can someone give me a phase inverter tutorial

[wsaraceni]

so i was looking at other amps topology. how does the 5e3 deluxe work out. is that a totally different phase inverter type?

does this work by the first half of the tube setting the phase that goes to the poweramp through the two resistors and the other half goes through the 2nd triode and flips phase there?

[rock_mumbles]

so i was looking at other amps topology. how does the 5e3 deluxe work out. is that a totally different phase inverter type?

Yes, it's called a cathodyne or concertina PI ... totally different setup, character, etc. they are also found in the Princeton, in most Orange amps, and recently in the Peavey Windsor.

While you are at it you might as well look at a 5D3 with its paraphase inverter, there's also a slightly different version called a floating paraphase.

The Valve Wizard site discusses these (at an intermediate electronics level)
LTPI
http://www.freewebs.com/valvewizard/acltp.html
cathodyne
http://www.freewebs.com/valvewizard/cathodyne.html
paraphase
http://www.freewebs.com/valvewizard/paraphase.html
floating paraphase
http://www.freewebs.com/valvewizard/flo ... phase.html

[jjman]

so i was looking at other amps topology. how does the 5e3 deluxe work out. is that a totally different phase inverter type?

does this work by the first half of the tube setting the phase that goes to the poweramp through the two resistors and the other half goes through the 2nd triode and flips phase there?

The 12ax7 in a 5E3 has a gain stage and a PI stage. There is no second triode in the PI. Rather, the PI has a bottom (cathode) tap and a top (plate) tap.

[tubeswell]

The cathodyne
Inverts the signal by having 1/2 the triode working as a conventional 'inverting' stage, and the other half the triode working as a cathode follower stage.

In an inverting stage, as the grid voltage swings more +ve, the tube current increases and there is more voltage dropped across the plate resistor - so the plate voltage drops. (Think Ohm's law: Voltage = Current x Resistance)

Meanwhile at the cathode, the same increase in tube current that has cause the plate voltage to drop, causes the cathode voltage to rise, because there is also more voltage being dropped across the cathode resistor (because there is more current flowing through it). So the cathode voltage goes up when the plate voltage goes down, and vice versa when the tube current decreases. That's how the signal gets inverted.

There is no gain from the cathodyne per se. A properly-balanced cathodyne (where the plate and cathode resistances are the same) has 'unity gain'. (But where you use a dual triode as a pair of driver/cathodyne PI stages, you get gain from the driver stage).

Seeing as how a cathodyne in a circuit like a 5E3 or AA1164 is cathode biased and as an almost infinitely high input impedance, the maximum mount of clean output swing from a cathodyne is limited by the load (combined value of plate and cathode resistors), and the impedance bridging to the output stage. If you have a higher HT voltage supplying the cathodyne, you'll be able to get more clean swing.

The LTP
Inverts the signal by having one side (the input side) functioning as a conventional inverting gain stage, whilst the other side is driven by the changes in cathode voltage (with the grid tied to ground at AC) and is non-inverting.

As the grid signal in the inverting stage swings positive, the tube current of that stage rises and the voltage at the plate falls (because of the effect of increased tube current flowing through the plate resistor). At the same time, the cathode voltage rises because the voltage flowing through the tail resistor rises (because of the increased current).

Now because the cathodes of both stages in the LTP are tied together, and at the same time as the cathode voltage rises in the inverting stage, it rises in the non-inverting stage. But when the cathode voltage rises in the non-inverting stage, it has the effect that the tube current in that stage is decreased (because tube current in that stage is not being driven by that stage's grid, but by the cathode) so the plate voltage in that stage rises.

Either output of a LTP has a gain of about 1/2 of what either triode would have as a conventional inverting stage with the same load. But you can get a bigger clean signal swing out of each plate of a LTP than you can out of each output of a cathodyne at the same HT voltage.