easy vibe sound issues

[fuzzo]

Hi,

I've just made a easyvibe/rotovibe pedal and get some troubles with it. It's basically a standart vibe built with AOPs , photocells and LEDs inspired by some "vibe" pedal (easy vibe , rotovibe , chicken salad) .

I change some things .

The input stage is only a buffer is my circuit ; not a gain stage like the one showed in the easyvibe.

I used 4 LRDs specified for "univibe" sell on "banzai" ;

http://www.banzaimusic.com/Univibe-Photo-Cell-25k-500k.html

I also made another oscillatior I've been working on for few days with a quad AOP . A buffered bias ,  a standart "triangle/square" oscillator built around 2 AOPs (only the triangle ouput is used), then a converter voltage/current with the last AOP with a transistor (like the one is the roger mayer voodoo vibe) .

The vibrato mode works but the chorus doesn't.  I only get the "dry" signal  even if the two resitor are connected to each other to mix them at the output.

Is this a known trouble ? any ideas how I can make this work ?

[R.G.]

any ideas how I can make this work ?

Debugging: what to do when it doesn't work.

[theundeadelvis]

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

[fuzzo]

Hi,

It works actually , like always a mistake on the circuit board . 

I cheked and re-checked and there was missing cut on the tracks of the stripboard  (a jumper in // with the 10K reistor mixing the both signals , that why I only had dry signal on the vibe mode)

Well , for the short time I tested it , it sounds good but a little bit weak in the vibe , maybe transforming the input buffer in gain stage would be a good thing . Vibrato isn't really intersting exept on fast speed.

Although I buffered the bias for the LFO a I still have a cliking noise with the sound, other things to do ? like isolating the V+ between the signal path and the LFO with a R/C filter ? 

[AdamM]

Clicking (or ticking/thumping) sounds are caused by the LFO circuit disrupting the ground/0V for the sound processing circuit.phase shift stages. There are various "fixes" out there including adding small caps across the feedback resistors of the phase shift stages, and adding a 10u cap across the LFO output. However, these are not real fixes, they just mask the effect with varying degrees of success (actually none in my case). I found in my vibe that sorting the grounding out eliminated the ticking completely. I managed this by doing two things - firstly, I moved the 0V connection for the phase shift circuits to be as close to the battery/supply 0V as possible. Secondly, I added a 470u decoupler for the LFO, close to its power pins. Then I routed the LFO op-amp power direct to the 470u decoupler, and from that cap, direct to the battery. This has totally eliminated the clicking, even when the effect is followed by a high gain preamp or overdrive.

[petemoore]

  Try a low current opamp in the LFO position [TL062]. The LFO can get to pulling enough current when passing over a sweep point to put a 'lump' in the audio circuit PS...as you have noticed, it can be enough to be detected in the signal.

[motion2freedom]

I killed clock noise simply by throwing 10uf cap away. can't hear any difference in sound, but the noise is gone. what's that cap supposed to do?

[antonis]

Probably to create clock noise...