Neo-Vibe bulb too bright ?

[axeman010]

Hi there been away from here for far too long!!!

I built a Neo-Vibe a few years ago and it works but I was wondering if it could be a bit more "viby".

I have seen some you tube videos for others builds recently and they sound definitely sound more "viby" than mine.

From the outset I fitted a trim pot to replace R35 and R36 as advised by RG to dial in the sound but its still not right.

Having re-read RG's article and seen some of the videos I know believe that the bulb is not dim enough when the amplitude pot is all the way down. I have tried increasing 47K resistor from the base of the driver transistor to ground to 330K but this has made no difference.


The bulb and LDRs I used are these ones and the LDRs are mounted flat on the PCB

http://www.banzaimusic.com/Bulb-12V-20mA.html

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

I guess my only option now is to increase R48 which is currently 68 ohms.

I wondered whether anybody else has had a similar experience ?

Thanks for taking the time to read this and any help or advice would be greatly appreciated !!!

[R.G.]

I guess my only option now is to increase R48 which is currently 68 ohms.

I wondered whether anybody else has had a similar experience ?

There were (at least) two versions of the original Univibe. One had a pot plus a resistor there, and one had a fixed resistor.

Increase R48 and see how it sounds. Your ear will know.

[axeman010]

Thanks R.G

Problem was the so called 18V DC regulated wall wart I was using !!!! turned out not to be regulated and with no load measured at over 22V.

When I built this pedal some years ago I ran it from two 9V batteries to test it and  it worked well with a lovely thick vibe. I  then substituted the batteries for the 18V wall wart without really paying attention  the effect on the sound.

So working on the premise that an unregulated 18V  was too much to adjust the bulb I tried an unregulated 12V DC supply that I had kicking around and hey presto !!! Bulb now dims nicely and the lovely thick vibe is back. I really must get round to building a dedicated supply for this great unit!!