555 based tremolo

[lerxst88]

hey i was playing around with a 555 timer and an LDR and i came up with this simple to build, great sounding tremolo.

2 problems: volume is significantly lower than unity gain and sometimes there is a little click when the LED is blinking. help?? thanks!!!

heres a schematic i drew up:



sorry i forgot to label the IC! pin 1 is GND and pins 2 and 6 are connected (might be hard to see)

[svstee]

Looks interesting, I wish I knew more about 555 chips. You don't have any gain recovery or boost, so it makes sense that your volume is less than unity. I might try it in a couple days and see what I can do.

[lerxst88]

the 555 is basically a timer that according to the resistors connected to pins 8,7, and 6 will send out a pulse at a certain frequency. the capacitor value will put the frequencies in a certain "range" bigger values will have longer pauses between pulses. 2 and 6 should just be connected.

i was also thinking about putting a transistor or an op amp right before the output to boost the signal but it might distort the signal.

yes please do give this a quick build! the results sound pretty sweet albeit a bit too quiet for practical use. i worked on some vintage fenders over spring break and i saw that their vibrato circuitry used an LDR

[jacobyjd]

this is kind of an interesting approach--The first thing I would try (with my limited knowledge) would be to add an input and output buffer before and after the switch pins, with the 555 circuit in between. The output buffer could also double as a gain recovery stage if it's a little too quiet

[MikeH]

this is kind of an interesting approach--The first thing I would try (with my limited knowledge) would be to add an input and output buffer before and after the switch pins, with the 555 circuit in between. The output buffer could also double as a gain recovery stage if it's a little too quiet

Basically you'd end up with a tremulus lune kind of thing, but with a 555 controling the opto, instead of all that 4558 LFO mumbo jumbo. 

[lerxst88]

So how could i build an output and input buffer?

[Derringer]

http://www.muzique.com/lab/buffers.htm

[smallbearelec]

So how could i build an output and input buffer?

What you wind up with is either the Tremulus Lune that someone mentioned, or my Tremulous Bear:

http://www.smallbearelec.com/Projects/TremBear/TremBear.html

Your basic idea is interesting and can probably be made to work. However, 555-type trems are notoriously subject to "ticking" resulting from the switching of the internal op-amps dumping noise onto the power supply rails. The problem gets worse when you add the gain stages. Pay major attention to layout, and follow R. G. Keen's rule: Ground oscillator and modulator sparately, and join grounds only where the negative supply lead enters the board. Other tips are in my article.

Regards
SD

[lerxst88]

So here is my revised circuit (basically with a buffer)

thanks again for all the replies and help! i love learning about this stuff! also its an honor to have small bear electronics reply!

anyway i put in a buffer and wow the 555 clicks like a mofo! its really loud and now instead of a tremolo its more of a noise generator haha. im thinking i should put another buffer on the output somewhere??

thanks agaiin to all who replied!!

[CynicalMan]

Try adding a resistor in series with the output of the buffer before it reaches the circuit output and the photoresistor. Then, the photoresistor and the resistor will act like a voltage divider varying the amount of signal going out depending on the 555's waveform. The guitar pickups' series resistance was probably doing this before.

[brett]

Hi
I'm no expert, but here's my 2c....

Try placing a large cap in parallel with the LED so that it brightens and darkens steadily rather than switches sharply.  Alternatively, you might consider driving the LED off pin 2 (using an emitter follower or similar), because it is part of the timer system that charges and discharges.

RE: 555-type trems are notoriously subject to "ticking"

1. There's no smoothing capacitor on the power supply, maximising you chances of noise.  22uF and a 0.1uF in parallel would help a lot.
2. Try a CMOS 555 (TLC555).  They are much quieter.


cheers

[rousejeremy]

Has anyone made any more progress with this?

[soggybag]

I have often wondered how to deal with ticking generated by the 555. I remember reading a suggestion to use this arrangement.

Place a 100uf cap with + to Vcc and the other connection to pin 1. Between pin 1 and ground place a 1n4001 diode.

[earthtonesaudio]

The CMOS 555 uses less current and produces MUCH smaller spikes (because it uses less current).  Use a cap with low ESR  for bypassing, and you can get away with a smaller value. 

[ds-2isthebest]

What if i remove the LED and photo resistor? will it still work?

[duck_arse]

ds-2, the ldr/led combo is what makes the tremolo in this effect. removing them means you will have a buffer.

the circuit just above needs a dc blocking cap between the output of the opamp and the bypass switch.

if you want to prevent ticking, build the 555 on a seperate pcb from the audio section. run separate V+ and ground from the 2 boards back to the battery. and include the resistor and cap supply filter on both boards.