Frequency doubler phase

[Danich_ivanov]

Here's the circuit. The pedal i'm working on right now has a similar circuit within, and i'm trying to figure out as to whether or not it reverses the phase, and what does it do to the phase at all, as there are two out of phase signals collided together through this (what I would call) a "differential amplifier" type construction. Please educate me on this.


Thanks.

[anotherjim]

You'll get the classic full wave rectified signal out of that.

T1 is a phase splitter or concertina. The collector has an inverted output while the emitter is in phase with the input. Both outputs should be about x1 gain. Trimmer P1 is there to help balance the amplitudes of the 2 outputs. The best "frequency doubled" sound is when the output levels are matched, although that only happens with a properly symmetrical input signal in the first place, which guitar seldom is.

Each phase drives an emitter follower amplifier T2 or T3 within which they are mixed together by the common emitter resistor R9. T2 & T3 will both have unity gain and trimmer P2 is there to get T3 DC level to match that of T2.

With both trimmers set properly, the output at R9 could look like this...

[PRR]

> trying to figure out as to whether or not it reverses the phase

Why do you care?

As Jim shows, half the time is in-phase and half time is out-phase.

Why could you care about phase in guitar work?

The usual reason is because you are mixing two copies of the signal. If one path has an extra inversion, but is otherwise identical in gain, you get nothing. More often the two paths have different gain (especially frequency response) and you get a hollow weak sound.

But mixing a full wave rectified back to the original....at equal peak levels (which is not practical) you get some form of buzz/fuzz still having the pitch-sense of the original-- you lose the point of the doubler. I guess it degenerates to a half-wave rectifier.

[Danich_ivanov]

You'll get the classic full wave rectified signal out of that.

T1 is a phase splitter or concertina. The collector has an inverted output while the emitter is in phase with the input. Both outputs should be about x1 gain. Trimmer P1 is there to help balance the amplitudes of the 2 outputs. The best "frequency doubled" sound is when the output levels are matched, although that only happens with a properly symmetrical input signal in the first place, which guitar seldom is.

Each phase drives an emitter follower amplifier T2 or T3 within which they are mixed together by the common emitter resistor R9. T2 & T3 will both have unity gain and trimmer P2 is there to get T3 DC level to match that of T2.

With both trimmers set properly, the output at R9 could look like this...

Alright! When you said full wave rectifier and shown the graph it all came together, thanks.