UVICS - Univibe In a Crybaby Shell

[RedHouse]

Something else.
UVICS part # R 49 and R 50 are 47K
In the other Vibe schematics these are 4k7.
Is 47K correct or a typo ?

R49 (UVICS) should be 4k7, that's an old internet mistake that won't go away. Here's the resistor, it would be numbered R46 in the original schematic:




As for R50, well if R47 wasn't there, then R50 would be 47k.

Although R50 is not part of the traditional univibe schematic, RG will have to chime-in with his thoughts on why he has it that way here.

Yeah sorry, I missed where you said you tried different R1 values, the only case I've ever had where I couldn't dial-out farty-distortion on the input was with a bad batch of 2N5210's. Once I bought a batch (300, from Mouser) and like every single one had that weird farty distortion.

Hey Brymus, here is a video clip DaveFx did on adding a LED (JC Maillet style) to one of my Vibe-Baby's, he used a high brightness Blue LED, I think it looks kind'a cool myself:

http://www.lynx.net/~jc/DaveForeman-UnivibeSpeedIndicator.mpg

Dave put his LED on the side of the wah-shell, so it kinda shoots across the floor.

[R.G.]

UVICS part # R 49 and R 50 are 47K
In the other Vibe schematics these are 4k7.
Is 47K correct or a typo ?

That's an interesting question.

I started to just blap out an answer and then I remembered that I did most of the stuff on the Neovibe so long ago that the details were not as sharp as they should be. So I did some looking at both my schemo archive and some hand-drawn notes I made from working on 'vibes over the years. R50 should be 47K, although this doesn't matter nearly as much with a bias trimmer as it would if the bias was fixed.

R49 is not so clear. The various copies of the factory schemo I've found over time show it as 47K. For instance: http://www.univox.org/pics/schematics/univibe.gif and  http://www.univox.org/pics/schematics/univibe1.jpg

Yet I had it at 4.7K in the Neovibe at one point, and at 47K at other times. It's possible that I'm color blind enough not to distinguish red bands from orange ones, I guess.  But my personal confusion became clear when looking at my notes on the originals I've fixed.

I've seen it both ways in the originals, according to my notes. Including looking for evidence of resoldering and measuring values by meter.

Lest this be thought to be some kind of mistake that just won't go away - like my getting one of the caps reversed on the very first layout of the vibe clone that became the Neovibe, which really was a mistake that can't be stuffed back in the box, I also did some looking at the circuit work I did on this the last time I messed with it.

Turns out they both work; which is good, because different production runs of the "original" had both at different times, by measurement. Why they work is the question. I think that it depends on how hard you want to run the lamp driver. The lamp driver is a weak spot in the circuit; it was the single most common repair I did. As a pure guess based on seeing how field problems get fixed in manufacturing, I suspect that it may have been 4.7K early on, and they had lamp driver failures; it may have been changed later for that reason. Or some other. This is the purest speculation about why a resistor change could have been done. The emitter resistor was changed a few times, as well. I've found 22, 100, and 150 in the ones with a trimmer. I repaired one which had a 68 ohm and NO trimmer in the driver emitter.

So - which one is correct? They both are. I've seen them both in factory units.

Try it and see what you like. They will give different drives to the lamp driver. This will matter more with a single transistor bulb driver than it will to a darlington, because the input impedance of the darlington is so high it will respond more to voltage on its input, while the single device will eat more current, and also act more like a current amplifier. The real test is whether it can drive the bulb to a brightness change that makes the LDRs work.

Hmm. Now that I say that, I wonder if the bulb driver life was all that drove the changes, or if they got different batches of LDRs over time. Could be. That is guessing, just like the guess at why they'd change the bulb driver resistors. Fortunately, we have the freedom to adjust to taste. The bulb light variation and how it matches the LDR sensitivities is what matters to the sound, by controlling the phasing. How it gets there is kind of immaterial as long as it does get there.

[Brymus]

An update:
I added two more diodes to the stack.(raised pre amp V above 15)
Havent noticed any farts.

Added the ground jumper and cut the one I added to the header.
LFO thump is not noticable now.

Halved the 3 LFO caps to .47uf and raised R40 to 4m7   
The speed stayed the same as far as I can tell.
It wasnt what I expected,I expected it to get slower and faster at the min and max.

