taken from this AES paper written by Jay McKnight AC Bias at Bell Telephone Laboratories, 1936...1939, a great short read with some fine pics too.

Full interview with Dean Wooldridge is here: http://www.aip.org/history/ohilist/4981.html but I can't quote from it because of the anal restrictions posted on that American Institute of Physics web page.

Anyway, Jingle Joe's explaination seems to be at least as good as Wooldridge's. Very Happy

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JingleJoe



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PostPosted: Sun Sep 23, 2012 1:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Very interesting to read, magnetic tape machines are going to be one of my next endeavours. I've read all about them but not built one yet, all theory no practice Rolling Eyes
So while you are here mosc, let me probe your vast knowledge; I was going to ask, what are the internal resistances of the read/write heads on the average cassette tape recorder like? If they are just an electro-magnet; an inductor with a core, then it could be very very low resistance depending on the industance. Does this mean series resistance would be required to prevent them overloading? if so, what sort of current should they be limited to?
I can foresee other problems too if they are very low resistance.

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mosc
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PostPosted: Sun Sep 23, 2012 5:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

My knowledge is not all that vast. Shocked

Unfortunately, I don't know too much about tape recorder electronics. Suggest you look up some tape recorder schematics and see what others have done.

I am more interested in forgetting about tape recorders. Wink

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PostPosted: Mon Sep 24, 2012 4:01 am    Post subject: Reply with quote  Mark this post and the followings unread

Hahaha I assumed all you oldschoool chaps grew up with them and subsequently knew all about them. Laughing I've looked up tape recorders before but I don't remember too much about them, I suppose I may have had difficulty finding them, the search continues!
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