Twin Reverb tremolo

[Chuck H]

Does it really shift pitch? Seems to me it splits the audio into highs and lows and separately trems them. But I don't see any frequency change.

I think there are some Magnatones that pitch shift. Can't say about the others. I do know that I've heard it in a vintage tube amp. It was pretty awful actually.

[Diablo]

Yeah, the magnatones, old and modern definitely have pitch shifting vibrato. The pitch shift warble is certain in my Magnatone M13.
I have also read that the 5g13 has a phase shift vibrato which shifts pitch.

[Justin Thomas]

As far as the brown/white Fender tremolos go, based on my sample size of having played 3, it is not true vibrato. However, there is some pitch-shift, but it wasn't meant to be the effect. I have read it's more from phasing issues when the hi & low signals are summed before being passed on.

Having played an AC30 with the vibrato & tremolo feature, and just about every kind of tremolo in vintage amps, I prefer the "Harmonic Vibrato of the big brown & white Fenders - the one that uses 2.5 12AX7s.

I thought the Vox vibrato & tremolo were both pretty cheez-whiz, especially without truevariable rate & depth. The Vibro-Champ trem is quite nice; as was that on that old tweed 1x12" I played once. Not sure if it was a Tremolux or Vibrolux. But I think that was mire the particular amo & not the design. I thought the Dwlta Blues did a great helicopter trem, but also lost a ton of volume at higher speed.

Justin

[vintagekiki]

Only Vox AC30 (TB) has both effects on switch selection (vibrato & tremolo)
The difference is noticeable. Vibrato sounds similarly like a phaser.

[Enzo]

Looking at the 1992 schematic for AC30 TB, I see the split phase freq trem, but all I see with the trem/vib switch is a change in the EQ. I don't see how it could pitch-shift. if it can, I'd like to learn.

[glebert]

Some of the Kustom amps had tremolo and vibrato, and they can be run together, but those effects are done via solid state. I know the Defender V100 and the Coupe 72 have this, don't know if others do too. The vibrato is subtle but it does modulate the pitch.

[Enzo]

Surely would like to see a circuit. I see the split freq type where the highs and lows trem at opposite phase, so it fools the ear. But actual pitch change is not simple.

[Diablo]

Here’s how Magnatone does it.
http://www.magnatoneamps.com/FMvibrato.html

[Sea Chief]

best Ive heard is link wray on that song rumble something.. so supro must have done them good. i think he used a supro on that.

[Mick Bailey]

Perhaps I'm missing something with the Magnetone circuit, but it still seems to met to be a phase shift circuit. When I switch my vibe pedal to vibrato and turn up the depth it gives the impression of pitch change, but it's not actually changing pitch. In fact, it gives a pretty good constantly-out-of-tune effect that's the audio equivalent of sea sickness. Is all of this just how our brains interpret phase shift?

If you run a constant sine wave through a magnetone what does the scoped output look like?

[Helmholtz]

Does it really shift pitch?

Up to +/-10Hz acc. to Zollner. AC30 allows switching between pure AM (Trem) and mixed FM/AM (Vib).

[Helmholtz]

but it still seems to met to be a phase shift circuit

A constant phase shift does not change frequency, but varying phase does. Phase modulation means a modulation (expansion and compression) of the time scale which in turn modulates frequency. So phase modulation always means frequency modulation.

[pdf64]

Looking at the 1992 schematic for AC30 TB, I see the split phase freq trem, but all I see with the trem/vib switch is a change in the EQ. I don't see how it could pitch-shift. if it can, I'd like to learn.

Here's a great discussion and explanation of it https://www.guitargear.net.au/discus...?topic=30731.0

Perhaps I'm missing something with the Magnetone circuit, but it still seems to met to be a phase shift circuit. When I switch my vibe pedal to vibrato and turn up the depth it gives the impression of pitch change, but it's not actually changing pitch. In fact, it gives a pretty good constantly-out-of-tune effect that's the audio equivalent of sea sickness. Is all of this just how our brains interpret phase shift?...

According to the dicussion, phase shift and frequency shift are 2 sides of the same coin.

[Helmholtz]

phase shift and frequency shift are 2 sides of the same coin.

Not quite. E.g. the phase shift/lag produced a simple LP filter means a constant time delay for a given frequency. But signal frequency before and after the filter is the same.
It requires a varying phase shift to vary frequency.
In other words, frequency is proportional to d(phi)/dt. (The greek letter phi is the abbreviation for phase. Phase is the argument of the sine/cosine function of the signal.) Means that as long as the rate of change of phase with time doesn't change, frequency will be constant and adding a constant phase shift doesn't change frequency.

[Chuck H]

Just to get back on topic...

Sea Chief, are you going to try a new bug first? If your bugs are old, as in original, it could be worth a try. Lot's of reports about older bugs, uh, buggering the usefulness of the tremolo in that circuit.