Valves Tubes Triodes - Ken's Schematics


2011

This page contains electron tube projects T1 was the first listed, T3 the last.  New additions will be made from time to time.

The image below is of an 811A power triode from my collection.  These have been in continuous production since the second world war and even saw service in "Desert Storm".   Handy for RF and audio.   I have a spice model somewhere.  Data sheet   RCA 811A.pdf



T1  Hi Z Guitar or microphone input using 12AX7This is a simple voltage amplifier suitable for microphone or instrument input. The LTSpice file contains the 12AX7 model and should run with the standard library installed.  Capacitance from the plate to ground will kill the high frequency response, try adding some C from the anode to gnd and you will see what I mean.

Try running the FFT (Fast Fourier Transform)

 you will see the harmonic content is much lower than in the single transistor circuit given in project S1, take a larger sample size (many cycles) when running the FFT. Better copyright spice models are available of the 12AX7  on the web than the one used here,  give them a try and compare.

Some good models are available at  http://www.duncanamps.com/

T1_12AX7_preamp.asc     This is the LTSpice file, don't forget to change the font size.

Note: the signal generator V2 in the simulation has a low output impedance this is enhancing the high frequency response, a higher  input z combined with the Miller capacitance inside the tube will reduce the top end response, even fitting a 'grid stopper' will have an effect.


T2  Hi Z Guitar or microphone input using 12AX7 with cathode followerThis is a simple voltage amplifier suitable for microphone or instrument input. The cathode follower has a lower impedance output. The lower output Z would for example be desirable if driving a passive tone control circuit. The LTSpice file contains the 12AX7 model and should run with the standard library installed.
T2_12AX7_tube_preamp_with_cathode_follower.png
T2_12AX7_tube_preamp_with_cathode_follower.asc
T3  Reserved
T4  Fender Champ Model 5F1

Classic fender amp.  Single ended 5 watts output.  The spice models are in the .asc file.  It should download and run. I made a guess at the primary inductance of the output transformer.   If someone could give me the correct inductance,  DC resistance of the windings and  the leakage inductance it would be appreciated.

T4_Fender_Champ_model_5F1_b.asc



I have found a spice model of the 5Y3 rectifier,  it is the same specification as the older type 80 a new octal socket was fitted to create the 5Y3. 

Below is a screen dump of the revised spice simulation.

T4_Fender_Champ_5F1_c.zip

The zip file contains all required to run the simulation with the 5Y3 rectifier. Symbols for all the tubes used are in the folder. Also included are some images and the .asc file.  Run the .asc from within the unzipped folder. The symbols may be added to your library, rename if necessary.

The 5Y3 was actually the older 4 pin type 80 with the newer octal socket fitted. It was old technology when it was first produced in 1935 by RCA (Radio Corporation of America).