Connecting a playback cassette head to a microphone preamplifier

The Tascam Porta 03 was used for this experiment.


Without doing any modification or removing any connector from its internal cabling, 2 voltmeter probes were used to get the signal directly from 1 coil of the playback head while it was still connected to Porta 03.


Signal path, setup:


The Sound of Silence (instrumentals) prerecorded cassette, Mercury - 1 coil from the Porta 03 head corresponding to 1 tape track - Canford step up transformer with primary inductance 400mH - Pleiades V4 prepreamplifier powered by 4.8 volts - Realistic disco mixer at mic input - Sennheiser HD580


It is amazing how low the signal from a cassette head is. Is it lower than a moving coil cartridge?


When the fader on the Realistic mixer was full up the VU meters never came to 0 VU.


Had a moving coil microphone be connected the needle would be going like crazy even with soft voice.


The sound lacked low bass, high treble and at midrange the responce was rising. This is expected and it is the reason we apply de emphasis to compensate pre emphasis..


There were no buzz problems as the output from the head is balanced since it is a coil.


Changing from 3 1.2V batteries to 4 for supplying the Pleiades V4 electron tube prepreamp increased the gain. There was still less than 0VU on the realistic mixer.


A higher input transformer step up ratio should give more signal.


Connecting 2 of the head coils in series or in parallel, creating one channel of 2 track stereo for the whole width of the cassette tape should double the voltage output. The other 2 head coils can create the other channel.


Increasing the running speed too should improve many parameters.


The hiss when the pause key was pressed was just like the hiss we are accustomed from top class microphone preamplifiers. But when the moving coils of the microphine capsule is connected hiss is decreased. The cassette head appeared as if it were a 10KΩ equivalent noise resistor which seems very high. Exceeds noise may be a systematic error due to connecting the head with crocodile clip cables which might have picked rf.


It is realized that the hiss we hear when using good cassette players with the pause key pressed reflects the de emphasis playback curve. There is bass noise content and high frequency noise content as expected.