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Thursday, 5 July 2012

Cloning the Uni-vibe; Neovibe / Easy Vibe / Phase 45


Legendary guitarists such as Jimi Hendrix, David Gilmour (Pink Floyd) and Robin Trower have made the Uni-Vibe one of the most sought after vintage effects units with originals now so rare that they command huge prices, well into the thousands, even for units which aren't in great working condition. Of the many classic tracks that feature the Uni-Vibe some of the most well known are Breathe by Pink Floyd, Bridge of Sighs by Robin Trower and of course Angel and Machine Gun (among many others) by Jimi Hendrix. Yes, the Uni-Vibe really is the main component in that classic psychedelic, swirling guitar tone and a great effect to play with but if you can't afford to buy an original 'Vibe what are we going to do? Simple; build our own!

If you've never heard a Uni-Vibe (how?) here's a demo video of an original Uni-Vibe in action;


And here's the original inside manual;


Now let's hear it on record. Here's "Breathe" by Pink Floyd, check out the great swirling Uni-Vibe tones throughout this track for an idea of the extra dimensions the 'Vibe can bring to your guitar tone;


Now, lets have a look at a schematic for the Uni-Vibe (Provided by UniVox themselves!);


With an easier to read version;


As we can see it's a 4 stage based phase shift design. Now there are many other 4 stage phaser designs available, the most famous being the MXR Phase 90, but they sound nothing like the Uni-Vibe. Why? Well it's a composite of many reasons:

- It's built using transistor stages instead of opamps with the non-linearity of the transistor stages adding their own magic to the mix.
- Those strangely mis-matched phase shift capacitors which mean that differing amounts of phase shift are applied to different frequencies.
- The fluctuations in the tolerances of the LDRs and lamp rather than matched JFETs that many other more modern phasers use.
- It's strange LFO (Low Frequency Oscillator) design (which itself is known as a "phase shift oscillator") which produces a skewed, non-perfectly symmetrical sine wave which gives the Uni-Vibe that classic "double pulse" sound.

For a real understanding of how the Uni-Vibe "does it's thing" check out this great article by RG of GeoFex; www.geofex.com/Article_Folders/univibe/univtech.htm, it covers everything you need to know!

So, we want to build one. How? There's a few options here. Firstly there is the "Forum Vibe" project which you can find here; http://www.classicamplification.net/forumvibe/, with the information you'll find on the forum vibe pages you'll be able to knock up a Uni-Vibe clone in no time at all. The second option is the "Neo-Vibe" project at GeoFex; http://www.geofex.com/Article_Folders/univibe/vibeupdate.pdf or GeneralGuitarGadgets; http://www.generalguitargadgets.com/pdf/neovibeupdate.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a.

The Neo-Vibe project is an "as close as you can get" replica of the original Uni-Vibe, I've built a few NeoVibes in the past and they do sound great. The "Mods" project on the Forum Vibe site is also great but not a complete replica of the original Uni-Vibe. However, the modifications suggested really do make the circuit *better* (read as "easier to tune in a get sounding right"). The choice is yours!

You may have noticed that the Uni-Vibe isn't the simplest of circuits to build - it's much more intimidating than a Fuzz Face! So what can you do if you're not that confident in taking on such a challenge? Well, you could try the "Easy Vibe". The Easy Vibe is a 'Vibe type circuit designed by John Hollis in which he stripped back the Uni-Vibe to it's skeletal structure and built again with a much simplified structure (it uses opamps....). Have a look over the schematic and compare it with the original Uni-Vibe;


Notice no use of nasty incandescent lamps or dodgy transistors ;-) This circuit is much easier to build and tune in than an original Uni-Vibe and I'd recommend it to those of you who are a little less experienced with the soldering iron. Most importantly - how does the Easy-Vibe sound? Check out this video;


The differences in tone are there, it's just a case of which you prefer.

Again, here's a PCB layout file for the Easy Vibe from GeoFex (RG loves his 'Vibes!); http://www.geofex.com/PCB_layouts/Layouts/easyvibe.pdf

Finally there is one more suggestion I have for you; the MXR Phase 45. By no means am I suggesting that the simple 2 stage MXR Phase 45 can get all the deep complex tones of a Uni-Vibe but it can do something which sounds great and similar in character. For example the "Lovepedal Magicboy Vibe" and many other "small box" 'Vibes are based around the Phase 45 circuit. Here's the schematic for a 'Vibed Phase 45 from JC Maillet where he outlines what each of the modifications does;


For a PCB layout which will allow you to perform these mods go to Tonepad; http://www.tonepad.com/getFile.asp?id=70

A final point that I should make about the Phase 45 circuit is that you'll need to know how to select matched Jfet devices (i.e Jfet devices that turn on at a similar voltage so that the Phaser works correctly). Once again GeoFex has the answer with a full article on jfet matching available here; http://www.geofex.com/article_folders/fetmatch/fetmatch.htm.

4 comments:

  1. Thats for everything you got posted here, youre a true hero, cheers!

    ReplyDelete
  2. You can always buy a Danelectro Vibe and save the trouble of bothering to do anything.

    ReplyDelete
  3. Really nice work, thank a lot for your sharing! btw what are the LDR specs?

    ReplyDelete

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