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Re: The Technology of the Univibe


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2/3/1998 3:10 PM
R.G. Re: The Technology of the Univibe
>there isn't *any* bypassing on the output side of >the 7815. Shouldn't there be at least a .1uF??  
 
Dang! You're right. I'll have to mod the board, at least to provide the instructions to hack one on.  
Thanks.  
 
>My understanding is that the Univibe was  
>originally intended to be a 'vibrato/chorus' and  
>not a phase shifter as we know them today. The  
>purpose of the Univibe's phase shifter is to  
>advance and retard the phase to increase and  
>decrease the pitch of the sound. Basically the  
>same way doppler shift works.  
 
Another one! That IS a cogent basis for why the phase shifts are distributed. It would make for a better-spread vibrato.  
 
The nulls don't really come into it until the dry signal is mixed with the delayed signal to cause the nulls. However, the distributed phase shift to keep the whole spectrum moving with respect to TIME is a great observation.  
 
I did two other variations on intensification.  
(a) add feedback around the phase stage  
(b) Use the PCB program's macro provisions to make  
an Ultravibe with eight phase stages. Mark Amundson built the proto on that one, worked first shot - which I attribute to Mark's skill.
 
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2/3/1998 3:56 PM
John Greene
The nulls don't really come into it until the dry signal is mixed with the delayed signal to cause the nulls. However, the distributed phase shift to keep the whole spectrum moving with respect to TIME is a great observation.  
 
Yes, they do need to be mixed. However, my point was that the .47uF cap causes the chain to start off with some amount of shift. This puts the first point at which there is a 180 degree shift (all stages contributing) at around 100Hz. When mixed with the dry signal this is where there is a null. The phase slope is constant at 180 degrees/decade which means there isn't another null until 10KHz when the wet and dry signals are mixed. The shifter moves this sloped line back and forth WRT frequency causing an even shift in phase across the range of use. The Nulls (when used as a chorus) were intended to fall as far above and below the range of the guitar such they wouldn't effect the sound very much. When I plotted the phase shift through the network I was pretty surprised on just how constant the slope was. Pretty cool design.  
 
--johng
 
2/4/1998 8:58 AM
anonymous
(Re : adding .1uF bypass to "output side of the 7815")  
 
Where?  
 
Why?  
 
-j
 
2/3/1998 3:09 PM
Greg
Could one of you guys take a look at this site:  
http://www.lynx.bc.ca/~jc/ under Music Pedals DIY. There's a brief bit about a 1968 Shin-Ei Univibe and some different cap values. I'm curious of any thoughts. Thanks.
 
2/3/1998 4:17 PM
R.G.
Been there. I've corresponded with J.C. on this several times. He readily says that the choice of capacitors is because of a decade relationship between two of the caps, plus some other considerations, all based on the phasing.  
 
I've never been able to understand his reasoning based solely on the phase shifting aspects of the device. Maybe this whole issue is a failure on my part, a kind of technical blind spot. It's very frustrating, as I usually can eventually dope out what is happening in a given effect and why.  
 
Even taking JC's notes into account, John's explanation about spacing the phase capacitors in a way that makes the vibrato work better in a dual mode device is the best theory I've heard (mine included!)  
 
I have one of JC's books on the way, I should know in a few days about the technical content in there.  
 
There is some more history on the Univibe and it's predecessors (!) from Shin-Ei in a new book entitled "Stompbox" that I picked up a couple of days ago. No technical details but some good history and perspective.
 
2/15/1998 7:55 AM
JD Sleep

RG,  
I'm not sure if this is an appropriate forum for a book review, but would it be possible to let us know what you think of JC's book after you have looked it over? I thought the effects book on his web site looked interesting, I wondered what you (or anyone else that has it) thought of it.
 
2/15/1998 9:30 AM
R.G.
I don't know about a book review, but I have a copy that I received on a trade. I was hoping to gather up info on effects that I haven't seen before - I'm always looking for more information and understanding.  
 
In terms of content, "Rainbow of Sound" contains three major sections, a compendium of schematics, some info on making and debugging effects, and almost 50 pages of photocopies of data book pages.  
It's a self-published book, soft covers and plastic-finger bound.  
 
The compendium of schematics contains 57 different effects. Of those, 20 are schematics that I personally drew up and 17 were drawn by Jamie Heilman, all 37 of which were placed on the net in Jamie's Musical Micro-Archive/Leper's Schematics, and are still available if you want to unpack the .zip file and print them; there are many others in there too. I was a little surprised to see that work reproduced in a for-fee book.  
 
Of the rest, 14 were photocopies of either magazine articles of effects projects (primarily Anderton in GP) or a copy of the service/reference literature from an effects maker. One was a print of the voltage controlled panner from Forrest Cook's web site, repro'ed with copyright notices and all.  
 
The author drew up unique originals of 7 effects (although there were some drawings that duplicated other effects as well). These 7 are:  
Armstrong Orange Squeezer  
MXR Dyna-Comp  
Seevink Translinear Squarer  
Roger Mayer Octavia  
Vox Suppa Tone Bender  
"Anderton" Ring Modulator  
MXR phase 90  
 
The Dyna-comp, Octavia, Anderton, and Phase 90 are also available other places, the Dyna and Octavia on the net.  
 
I was interested in the Orange Squeezer, Seevink (odd thing, that), and Vox Suppa Tone Bender; in fact, I have already laid out a PCB for the "Vox" and if it sounds good, may offer a PCB for it. I had the Orange Squeezer in my schematics library, as well as the Phase 90.  
 
"Rainbow" does have a layout for a hand-drawn repro of the univibe. I haven't checked it for accuracy, but JC's working from the right schematic, so it probably is OK. Lots of work hand drawing it, but it could be done with persistance and a good eye. It is somewhat unique in that it is not drilled at all, just has components "glued" to the traces by soldering the leads, kind of a retro surface mount.  
 
This should work OK; in fact, it's probably a good beginner technique, as drilling PCB's is the biggest pain about the whole process. I could wax philosophical about pcb processes, but suffice it to say that surface mounting standard parts works if you're willing to put in the effort to do it well.  
 
There's a hand drawn-able layout for the Phase 90, Small Stone, and a partial of the Mutron, although my photocopy was of chancy quality. These ones are all through-hole layouts, not surface mount. They will take some artistic talent, as they are the process that the Guitar Effects FAQ talks about, just take a circuit board pen and draw. My personal cut on this is that I'd rather do the layout work once and repro it with toner sheets, but that is only a consideration if you want more than one. The hand-drawn style works well enough for one copy if you're careful about layout and placing components.  
 
The effects building info contains a couple of useful tidbits, and a fair amount of info on switch circuits, and the NSL-32 as a replacement for the CLM6000.  
 
The data book pages are just that, photocopies of data book pages for various IC's and some general info from the National Semi Linear Data Book of a few years back.
 

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