Are electron tubes quieter than JFETs?

It has to be re measured.


When we think of a noisy electron tube preamplifier what we hear is not the tubes. It is the power supply 50Hz and harmonics noise, input transformer hum induced noise, possible other component noise etc.


There is not such noise if electron tubes are battery operated.


And there is a further advantage.


The Neumann U47 achieves low noise by operating the VF14 electron tube at low anode and heater potentials.


Why not further reducing these potentials?


This is done on the Pleiades V series pre preamplifiers operating with just 3.6 volts. This is made possible by a 3.9MΩ electron accelerator resistor from anode to grid.


JFETs are fantastic devices. They can operate with just 3 volts too. They do not need a heater voltage.


There must be research on electron tubes that operate wiltout a heater voltage.


Electron tubes possibly have much better gently overload peak limiting characteristics.


The good thing about simple circuits is that active devices like electron tubes, bipolar transistors or JFETs have an inherent flat bandwidth from 0Hz to possibly Megahertz.


For example electron tubes can go flat from 0Hz to Megahertz. They are extremely linear at small signals, and as explained above and in other euroelectron posts, they can be extremely low noise too.


The bandwidth on devices is restricted by the surrounding components. The reactance of capacitors and inductor depend on frequency. Even signal carrying wires close to the chassis by definition form a capacitor. The capacitor by definition tries to keep the voltage constant so the extreme high frequencies are reduced.



Reactance of components varying with frequency can be used to advantage when designing Pleiades filters For flat frequency responce from singer's vocal chords to listener's brain.


General reference:


Electronics - Neil Storey