Neovibe gripe

[Chris Goodson]

I think the Neovibe is a cool pedal but one thing that annoys me is the more I cut the depth pot back the thinner the sound gets.  When I set it to the amount of mix I'd like to use I no longer like the tone I'm getting.  Is this normal for these?  Is there a remedy?

[R.G.]

"depth" on that pedal, just like the Univibe it's a clone of, only changes the amount of modulation of the light on the LDRs, leaving the LDRs more at a single place in the sweep. It doesn't really change anything else, so I'd guess that you don't like where the cancellation notches happen to be sitting when the depth is turned down.

There are some possibilities. You could try adjusting the bias/idle current of the lamp. That would leave the notches sitting at a different frequency. You could try leaving it at full depth all the time and instead of modifying the lamp modulation, change the mix at the output, which has the effect of reducing the depth of the notches.

As to whether it's normal, you may have to hunt down the Japanese engineer that designed the Univibe - the NeoVibe is a faithful copy of the audio path and the LFO.

[dr]

.....I got a lot happier with the sound of my Neovibe when I made the leads of the ldr's longer and experimented with various angles away from and closer to the light source....and I ended up using those ldr's from those automatic "night lights"not any fancy ldr's....also,that 500 ohm bulb trimmer became a panel mounted pot (as did the 200K pot instead of the pair of 100k resistors).....THANKS SO MUCH,R.G.!!!!!!!!!

[keninverse]

which 100K resistors are you talking about?

[R.G.]

The "chorus" output is a 1:1 mix of dry and phase delayed signal through two 100K resistors. The two resistors are just before the chorus/vibrato switch at the output.

For deep phasing sound, the dry and wet signals must cancel to within at least 20db - another way of saying that is that the dry and wet signals must be within 10% of each other at the notch frequency. That means that no accumulated tolerances of signal amplitude can mismatch the dry and wet amplitude more than 10% if you want good phasing.

The 100K resistors themselves have a 5% tolerance. If one is high, the other low, there's your 10% on the spot. That would be rare. But it's easy to lose 5% on the resistors and another 5% in the non-perfect gains of the transistor phase stages.

The secret to making even vintage univibes sound ...great... is often to diddle the mix resistors. A good way to do this is with 82K resistors and a 50K pot, the mix being taken off the center of the pot. You can tweak in a mismatch of up to about 20% that way.

Try it - you'll like it.

[dr]

....the resistors that I subbed a pot for were R35 and R36 that form the wet/dry mixof the signal.It is mentioned at JD's site (General Guitar Gadgets) in the Neovibe file (PDF)....this mod alone as well as playing around with various angles of the LDR's around the light source;mounting the bulb bias pot on the panel instead of an internal trimmer made a HUGE difference in the flexibility of the sound.....I even experimented with different reflective and non-reflective light shields of various sizes and shapes before I set my version in stone.....

[LyleCaldwell]

The secret to making even vintage univibes sound ...great... is often to diddle the mix resistors. A good way to do this is with 82K resistors and a 50K pot, the mix being taken off the center of the pot. You can tweak in a mismatch of up to about 20% that way.

Try it - you'll like it.

R.G.,

Looking at the two 100K resistors on the PCB, do you suggest running wires from the left solder pad of each resistor on the PCB to one side of each resistor, and the other side of the resistor soldered to the outer lugs of the pot, with the wiper wired to one of the right solder pads on the PCB?

[newperson]

I used a 200K trim pot for the 2(100K) resistors.  The middle pin of the trim pot goes to the "N" pad and the other legs (1 and 3) go into the other other ends of R35 and R36.  So looking at the PDF layout, the trimmer legs 1 and 3 into the left side of R35 and R36 holes and the middle 2 pin goes into the "N" pad on the board.  This worked fine for me.

Paul.

[no one ever]

While we're on the subject of Neovibes and R.G.

What's pad P for?

[LyleCaldwell]

Paul,
That makes sense, thanks.