EF95 tube audio preamp
Preamp with EF95 vacuum tubes.
The design is heavily inspired by Electronoobs design. I modified the power supply and adjusted some component values.
The amp is based on EF95 tubes in a Class A configuation (one tube per channel). The gain can be adjusted using two potentiometers.
To reduce noise in the audio signal it is recommended to use a 24V power supply with transformer (no switch-mode power supply).
I created the model using FreeCAD. You can download the files from Thingiverse using this Link: https://www.thingiverse.com/thing:6177183 (or from the section project resources)
You can download all other project files here (including Fritzing-files and FreeCAD+stl files)
measurements and electrical characteristics
- power consumption idle (dominated by the heating current of the tubes): 170 mA @ 24 V -> 4,1 W
- input-resistance: 59 kΩ (@1kHz Sinus)
- output-resistance: 2,9 kΩ (@1kHz Sinus)
frequency and phase response
f = 400 Hz sinus
f = 1 kHz sinus
f = 8 kHz sinus
- main source: https://electronoobs.com/eng_circuitos_tut73.php
- other designs based on EF95-tubes: http://www.hifi-forum.de/viewthread-111-4306.html
- … and https://www.elexs.de/ef954.htm
- EF95 datasheet: https://frank.pocnet.net/sheets/129/e/EF95.pdf
- LT Spice Model LM358: https://www.mikrocontroller.net/topic/184648
- LT Spice Model EF95: https://www.tube-town.de/ttforum/index.php?topic=19590.0