The output transformer version 2 of Pleiades V6 is ready

As posted a couple of days ago the primary is 669 turns of 0.1mm diameter enameled wire.


The secondary is 69 turns of orange wirewrap wire. Inductance is approximately 800mH.


The magnetic tape wound core is the Magnetec 079 nanocrystalinne Nanoperm. One can see how tremendous inductance index this core has. With just 69 turns which can be hand wound in less than an hour gives 800mH!


The orange, approximately 3 meters, wire wrap wire filled one layer too. Each turn next to the other. 2 knots are securing the ends in place. The end wires are long and have been twisted as the output is balanced too. The extra length will make possible  connecting to the Neutrick male output socket at the opposite face of the Hammond manufacturing orange octagon box.


So approximately this is a 10:1 transformer. This means it steps down the impedance by 10x10 = 100 times.


Therefore if the impedance of the EF183 electron tube (with the aid of the few megohms anode to grid resistor which increases anode current and therefore trasconductance) is 30KΩ the output transformer would make it 300Ω. This is nice as the little battery powered Pleiades V6 octagon box prepreamp would be able to drive almost anything at almost any cable length.


At least 2 questions arise.


This output impedance should be terminated by something closely low otherwise the responce at low frequencies may drop.


Is this the case too with the Neumann U47? Modern preamps have an impedance of say 20KΩ. Is this a reason helping the Neumann U47 not sounding bass heavy but correct to listener's brain?


References:


(Flat frequency responce from singer's, actor's vocal chords to listener's brain) Sound picture recording and reproducing characteristics - Loye, Morgan - Journal of the motion pictures sound engineers


Pleiades V6 schematic - euroelectron blogspot