Tape head preamp

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Here you have something to start:

http://www.qic.com.cn/qicfileserver/readFile.action?filePath=/pdf/STMICROELECTRONICS/TDA2320AN.pdf

Several years ago I made a vacuum tube cassette player using EF184 as amplifiers, and it did the job fine.

Thank you. I have some NE5532 laying at home, can I use them instead?

If you had done a search on this thread for tape preamp you would have come across;

http://www.diyaudio.com/forums/analogue-source/222113-preamp-reel-reel.html

Thank you. I was only searching for tape head preamp and didn't realize, that this is practically the same.
 
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Have you tried looking up some old service manuals of cassette decks from the 1970's and 80's such as Sony TCK5. These use simple discrete transistor circuitry running on a single rail (and the performance is superb). Or the Sony WM6DC (Nakamichi beater) portable. All easy to copy the preamps and record amps from.

Nearly forgot, you need a "bias" signal for the record head which can be DC for simplicity if needed although AC bias is far superior. 105Khz rings a bell :) Long time since I worked much on tape formats now.
 
Have you tried looking up some old service manuals of cassette decks from the 1970's and 80's such as Sony TCK5. These use simple discrete transistor circuitry running on a single rail (and the performance is superb). Or the Sony WM6DC (Nakamichi beater) portable. All easy to copy the preamps and record amps from.

Nearly forgot, you need a "bias" signal for the record head which can be DC for simplicity if needed although AC bias is far superior. 105Khz rings a bell :) Long time since I worked much on tape formats now.

I found it, but it dosent look so simple :p
105kHz is for erase head and 60-200 kHz is for recording. I think you can get better performance with a discret op amp.
 
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I found it, but it dosent look so simple :p
105kHz is for erase head and 60-200 kHz is for recording. I think you can get better performance with a discret op amp.

Your not understanding how the record process works :)

The AC bias is derived from an oscillator and "mixed" into the signal fed to the record head. Without bias of some sort (AC or DC) the record process is non linear. All you would hear on playback is distorted peaks of the signal.

Remember the AC bias isn't processed at all by the audio circuitry. It is purely an HF current added to the head to linearise the record process.

The same bias frequency is used for erase too. Its a fixed frequency :)
 
The recording head should be fed from a current source (or through a series resistor), and the frequency response of recording amplifier is flat. In some cases there is some boost at 15 kHz or so for compensating the head gap HF loss. Bias is applied directly at the recording head, after the aforementioned series resistor.
 
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Low quality portable audio (radio cassette players) often used a permanent magnet type erase head. They work but the erase is "noisy" meaning if you play an erased tape in a high quality unit the background noise is obvious. Play a tape erased with AC erase and its much quieter.

The bias for the record head is a current rather than a voltage as oshifis explained. So yes, its quite possible to have a switched bias scheme for normal/chrome/metal tapes as these all need different bias. Switching the voltage to the bias oscillator is another way of altering the amplitude if using AC bias. Like permanent magnet erase, DC bias is noisy compared to AC bias.
 
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