I tried the LFO indicator.
I cut the trace right after the bulb before the Vreg.
I used a ultra bright blue.
But with it trimmed right to flash it was really dim. (too dim to be usable without being in line of sight)
I could no way get it as bright as the blue one in the vid Brad linked to and still have it flash.

I then noticed RG has the LED before the bulb,I wonder if that matters.
I want mine to flash blindingly bright so it shows from under the treadel.

Weird thing with the trace cut and nothing hooked up,the bulb still flashed.
How is that possible?


I socketed the 4 phase caps,will play with those tonight.

Before this last round of mods I spent quite a bit of time playing songs from "Dark Side of The Moon"
And it was excellent,I never knew thats how Gilmore got "that" sound.

[R.G.]

I'll take a look.

[RedHouse]

...
Weird thing with the trace cut and nothing hooked up,the bulb still flashed.
How is that possible?

Wrong trace or perhaps a solder-bridge somwhere?.

If the trace was cut between the bulb and v-reg the bulb should not light (at all) without the LED/trimmer connected.

...But with it trimmed right to flash it was really dim. (too dim to be usable without being in line of sight) I could no way get it as bright as the blue one in the vid Brad linked to and still have it flash.

I'll send DaveFX a message and see if he has some time to chime-in here on how he did his in the video.

[Brymus]

Hey Brad
If you look at the PNP
I cut the trace between the Bulb's square pad and the Vreg.
That leaves the bulb connected to power in (square pad) and Q13 (round pad),which is why it still blinks.
This basically just cuts power to the rest of the circuit when the LED/trimmer is not connected.
Like you showed to do.

In RG's latest update he shows cutting the trace bewteen Q13 and the bulb's round pad.

At least thats my understanding ,I may be wrong.

[Brymus]

I just spent two hours looking for some info about the Univibe and mods.

I found it in a copy of Brad's forum vibe PDF that someone posted to the net (you have to e-mail Brad to get it)
I think you would get alot more kudos if you just posted that PDF Brad really good info in there.

I gotta say between the "technology of" at GEO ,JCM's page that Brad linked to earlier and the info in Brad's PDF
Its all there.
Also some of JC's older posts here contain alot of good info on shaping the LFO and such.
And also on adding an LFO indicator.

[RedHouse]

I just spent two hours looking for some info about the Univibe and mods.

I found it in a copy of Brad's forum vibe PDF that someone posted to the net (you have to e-mail Brad to get it)
I think you would get alot more kudos if you just posted that PDF Brad really good info in there.

I gotta say between the "technology of" at GEO ,JCM's page that Brad linked to earlier and the info in Brad's PDF
Its all there.
Also some of JC's older posts here contain alot of good info on shaping the LFO and such.
And also on adding an LFO indicator.

Thanks for any kind words Brymus.  

The Forum-Vibe PDF's all had errors, no matter how hard I tried and I re-did it like 4 times since the first one in 2005 and people still found errors ...sooooo... I bit the bullet and did it with webpages now which are instantly editable and everybody is "on the same page" so to speak.
(error were in the documentation only, not the PCB layout)

The new, improved (ie; less mistakes than before) Forum-Vibe docs are here: http://www.classicamplification.net/forumvibe/ no more PDF's, if you have one and go by it, know that there are mistakes and ...you're on your own.  

The webform you fill out (if you want to receive the v3 layyout file) gets you a PDF, but it's only the toner transfer pattern, no other documentation because doc's are all on the website now.

If you look at the PNP
I cut the trace between the Bulb's square pad and the Vreg.
That leaves the bulb connected to power in (square pad) and Q13 (round pad),which is why it still blinks.

Hmm, I'm not seeing that. In the files I'm looking at the power rail comes from the big caps, tags Q12 and Q13, then travels up to the sq-pad for the bulb, then to the sq-pad on v-reg.

The way I'm seeing it if you cut the trace between the sq-pad (bulb) and the sq-pad (v-reg) you loose power to the rest of the board, am I needing new glasses again?

[John Lyons]

I bit the bullet and did it with webpages now which are instantly
editable and everybody is "on the same page" so to speak.

Oh, didn't catch that Brad.
I'll pull the PDFs I have on line so there is less clutter
and your web pages can be the main documents.
Carry on folks.
Nice work Bryan!  

