A schematic can be found by looking for the Pleiades preamplifier on euroelectron.
It uses an EF183 electron tube triode connected, ie anode, suppressor and screen grid connected together ie anode connected to g3 and g2.
The guitar is coupled to the control grid through a coupling capacitor. The value can be chosen for best sound to out ear-brain, depending also on whether we use a bass guitar and how loud. See Fletcher-Munson curves. The value of the capacitor together with the input impedance of the preamplifier which might be 100KΩ adjusts the bass cutoff frequency.
The anode has a 10kΩ load resistor.
3.6V are connected to the other end of this resistor.
3.6V are also connected to the heaters.
A 3.9MΩ resistor is connected from anode to grid to free the electrons.
The signal output is taken from a coupling capacitor connected to the anode.
References:
Operating features of the Audion - Edwin Armstrong
The Pleiades preamplifier - euroelectron blogspot
On preserving transconductance of electron tubes at an anode potential as low as 3.6 volts
No comments:
Post a Comment