debugging Easy Vibe

[honza]

Hi everybody,
I'am just finishing EasyVibe. I followed the layout from GEOFEX.
Although I can hear some phasing (the rate and the depth controls seems to be working fine),  I have following problems:
- the output is highly distorted,
- it's noisy,
- it clicks when set to a higher depth setting (the frequency of clicks is determined by the rate setting),
- there is a gating effect,
- there is not much difference for vibrato/chorus switch (also not much difference, when the switch is simply disconnected),
- tweaking the drive trim has no audible effect.

I think the LFO works fine. I have also measured the LDR resistances sweep which seems to be reasonable. I have used TL062s and 1n4148s (instead of 1n914s). Does anyone have any suggestions? Please help.

                              Honza

[The Tone God]

Tackle one problem at a time. A big one that stands out to me in your decription is lack of difference between chours and vibrato. There should be a very noticable difference between the two which indicates that somewhere you have a problem with the two signal paths.

Dissconnect the two signals in mixer section. Listen to each one. One should be sound like your guitar clean and the other a strong pitch bending type sound. If you don't get a clean signal then you have a problem with that section. If you get something else with the phase section then you have something funny going on.

Andrew

[jrc4558]

I always check open feedback loops, if anything that was supposed to be clean sound in fact distorted. That's when op-amps are involed, which is the case here. Check the input stage first, then the shifters.

[honza]

Thanks very much for your help.
I checked the whole design again and found a bad soldering in second stage. Now easyvibe works and i must say it's the best fx i have ever made (not really much of them). I have also installed a socket for input cap (33n seems to be better for me, than the original).

I wonder if there exists any simple mod to slightly increase the highest depth setting?

                   Thank you, Honza

[petemoore]

Sometimes the depth will be less, if the LDR's don't do a wide sweep.
 Using some type of vactrol, or LDR's with a 'good' [what the phase stages liek to see] Resistance helps depth.

[honza]

I tried EasyVibe together with RM's Axis Fuzz (guitar->axis->evibe->amp). This combination made the phasing effect much more noticeable. Now I am happy with it.

                                                             Honza