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 ?
Quote from: fuzzo on July 27, 2011, 02:36:46 PM
any ideas how I can make this work ?
Debugging: what to do when it doesn't work.
http://www.diystompboxes.com/smfforum/index.php?topic=29816.0
Hi,
It works actually , like always a mistake on the circuit board . :icon_redface: :icon_redface: :icon_redface:
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 ?
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.
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.
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?
Probably to create clock noise... :icon_biggrin: