Electronics > Beginners

Need Help Line Out To Tape Head Level

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dellsam34:
Hello everyone first time here but I'm a subscriber to EEVBlog youtube channel.

I have a weird request:

According to the diagram attached bellow, what needs to be installed in terms of an electronic circuit that goes from a line level to a head preamp level in an effort to replace the old fashion magnetic head pulse reader with a signal generator?

I will not remove the old pickup system, I will just use a selector switch in case I need to go back to the old system (embedded in the 3.5mm jack, Shown separate for simplicity).





Richard Crowley:
You likely need nothing more than a "pad" which is two resistors arranged to reduce the signal voltage.  Perhaps best would be to use a potentiometer or variable resistor or "volume control".
That way you could adjust the level of the signal coming out of your source so that it is equivalent to what comes out of the tape play head.

dellsam34:
I was thinking about inputting the audio signal directly to the tape-head preamp but wasn't sure since the magnetic head is a passive component and the line out is an active component, Wasn't sure how an active component (line out) reacts to another active component (tape-head preamp), In other words, The tape-head preamp puts out a voltage and expects the magnetic head to modulate that voltage based on what's recorded on the tape, Can an external voltage (audio tone) modulates the tape-head preamp voltage? That's what I meant to say.

If there is no harm with two voltages getting together I probably don't need a variable resistor because I can control the volume from the app from zero to the max.

Benta:
Are you writing or reading the tape?
If you're reading, your question should be "how do I go from magnetic head level to line level".

Please clarify.

dellsam34:

--- Quote from: Benta on March 03, 2019, 07:37:35 pm ---Are you writing or reading the tape?
If you're reading, your question should be "how do I go from magnetic head level to line level".

Please clarify.

--- End quote ---

I'm neither reading nor writing, I want to get rid of the playback magnetic head, I'm not making a magnetic head preamp, there are tons of them on ebay if I wanted one. The head preamp is already there it's part of the main board. I've described what I wanted to do in details in my first post.

Here is a simplified diagram of what I want to do:



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