Here is a nice Tweed Deluxe 5E3 made by IT-11 Audio (see http://www.it11audio.com/deluxe).
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 :
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 :
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) :