Complication of Tremolo Stompboxes

[robbiemcm]

Why are most tremolo stompboxes always so complicated? I mean flashing LED kits seem to work sending the current from one LED to the other. Shouldn't it be as simple as using that same principal and sending the signal from full volume to a second path which could have whatever volume you set it at?

[Paul Perry (Frostwave)]

Why are most tremolo stompboxes always so complicated?

They aren't always complicated (see the EA trem for example) but there are a couple of things that make trems harder than you would think:

1. you don't want any distortion. But, you are using a non-linear device in the control element part...... so there is a difficulty right there, usually.

2. because you want the output 'exactly the same' as the input (except the vol going up & down) any stray noise is painfully obvious (unlike a fuzz). In particular, the LFO oscillator tends to get in & make clicks.

3. The easiest LFO to make is a square or tiriangle. But both have sharp corners, and that means you will get clicking when modulating a voltage control element.

The upshot is, it's easy to make a simple trem if you can live with clicks & noise. But it is suprisingly difficult to make a GOOD one, if what you need is one without noise or distortion, and a LFO shape that sounds "natural'..whatever that is!

[R.G.]

Let me add my voice to Paul's accurate, succinct note.

It is not suprisingly difficult, it is astonishingly and maddeningly difficult to make a good tremolo.

[Tremology]

And...when you finally do make a tremolo pedal, you find that it still sounds nothing like the good old tube amp designs, like a simple VibroChamp circuit.
Tremology

[R.G.]

And...when you finally do make a tremolo pedal, you find that it still sounds nothing like the good old tube amp designs, like a simple VibroChamp circuit.

Ah, but we can give Mother Nature some help. I designed up a Fender-style tremolo circuit replacing the tubes in the oscillator with MOSFETs to drive the neon/LDR bug or generate a bias voltage waveform. Works just like the Fender ones with tubes, has no audio in it, and saves an average of one whole tube for other uses. It's a good trick for tube hackers.

[inverseroom]

OK, Paul and R.G.--what's your favorite simple stompbox trem circuit then?  

[Paul Perry (Frostwave)]

I don't have a favorite. Never in my life have I needed tremolo.
But, the best sounding one, to me, was the purple Dunlop foot pedal one... it seemed to have a chip in it desigened as a volume control with DC control input, to enable people building ghetto blasers & car radios to have the pots away from the main board (obsolete tech now, of course).

If I had to design a simple one, it would be a 555 timer LED flasher, shining on a LDR in the feedback of a simple op amp booster. The LDR should smooth it out a bit & there's plenty of scope to tweak a 555 osc to give various waveforms.

[Tremology]

I know you didn't ask for my opinion, and I apologize if I'm being rude for answering. I have two tremolo pedals that are good but like any pedal, they each have their own "personality".
I like my homebuilt EH Pulsar...the original circuit version. It's crazy and wild but it can get to be raunchy and unmusical. But you can dial it in very nicely, too. I also like my Colorsound Tremolo pedal for its "chop" square wave effect. The only time I use the pedals are for my Princeton Reverb which doesn't have a very deep tremolo circuit.
I would like to see your design, RG. It sounds intriguing.
Tremology

[aaronkessman]

"If I had to design a simple one, it would be a 555 timer LED flasher, shining on a LDR in the feedback of a simple op amp booster. The LDR should smooth it out a bit & there's plenty of scope to tweak a 555 osc to give various waveforms."

thats basically what the Tremulus Lune does. Except the Lune is complicated by the addition of many pots and switches to change the shape of the wave. Stripped down its very very simple. 555 oscillates an LED which is alters the series resistance of an LDR between the two opamps. very versatile, and gets very smooth sounds all the way to the choppiest of choppies.

[Samuel]

There's a 555 in the Tremulus Lune? Looks like it uses something wien-bridge related for the timer circuit (have i got that wrong, or does 555 relate to more than the IC of the same name?)

[R.G.]

I would like to see your design, RG. It sounds intriguing.

No magic there. Just a straightforward redesign to MOSFETs from 12AX7's. I've done some additions that are not in there yet. They're in the (very deep) queue; this includes a PCB layout and an adaptation to bias voltage trems.

It's here, dated 2/05/2002, updated 2/18/2005:
http://geofex.com/Article_Folders/sstremolo/sstremolo.htm

Note that you could use a neon and several LDRs and make this into the controller for a tube based phaser... oops! Did I say that?