Forum Vibe Build help

[igaurav]

I have build the univibe pedal as per the FORUMVIBE schematic (page 8 on http://basicaudio.net/univibe-ForumVibe-final.pdf ).
The pedal is working pretty well except the fact that I am getting too much of mid boost.
Has someone experienced a similar problem... any ideas what could be wrong!!!

LDR/Bulb is from Banzai Music
Power Supply is Regulated 15V DC placed outside the box.

[PRR]

Nothing in the circuit shown would give mid-boost.

My suspicion is a wrong-value resistor or capacitor somewhere. Lots of parts, easy to do.

[igaurav]

Thanks for the reply PRR.
I suspected same thing but I have checked numerous times and all the values are as per the Vintage Build.
I believe the area which can affect the tone is the initial buffer part, Do you have any idea about the caps/resistors in that section...

[R.G.]

I suspected same thing but I have checked numerous times and all the values are as per the Vintage Build.
I believe the area which can affect the tone is the initial buffer part, Do you have any idea about the caps/resistors in that section...

The "vintage build" is pretty much the stock univibe values. The idea is to just make them be the original values. It is worth checking the parts values against another schematic for a univibe to help eliminate clerical errors.

Be sure the orientation of the polarized capacitors is correct, and that the PCB (if that's what you used) or Vero, or perfboard really reflects the circuit you think it does.

How many effects have you built before this one?

[igaurav]

Well... the pcb is etched by myself and have compared schematics also... Caps polarity is also check, I've used tantalums...
Have built almost 15 pedals and a tube amp so far...

[karbomusic]

I built a TriVibe and it doesn't have near enough mids. Maybe we can design your mistake into my TriVibe and vice versa and all will be right with the world. 

[igaurav]

I just now spent a couple of hrs tweaking the input section, by changing input cp, 47K resistor to ground and all... but no luck... finally played with the intensity of bulb and that solved my problem... I believe the bulb was glowing too bright and wasn't going off, after adjusting the trimpots I adjusted so that it shud turn off completely at low speed. Notable fact is that the amplitude of oscillations increase with the speed which affects the tone...
Thanks for extending help guys...