Method of switching a microphone front end preamplifier without transients

Summary:


By continuously applying anode voltage and switching on the heater circuit of electron tubes.


Description:


This eliminates the step function switching transients to the following stages.


Anode voltage is applied continuously. There is no power consumption as the cold cathode does not emit electrons. Therefore no anode current flows.


The heater voltage is only supplied by the on off switch.


The anode current increases gradually, comes gradually to life, as electron emission begins whiout switching on transients. Sound just slowly fades in.


The same happens for switching off. The sound gradually fades out.


This method should pose no risk especially to electron tubes operating with a low anode voltage. It is used on the Pleiades V6 pre preamplifier operating with 3.9V.


The silent, gradual on off function reminds switching on electron tube condencer microphones such as Neuman U47, AKG C12A, AKG C24 etc. The U47, and C12A are deliberately with lower heater voltage and this makes the fade in even more slow and enjoyable. Same for the Pleiades where the heaters are supplied with less heater voltage too. Even when underheated, the Pleiades V6 gain may be observed to increase after switching off the heater for a while. Is this an electron tube or output transforer effect? See nearby in time euroelectron posts.



The Pleiades V6 front end is usually used with moving coil or ribbon microphones. It can be connected to any other type.


Conclusion:


All other equipment can be at their normal gain setting, when the prepreamp is switched on by switching the heaters on. The sound very gradually fades in. Or fades out after switching the heaters off.


Reference:


Pleiades V6 schematic