Need Help with Easy Vibe!!!

[GibsonGM]

Hi, Building the Easy Vibe tonight....I see the voltage divider, top is V+, the tap above the 1N914 would be ground, or 0V, and at the bottom should be V-, for powering the Op Amps, correct?  I'm confused how the bottom is labeled "0V"...does that mean the "0V" point over by the output is actually connected to V-?   I'd think that would be ground (where the 1n914 tap is...)   The rest of the assembly seems fine, I'm just questioning that!  Thanks for the help, I'm dying to finish this thing!! 

[Dan N]

I built mine from the geofex.com layout. Zero is good old fashioned ground.

[d95err]

It seems like you are confused on how to use opamps without a bipolar supply. There is no negative voltage in this one. Just connect the positive battery pole to +9V on the circuit, and the negative battery pole (ground, 0V) to 0V on the circuit. On the opamps, 9V goes to Vcc+ and 0V goes to Vcc-.

The signal is biased around the voltage created by the voltage divider, about +4V. The opamp doesn't care about the absolute values of the positive and negative supply. It only cares about the relation of its V+ and V- compared to the DC voltage on the inputs. Since the DC voltage on the inputs is +4V, the +9V supply will look like +5V, and ground (0V) will look like -4V from the opamps point of view.

[GibsonGM]

Thanks a bunch, 95.  Thought that was how it should be - it makes sense!  Just didn't want to fry anything.  Yeah, I'm used to using 2 batts, or tapping a 9v into +/- 4.5.   I'm going to look into op amp biasing, it looks pretty handy.  So that bias rail is setting an approx. midpoint for them to operate around....hopefully this will work, should be all done in a day or so! 

[d95err]

The EasyVibe is rather unusual in the bias design. Most opamp 9V circuits use a resistor voltage divider to get a +4.5V bias supply. The EasyVibe uses that strange resistor/diode arrangement to get an asymmetric bias supply. Don't know why, and some people suggested on this forum that converting to a regular 4.5V bias will help reduce ticking and improve the sound. I tried that on my build, but I couldn't hear much difference.

[GibsonGM]

That's what threw me, 95.  I read something like 7.5V across the battery, and 4.something at the bias rail...it was greater than half, I thought that was off.  I'm thinking the TL064's may be sensitive (JFET), so I want to make sure the supplies are ok before I plug them in.   Doing the optocouplers & power hookups  tonight; hope it works!  From the samples I've heard, it sounds like a nice alternative to dumping all the $$ on a real Univibe.   Now that I've been all over the schem, troubleshooting will probably be easier, ha ha! Mine will probably click, I have long jumpers (using a perfboard, arrgh).   That's what modding is for, right?