At your risk.
Take all safety precautions.
Any battery must be connected in series with a suitable fuse for fire hazard or other protection.
The Pleiades V6 1H4 one electron tube preamp with direct heater filament is described on recent posts.
Vf is 1.5V from an alcaline AA Fujitsu battery and Vb is 12V from a tiny Fujicell (garage remote control type) battery. It is still operating greatly from the same batteries.
Altec octal base input and output transformers are currently used.
Attention had been paid to grounding of the transformers so buzz and hum which existed in previous tests is now eliminated to such an extent that when a short circuit is at the input of the Pleiades V6 1H4 preamp one cannot tell whether it is on or off and this by it being connected to the (following) Realistic mic input, (see signal path).
Signal path:
Reverberant room - male or female speaking or singing voice - 635a or SM59 - Pleiades V6 1H4 - Realistic Disco Mixer connected to its unbalanced mic mono in - Sennheiser HD 580 - listener's ear, brain
Excellent smooth sound and very low noise.
635a sounds better on speech than singing, having a bit bass or treble heaviness on signing.
It was used at 3in to 12in.
Vicky observed it sounded much better at an angle of 45o from mouth in the horizontal plane, almost no sibilant problem.
SM59 sounds smooth, detailed without hype and amazing. No sibilant problem.
It was used at 24in to 36in.
The Pleiades V6 running at about 50μA anode current at (low) 12V plate potential at grid space potential is so low noise that a great microphone of low output such as the Shure SM59 can be used at 2-3 ft with no problem.
The taste it leaves is flat fluency response from singer's to listener's brain [Lowe, Morgan] with smooth sound like real life and no noise.
Reference:
Sound Picture Recording and Reproducing Characteristcs - D. P. Lowe, K. F. Morgan - Journal of the Society of Motion Picture Engineers
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