Shure Unidyne III reconnected with Pleiades filters, V5, V1 comparison

Now that the phase polarity has been corrected...(wrong cable)...


Here are some Pleiades filter values that sounded the best for the following setups:


Male singing voice - Shure Unidyne III - Pleiades filter - Sony TC-D5 Pro - Sennheiser HD580


No filter bass heavy even at 20in. Problems with low frequency reverberation of room too


With Pleiades 330mH. Less rumble better sound. Mic distance can be approx. 12in


With Pleiadws 160mH. Mic distance can be approx 6in


With Pleiades 53mH thin.


With Pleiades 82mH nice at 1in.


With Pleiades (130Ω,40mH) not sure as the mic has already a rising response.


Then the following setup:


Male singing voice - Shure Unidyne III - Pleiades filter - Pleiades V6, Altec 4722, 7586 Nuvistor, Rag=6MΩ, Cc=22nF, 3.9V - Sony TC-D5 Pro - Senheiser HD580


In general bigger sound, less hiss, more detail.


No Pleiades filter, nice at 12in, less hiss. (The output transformer is doing some low cut).


Pleiades filter 333mH or 100Hz, nice at approx 8in


Pleiades filter 160mH or 200Hz, nice at approx 3in


Pleiades (130Ω,40mH), nice and bandwidth extended


Pleiades 100Hz cascaded with (130Ω,40mH), lower output, leaves something to be desired.


Pleiades 100Hz, perhaps more focused and more midrange than with (130Ω,40mH)


Next experiments will possibly be with Sennheiser MD211 or MD421.


But before this something else had to be retried.


Setup 3:
Male voice singing When I Fall in Love - Sure Unidyne III - Pleiades V1 (160mH military Freed input transformer, CV2269 powered by one AAA battery, resistance capacitance coupled to a Canford transformer inside a 1/4in jack - Sony TC-D5 Pro - Sennheiser HD580


The best sound so far from Uni III. At a distance of 1in. No gain but a nice smooth sound. Going back to setup 1 with 160mH, the sound was more mid oriented and less clear. Going back to setup 2 with a 140mH Pleiadss input transformer the sound was more mid pesky and less clear but of high gain. The pad on the Sony then was switched on. The CV2269 electrometer Pleiades V1 electron tube circuit although with some more hiss sent in this application for tea the rest.


http://euroelectron.blogspot.com/2015/10/pleiades-electra-13v-electron-tube-pre.html


http://euroelectron.blogspot.com/2017/08/description-of-pleiades-v1-electron.html


Later addition: The Sennheiser MD441 U3 was connected. It sounded very nice with just a Pleiades (130Ω,40mH) directly to Sony TC-D5. It sounded very nice to setup 3 ie Pleiades V1 with a full sound, silk smooth and less HF possibly compensating Fletcher Munson, voice effort curves for flat frequency response to listener's brain. Setup 2 ie Pleiades V6 sounded very nice with the Pleiades (130Ω,40mH) to Altec 4722 (but not to Pleiades 140mH input transformer, lack of bass due to low input inductance) with much more treble and much more gain.


So again the Pleiadss V1 with just an AAA battery sounds great with no need to do anything else. (No Pleiades filter needed just the 140mH inductance of the Freed military transformer which in fact is reduced with increasing frequency!). The rest of the circuit is also doing processing. Bass and treble cut from perception compensation must be done by the high internal anode resistance of the electron tube operating with Pleiades bias and only 1.2V including both heaters and the anode circuit. In fact the anode is less as there is the little load resistor voltage drop. Perhaps the circuit is also processing peaks as the anode supply rail is ridiculously low.


Interesting. Again proving what Jim Morisson said. We are trying for something that has already found us.


The Pleiades V6 is of course more treble detailed. And the Nuvistor 2DV4 or 7586 can be tried with just 1.2V at the anode. The fact that V1 is not treble detailed gives it a fuller sound with balance compared to the low end of the spectrum. Possibly the Olson experiments demonstrating that missing low octaves should be accompanied with missing high ones? On voice 20Hz to 100Hz is missing anyway? Or the reason is Fletcher Munson, voice effort compensation. It is funny that sometimes when you know less, go with instinct and make mistakes you can do more. It is possibly the defects of the Pleides V1 that make it sound quite correct to listener's brain.


Further reading: Flat frequency response from producer's brain to listener's brain. Sound picture recording and reproducing characteristics - D. P. Lowe, K. F. Morgan - JSMPE