Phase Splitters

In a push-pull amp, you need a phase splitter to produce the two identical but in phase opposition signals to drive the power tubes.
Phase splitters are like religions, you belong to one or another and discussions between fans are often emotional.

http://www.bonavolta.ch/hobby/en/audio/split.htm

Love the picture of the red neck lawn mower.

I believe what you are referring to is "Phase shifter" or "Phase inverter".

Wangito.

In my tinkering with guitar amplifiers (I have built a blackface-era Fender Twin FrankenVerb almost from scratch), I learned that a 12at7 vacuum tube is commonly used (at least in blackface era Fender amps) as a phase splitter. The 12at7 is a dual triode (two functional triode sections in one tube).

When the preamp has worked its mojo on the guitar audio signal (a sine wave with alternating positive and negative portions), it presents a voltage-boosted, unified, AC signal (with or without effects) to the 12at7 phase splitter. The full AC signal is fed into identical inputs on each of the 12at7 tube's 2 functional sides--at pins 3 and 8). The output from each half, however, is a split audio signal--i.e., one split being the positive portion and the other split being the negative portion--that is in phase--i.e., kept in sync so that, when reconstituted into a single signal (in the output transformer), the positive and negative portions will once again form a close facsimile of the original sinusoidal audio signal and the output sound will an amplified emulant of the input signal. The way that the signal is split is fairly straightforward. On one side of the 12ax7, the positive portion of the signal is taken while the negative portion is taken from the other side.

The reason for the splitting is so that the power tubes in the amp can be dedicated to amplifying only one of the two phases and, thus, transmit signal at something less than 100% of the time (Class B or Class AB, rather than transmitting 100% of the time as in Class A). That is, half of the power tubes will amplify the positive portion (and maybe some, but not all, of the negative portion) and the other half will amplify the negative portion (and maybe some, but not all, of the positive) portion. By dividing the power amplification effort in this manner, each power tube oscillates between on and off during the portion of the signal and limits saturation in the output transformer which, if allowed to runaway, would make your eardrums explode. In other words, there's a lot more to explain but I have work to do and must stop short,

First, what is a split phase?

It is what is incorrectly referred to as "2 Phase system" Where a single phase current is supplied through a single phase transformer with the secondary winding having a center tape. From each side of the center tape you can draw the same voltage as applied to the primary, and from the complete secondary winding you draw the double. The transformer is referred to as Phase Splitter.

Hope it helps

Wangito

Is this similiar, same, as a dutch double?

Heard the term, not sure if they are the same.

Hi Mr. T

Dutch double as far as I know are a couple living in Holland.

Just kiddin'

Don't know. never heard the term.

Wangito.

Yep, Wangito you're the smartest bloke around, and do not let anyone tell you otherwise either.

The center coupled/tapped secondary winding transformer is probably the most: basic, reliable, and may be the oldest, solution to phase splitting without any serious phase-shit error/s between the two outputs as they really should be exactly 180 degrees out of phase at the same time (right on the dot).

All the other suggestions undoutedly can have cosiderable pase-shift errors between the outputs due to propogation delays caused by all the added components in the cicuit coupled with discrepancies in their values, referred to as Tolerance.

I like your explanations and well said.

The Delta Wye is also a commonly used transformer winding used for Split phase, with Phase to phase voltage being route3 times of the phase to neutral, in a 3-phase system (120degree phase separation) (Commonly 120V Line and 208V Phase). www.Wikipedia.com has a good section on split phase.