Easy Vibe build ?'s

[GibsonGM]

Hey all,

I'm really liking these forums! I've learned more in a month checking these posts than in several years of playing around.  Going to put together an Easy Vibe, parts on the way, and have a few ?'s for someone who's done one...

http://www.hollis.co.uk/john/easyvibe.jpg

1)  OK, the TL064's are op amps, so should I power them from a power supply not shown on the Hollis schematic? Most use +9 and -9, so should I just do it that way?  Or do they operate off the 2 LED/1N914 setup on the left of the drawing?   Could I use 2 batteries and go for +/-18v?  If I use a dual supply, the circuit ground would change, wouldn't it?

2) I see in the power section "9v" and "0v"...is the 0v then the circuit ground? If I powered the opamps off of this, I'd have no negative supply - do they not need one for the easy vibe?

3) Since I'm using the TL064...should I use 1 of them for the 4 phasing sections, and use the other for the input buffer, drive/depth/rate stuff? Or does it not matter?  Any isolation problems?  Is lead length critical?

4) I see the 4 LED's between the 'drive' and 'depth' op amps...these are coupled to the LDR's in the filter section, right?  I mean, they gotta be, lol.

Sorry for the noob questions...I want to get this thing right the 1st time!  I've heard the clips, and hats off to Hollis for the design! Someone should draft it up at some point (I will if I get it working).  I've seen the 'debug' drawing, but it's for TL062's....

Thanks for the help!

[d95err]

Opamps require a bipolar supply with reference to *its* ground. To use a single supply, you use a voltage divider to create a positive supply at half the positive voltage (e.g. about+4.5V for a +9V supply). This is usually called Vbias or Vref. Vref is used as the opamp "ground". The opamp then sees +4.5V and -4.5V relative to its ground. In the EasyVibe, one half of the voltage divider is the 10k resistor in the upper right corner, and the other half is made up of the two LEDs and the single 1N914 diode.

The 4 LEDs go to each LDR, yes.

There's a PCB layout around somewhere that uses four dual opamps instead of two quads. It makes the whole layout simpler.

[GibsonGM]

Thanks for the info, d95...I hear ya...so the line running out, that the LDR's ground out to is in fact a virtual ground..cool!  And the op amps are taking V+ from above the 10K resistor, ground between R and diodes, and - supply beneat the led stack. 

I would've used the TL062 schem, but didn't catch it until I'd already ordered the parts, LOL.  I'll figure it out, probably put all the 'tone stuff' on one chip and the 'administrative stuff' on the other.  Doing it on perfboard (I'm brave)...I always use that stuff. Sooner or later, something will get too complicated and I'll give in and buy a kit to make PCB's. 

[GibsonGM]

Just to follow up...feeling really noobish here....the tap off the voltage divider that all the LDR's etc are attached to will be considered 'ground'...op amp power supply comes ABOVE the 10k Resistor at the +9v, and negative op amp supply at the 0 volt, or - terminal of battery?   Sorry, I just haven't used this method of voltage division before!!  I got my awesome Small Bear parts today (great service!!), and don't want to blow anything out....

[GibsonGM]

Wanted to let you guys know that thanks to this forum, I'm vibing away!  BOS     Took about 16 hours total to get the thing togetherin an old Crybaby shell, and a couple of hours of debugging.  Easy Vibe sounds great; I'd like to find some info on getting rid of the light LFO click, and maybe to make the depth greater if I can (using the recommended Small Bear LDR/LED's).   Does anyone have a link to the 'updated' schem. with the resistor changes to ground for greater fidelity?  I've seen it in old posts, but the link no longer works...

One more person who now has the layout of the Easy Vibe burned into their head!! LOL  I don't think I'd want to do it on perf board again, but it was worth it....

[petemoore]

  Tha'ts what I said after the first EZ Vibe I perfed, but, I perfed another...first one works, but doens't follow the schematic, I had to 'circuit bend' a 47k resistor across some OA pins...works.
  The second one is exactly like the schematic, and Vibes beautifully, but sometimes* puts a small 'thump or 'tick' in the Rangemaster...actually I think it's somehow putting tick in the true bypass switch wiring somehow...
  The adjustments for LED Brightness and the other two are a bit hard to 'hear to tell' when maximum sweep depth is attained, I find 'middle of the neck' chording tends to make the depth perception 'surface' a bit more than single notes. I diddle with one knob, leave it set 'somewhere', then diddle with the other knob, Pointer Knobs may be of good service when ferreting out knob settings you like.

[GibsonGM]

Hi Pete,
Yeah, it was interesting...I'm still not 100% sure I got everything right...in the Hollis schem there are 4 1N914's coming off an IC to the bias rail...I put them in opposite polarity pairs like he shows. But the "debug schematic" has them all going the same direction.  I did it according to Hollis.   For more depth I probably have to mess w/the LED's...put the LED's in some shrink tubing, and the LDR's in some larger dia. wire insulation, then pushed them together.  The distance they're apart, and how far in the small tubing the LED's are may matter.   You don't know where I can get a schem of the mod to increase fidelity, at the buffer input opamp, do ya?

I'm trying to get the obvious 'whoosh' of the real thing,  if I can.  A good build, tho!  Good principles to learn for other projects, too.