After playing with it for about a month or so in the stidio and live I decided to modify some stages, namely input.
There we have a 47k-100k negative feedback network in the first op-amp, that takes the signal from the input 0.001mF capacitor. I replaced it with a 22mF/470ohm (to ground) combo and a 1kB potentiometer in the feedback loop. The fidelity of the signal improved dramatically and now the volume can be controlled with a knob. The tone is smoother and warmer.
I haven't met too many people using "Vibrato" function of the Univibe clones, so the switch is gone and the thing is hard-wired for Phaser.
The speed potentiometer was changer to LogA and is now wired backwards. Way better sensitivity.
Hope someone will find this useful. Peace.
hmmmmm... i was thinking of building an easyvibe, and these mods are pretty tempting. one thing i was thinking, is the classic univibe, using the bulb and things, had that AWESOME uneven sweep. is there any way to do that on purpose?
cheers
Jim
I guess the LFO on EazyVibe is already altered to produce this kind of shift. The capacitor values (from 470pf to .22mf) in the filter stages also contribute to "bouncing" phase shift.
oh excellent. is there any way to modify other pedals, like the small clone perhaps, to do this?
cheers
Jim
Hi Jimmy
I've see on the web a schematic for the lamp version of the Easy vibe but i've lost the link,hum i'm going to search him
More there's a way to do a real Univibe clone,contact me i will give you the links.I've done three Univibe clone ,one of them is in my main rack,instant Breathe Pink Floyd Phasing sound!!
Bruno
Hi ,
Here's the link for the modified easyvibe
http://www.geocities.com/stompboxworktop/easyvibe.html
Regards
a few questions about this
There we have a 47k-100k negative feedback network in the first op-amp, that takes the signal from the input 0.001mF capacitor. I replaced it with a 22mF/470ohm (to ground) combo and a 1kB potentiometer in the feedback loop.
the 22mf/470ohm to ground, they're in series right?
the 1k pot wasnt enough for my circuit, it needed about 2k to get unity gain and good sweep, so i put in a 5k trim pot and dialed up till it wasnt clipping the sound.
any one else trryed these mods?
Also I brought one of the tri colour leds, and have wired it in to the chours/vibrato switch (DPDT) now i have a green light for chours and a red one for vibrato. cool huh. 8)
Quote from: Hungeryhippie
any one else trryed these mods?
I was thinking about doing this to mine. Did it improve your sound also?
i think it did but i spent the week end working on and off on it at first it sounded terible and that was cos i didnt put the 470/22mf to ground i put it to the vr, woops, now its to ground and it works.
but it tock me so long to do it i forget how it sounded before :shock:
but in general it sounds good. brighter i would say if any thing,
If I understand electronics right, the gain is defined by proportion btw fedback resistor and to ground resistor. HOWEVER.
If you will start changing values of the resistors going to ground you have a good chance of affecting trebles. Try it in a TubeScreamer (take say 2.2k instead of 4.7k and a larger capacitor) and you will know what I'm talkin about. :idea:
The same thing happens here. We're just allowing more signal in and through the cirquit. And more treble content too. I like mine this way much better. 8)
Regarding the ground-Vref and where to connect the capacitor to: Normally this is irrelevant in the pedal world.