Sennheiser MD21 to Pleiades K117 to Pleiades V6 to Sony TC-D5 Pro to Sennheiser HD580

This is an amazing setup.


The MD21 HN sounds super dynamic and quiet while the generously driven EF183 electron tube of the V6 peak limits.


So it sounds loud! The VU meter needles of the Sony TC-D5 Pro can now be near the 0 VU 100% modulation point but the peak indicator LED seldom lights up.


Signal path, setup:


Sennheiser MD21 HN at high Z - Pleiades K117 powered by 1 AA battery - Pleiades V6, connection to grid through the 22nF coupling capacitor in series with what capacitor the gold colored battery electret mic supply adaptor has inside - Pleiades V6 - Sony TC-D5 Pro with its 20db pad at the input to on - Sennheiser HD580


To repeat the signal path:


MD21, high Z - K117 JFET - V6 electron tube - TD-D5 Pro with 20dB pad - HD580


Only perhaps problem a slight reduction of high frequencies possibly due to the MD21 internal transformer for stepping up the impedance


See also Pleiades V5 which is an EF183 driving an EF183.


At the 4 volt operating conditions it seems the K117 JFET has more gain than the EF183 electron tube. So the electron tube is apparently more generously driven.


The needle of the microamp meter connected through the anode circuit is slightly moving to the left at voice peaks indicating electron tube compression.


Perhaps the V6 prototype should include a switchable K117 front end stage? A multi switch could automatically insert a 20dB pad after the V6 output transformer. So instant comparison could be made between the tube generously or not generously driven.


A high Z (direct to grid through capacitor) input chassis socket should be very useful too for connecting an instrument or any other input transformer. Switching the secondary of the V6 input transformer on or off would act as a Pleiades low cut filter. Nice for example for making an electric bass guitar sound not boomy and with great mid and treble detail.


Perhaps also adding another winding of only about 10 turns on the Magnetec 070 nanocrystalinne core for creating an XLR input for the 25 ohm Grampian GR1/L ribbon microphone for use at a few inch with flat frequency response from singer's vocal chords to listener's brain.


References;


Pleiades K177 schematic


Pleiades V6 schematic


Flat frequency response from singer's vocal chords to listener's brain, Sound Picture Recording and Reproducing Characteristics - Loye, morgan - Journal of the society of motion pictures engineers