Tape head amplification circuit

[Mooly]

OK 🙂 Good luck with it all.

 

[rtrg]

preamp

Let's hold on here a minute. Playback heads are "higher Impedance", anywhere from below 100 millihenrys (mH) for transistors to over 600mH to better match the "older" tube circuits. They "look like" a moving magnet cartridge and need in the neighborhood of 50dB voltage gain to get their output up to an "acceptable level" to feed a line stage. Record heads typically have MUCH lower impedances (maybe 10mh) and can't be used for playback (OK-never say never - but now you need 60dB or greater and here comes a hum proboem). There is also the fact that, like phono, there was an "accepted" pre-emphasis/de-emphasis curve used (NAB/IEC) so you do have to "tailor" the response of a preamplifier to accommodate this.

From your statements, I don't know if you are referring to a reel-to-reel or cassette deck. Cheap units used a combined head - (a stereo head had four posts, two for each channel) - better units used separate heads. Since you seem to indicate that sound quality is not a problem, if you have a preamp with a phono input you could feed the output of the head into it and see what it sounds like. It won't have the correct equalization (RIAA versus NAB/IEC) but you could at least see of you have enough gain for the rest of your system.

Charles

I just finished constructing 2 open reel tape transports for NAB reels. Work perfectly. Now come the preamps. In the past I have disassembled a working deck, created an enclosure, put ALL components plus harness minus the motors, in order to marry the existing heads to the transport. Lots of work not always successful.

What I would like to do this time is find a stand alone record/playback preamp 110 volt powered with line in.out jacks and 3 jacks for the 3 heads, E.R,P. Preferably stereo even if it is 2 discreet mono units. Or a kit or even a simple circuit I can make. I realize the heads will need to be TUNED to the circuit for level and overall sound quality but I hope the circuit would have some way of doing this. The VIKING 86, 88 had removable preamp with a complete 2 or 3 head design. NO audio circuits in the transport. Even the preamp was 110 volt powered.

Any help welcome.

 

[Matitjahu]

Hi guys!

I took apart an old casette deck and want to make a tape loop echo machine, like Wem. What I would really need is help with how to amp the heads? What kind of circuit does the erase head need?

Thanks a lot!

 

[Mooly]

Most tape decks use AC erase where the head is fed with a high amplitude (20 or 30 volts or even higher) high frequency sine wave of for example 105kHz.

Cheap portables sometimes used DC erase with an erase head designed for low current DC operation (it just becomes a magnet when energised). DC erase is more noisy and leaves a background hiss on the tape but it might be suitable for your use.