Making This Tremolo Guitar Sound

[Duncster94]

I'm sure it's probably just an LFO automating the volume, but in case it's something else I thought I'd ask here.

You can hear it very clearly at 0:44 and several times after that.

https://www.youtube.com/watch?v=Zy5Uyo-gaEo

Thanks in advance!

[aciddose]

This is a standard guitar tremolo pedal effect.

They usually work by modulating a FET to adjust the resistance to ground at the input of a buffer in most cases. Only rarely do they use an LDR which has a far more linear sound.

In both cases the LFO shape is not a perfect sine, as well as the response of the volume to the modulation is non-linear.

In the case of the FET, the result is a very "square" on/off pulsed timbre as the modulation crosses the gate threshold voltage of the FET. Beyond this voltage the resistance very rapidly becomes either almost infinite or nearly zero (typically 100 megs vs. 10 ohms.)

In this example it sounds more like a LDR based effect. This is slightly exponential and so you get low rounded valleys with sharp peaks between.

Both of these waveforms are trivial to duplicate in software and many good tremolo effects exist.

Depth seems about 50% in this particular case.

[Duncster94]

Hey, thanks for the in-depth explanation!

While we're on the topic, what kind of distortion do you think was used in addition to the tremolo? Is it just a simple overdrive? I bought my friend's electric guitar a few weeks ago and I've been looking into different types of distortion effects but I'm never 100% sure that I'm identifying correctly what I'm hearing.

Thanks

[aciddose]

I'm not certain. Distortions have many different factors such as pre-EQ, waveshaper, post-EQ and so on. Not really my specialty and definitely not when used to process guitars.

I could only guess and so I'd rather not.


...although it is important to note that the cheaper tremolos using a BJT rather than a FET will likely have very significant distortion themselves. The signal passes far more when positive than negative in such a circuit. The better quality tremolos use FETs which act as variable resistors, but a BJT based effect is more like a variable diode.

That sort of distortion is minimal while the LFO is not reducing the volume and maximal while it is reduced as far as possible. In many cases such a circuit can't modulate all the way to zero, generally getting 50% depth at best.

The circuits are extremely variable. Software is not so variable as it is trivial to produce zero distortion and non-trivial to model the cheaper tremolo circuits.