Deluxe 5E3 saturation

Here is a nice Tweed Deluxe 5E3 made by IT-11 Audio (see

This amp is great for blues and rock well known for its early breakup.  What is the first stage involved in this saturate tone ?

Here is the schematic : deluxe_5e3_schem

Here are the voltage (DC and signal AC 1kHz) for the IT-11 Audio Deluxe  :

No doubt that the cathodyne PI is the first to be overdriven :

Yellow trace : « input » : 12AX7 pin 7
Blue trace : « non inverting output » : 12AX7 pin8
« Clean » mode

Higher signal injected :

PI Spiced !

On this SPice model, PI enters saturation with a 40Vpeak signal (28VRMS). On my 5E3, it breaks up when input signal is 22VRMS … Real tube Vs simulation !

Here is the schematic simulated :

… and the non inverting output signal :

By the way : when you use your voltmeter to read the voltage at pin 7 of the 12AX7 PI, you read 17V or something like that : here is what happens (voltmeter impedance) :

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2 Responses to Deluxe 5E3 saturation

  1. Gábor Steve says:

    Hi, what’s the name of the program and which program version did you used to simulate the 12ax7 tube?
    Many thanks for your answer,


  2. t-geek says:

    Hello Gabor,

    If your question is related to PI Spiced part, I use PSPICE. You could also use LTSpice (imho better, but I learnt PSPICE and I’m too lazy to migrate to LTSpice ;-) )

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