￼Application notes for Nutube
Low voltage – Operating from 5V
High quality – Made in Japan
￼Pin assignments & hole sizes
|F1 : Filament 1（Left）||G1 : Grid 1|
|F2 : Filament 2（Center）||G2 : Grid 2|
|F3 : Filament 3（Right）||A1 : Anode 1|
|NP : No Pin||A2 : Anode 2|
|GND : Internal shield, connect to GND|
￼PCB hole arrangements. φ=1.0mm recommended.
￼Basic circuit of Nutube
￼Power supply / Anode load
Audio characteristics on each VCC voltage
on each anode load resistance(VCC=12V)
￼Biasing voltage / resistance
Filament rating:0.7V 17mA(41Ω)
Direct current is recommended.
Inserting capacitor(10μF or more) between filament and GND improves residual noise.
8pin(GND) should be connected to GND to maintain shielding effect.
Recommended resistance values connecting to filament on each VCC voltage.
￼Using both cirucuits
￼DO NOT exceed filament rating (0.7V 17mA).
Excess filament voltage will easily burn out the filament!
A red-heated filament shows excess voltage.
￼To prevent microphonic noise
￼A Nutube is a direct-heating tube which means it can cause microphonic noise.
External vibration reaches the tube mainly through the mounted circuit board and also via the air around the tube.
insert some cushioning(a sponge or something equivalent and soft) between Nutube(or the board mounting Nutube) and the main circuit board. The harness connecting Nutube and the main circuit board should be soft and thin enough.
The vibration of the air (sound) reaching the surface glass of Nutube can cause the microphonic noise especially high frequencies (a metallic sound) .
Placing Nutube in a protective box/case helps prevent such vibrations.
Using acoustic material in the chassis further reduces the noise.
Placing a heavy metal plate (e.g. lead) on the surface of a Nutube can also reduce noise.