These experiments are without a prepreamp. Source was male singing voice at 1in.
The Tascam porta 07 has an input impedance of 50KΩ.
The output impedance of the M-55 HL at H is 50KΩ. It was loud but bass heavy. It is possibly due to the relative high inductance of the M55 HL, more than 700mH? But it may be great for recording drums for example. By eqing, the sound gets more towards flat from vocal cords of singer to listener's brain. As written on a previous post the M55 HL sounds amazing on the iPad when connected to the Pleiades K117 prepreamp. The iPad powers the K117 and the iPad-GarageBand deep low cut, about 300Hz? makes flat reproduction from vocal chords of singer to listener's brain. The sound has body.
The M55 (K) which is 500Ω was stepped up by an inline 1/4in to 1/4in input transformer 500Ω to 50KΩ ie 1:10 ratio. The input inductance of the transformer used is 300mH. The combination sounded great almost flat from vocal chords to listener's brain due to the Pleiades filter of 300mH removing the excessive bass to listener's brain.
The Sony F-96 High has a not so high impedance but it is high anyway and was connected directly. It sounded with more bass and treble. When some bass and treble was reduced (from 12 o'clock to about 10 o'clock) it sounded very nice. The sound has some less body than the M55 but this can make it better in a particular song with high pitch male singing. Sometimes more body is produced with male singing at higher notes and this can be compensated with a Pleiades filter of less inductance or for example a less full sounding microphone. The Sony F-96 is a great mic too and sounded well on the Tascam porta 07. The signal output was less than the previous examples. All 3 gain settings has to be at max for full medication. This is due to the fact that it's output impedance is lower than 50KΩ. A low Z Sony F-96 can be tried and a Pleiades transformer with the right Pleiades inductance for bass cutoff designed for this purpose. A 50KΩ secondary would possibly be great.
Later added notes. If the input Z of the Porta 07 is 50KΩ perhaps it is better that the driving impedance be near 10KΩ? More treble? The F-96 hi Z, 10KΩ, sounded fantastic directly connected to Tascam Porta 07. While recording all controls had to be at max. Does the fact it gives a lower signal prevents the op amps to transiently overload? (Transient intermodulation distortion). By playing back through Tascam Porta 02 HS (High Speed) and bypassing the mixer, EQ controls etc (using only the cue function) and listening through Sennheiser HD-580 it is an unheard off brilliant and natural sound. No hiss too. The only hiss that could be heard was coming from the output headphone amplifier. It must also be taken into account that another Sony F-96 sounds very different with much more bass heavy sound. It was tested and compared on the standard Pleiades prepreamp setup. The difference may be the capsules or the design or construction of the internal input transformers. Did They forget to put many laminations no the natural sounding F-96? Or were they inserted in a different way? Or was the mic's specs changed over time so that they may have used less primary turns to compensate heavy bass. The bass heavy mic should sound great on a Pleiades K117 cable prepreamp connected to iPad which has a fairly heavy low cut.
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