At your risk. Take safety precautions. Any voltage or current can be dangerous. A fuse must be used in series with any battery for fire hazard protection.
It had been siting on the Pleiades V6 experimental breadboard jig for some months.
Today it was connected to the Fostex M80RP flat coil ribbon figure of eight microphone.
Schematic is the Pleiades V6:
https://www.flickr.com/photos/photoulia/35858046756
Signal path:
Male singing voice at 7in - Fostex M80RP - (optional Pleiades (130Ω,40mH) gentle slope high pass filter - Pleiades V6 with 4722 Peerless Altec input transformer, 2DV4, Rag=2.4MΩ, Vb=1.5V, Pleiades 10:1 output transformer - Sony TCD5 Pro mic in - Sennheiser HD580
Energy is from a AA alkaline battery.
This front end preamplifier takes about half a minute to start operating as heater is deliberately underheated at 1.5V.
The 500μA meter at anode circuit needle barely moves indicating about 1-2μA? But it does move as witnessed with a magnifying glass and amplifier operates like a magnifying device too.
Hiss or thermal noise can be heard as amplifier warms up. If a short circuit is connected between ground and input capacitor hiss almost disappears. If a short circuited XLR (0Ω) is connected to low impedance input (transformer primary through perhaps loose breadboard connection) hiss is reduced but not as much. Both conditions indicate a reasonable low noise performance.
When mic is directly connected to Sony it sounds so bass heavy that sound is unusable.
If a Pleiades (130Ω,40mH) gentle slope low cut filter is connected between mic and Sony preamp the sound is nice with just a bit of bass heaviness left and high bandwidth which may make the sound overall uninteresting.
If the mic is connected to the Pleiades V6 2DV4, no Pleiades filter and then Sony the mic sounds much louder, devoid of bass heaviness. It sounds more interesting without treble heaviness. There is presence.
If a Pleiades filter is included before Pleiades V6 2DV4, mid presence decreases or high frequency emphasis can be heard.
Overall the 2 more interesting or natural sounding versions are the last 2.
It may be attempted to compare performance to the electrometer tube CV2269. Ie connecting the Pleiades V1 concept are Pleiades V6.
It looks almost unbelievable that such an interesting usable natural sound can be created with just an electron tube, 2 signal transformers, one capacitor, one bias resistor, a battery fuse and a battery.
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