EDIT:
Hey! The site pages for the Forum vibe look sharp Brad!
Nice work on those. Comprehensive! 

[RedHouse]

I'll pull the PDFs I have on line so there is less clutter

Probably best, thanks John.

[R.G.]

The way that looks simplest to me is to put the LED in series with the lamp. The lamp pulls a current between 0 and probably 25-40ma. This is very close to the current range for an LED. It's too high at the top end, and may not go all the way to zero. That makes it desirable to pass some current around it so the LED is not passing it all. A resistor can do that.

I'll do a bit of simulation and make some recommendations.

[Brymus]

@Brad
Yeah I hooked it up like the pic you posted.
It still works just not as bright as I wanted.
And the way I see it without the LED and trimmer the rest of the board would lose power that way.
So yes.



The best way is probably like RG shows in the UVICS 3, in series before the bulb.
I also tried in series with R46 it was still really dim.

Has anyone tried what I think is called regenerative feed back ?
I read a post by Mark Hammer from 04' saying something about a 100k pot and a small cap from output to input.
And that it either sounds great or horrible.
Can anyone report on trying this ?

[Brymus]

Ok I tried it.
Its pretty cool .
I used a 500K pot.
For a small cap like 470 it can go as low as a few ohms without complete oscillation/feedback.
The larger the cap the more resistance you need to keep it usable.

But it really does add some depth to it,much more phaser like.

That combined with some switchable tone caps can really open up the sonic pallet in the vibe.

[RedHouse]

Ok I tried it.
Its pretty cool .
I used a 500K pot.
For a small cap like 470 it can go as low as a few ohms without complete oscillation/feedback.
The larger the cap the more resistance you need to keep it usable.

But it really does add some depth to it,much more phaser like.

That combined with some switchable tone caps can really open up the sonic pallet in the vibe.

Yeah, the feedback thing (IMO) takes it away from "vibe" zone and into the Phase-90'ish realm. I even had switchable caps to bring it closer but I don't use feedback on my vibes because I feel it's better to use a Ph-90/Ross for that tone.
(and besides, they do that sound better anyway)

As a side note, years ago I used to try to make/build things into the proverbial "one size fits all" (ie, had an SG that tried to do Zeppelin and Hendrix tones with an HSS topology, a JCM800 with plexi mods switching etc) but the tradeoffs always end up getting nothing "nailed" and everything "almost" there, so I changed my approach in favor of using the right tool for the job. Yeah it means more gear, but the tone is "there" when you need it, no compromise. YMMV

The best way is probably like RG shows in the UVICS 3, in series before the bulb.

IMHO, and not meant negatively, the best way is using separate power traces in a vibe layout so you can mess with the bulb (and LFO section) separately from the audio section power, but that's only my opinion.
(ie; my Vibe-Baby, Classic VIbe, and Forum-Vibe all use that topology)

Doing so allows one to have the original format, or the modifed v-reg format, and manipulating the bulb without effecting the rest of the circuit. Unrelated to this UVICS layout, I supply a 2-pin header on my boards (only to certain customers) that allows the easy addition of the JC-LED-mod, if the end user chooses not to utilize that option a simple jumper like the kind you find on a computer motherboard is placed on that 2-pin header. I did make this suggestion earlier and it was not welcomed, but it is a very cool option and makes it easy to add/delete the LED for the end user.

[R.G.]

IMHO, and not meant negatively, the best way is using separate power traces in a vibe layout so you can mess with the bulb (and LFO section) separately from the audio section power, but that's only my opinion.
(ie; my Vibe-Baby, Classic VIbe, and Forum-Vibe all use that topology)

I think I agree with a statement you've made before - rearranging the traces on an existing PCB layout isn't really up to the level of being design work. It's no biggie.

When Bry has a light/indicator he likes, I'll drop it in. Takes under 10 minutes to rework the layout for things like that, including rebuilding the PDFs.

Not meant negatively, and as you're not doubt aware and will agree wholeheartedly with, the whole issue of increasing flexibility necessarily increases complexity. Adding options means adding space and extra pads and traces; in the limit, the layout becomes perfboard - absolutely flexible, but maximally complex for the person who puts it together. And with maximal possibilities for customization inherently comes maximal opportunities to make mistakes. It's very much a two-edged sword.

Someone choosing only the good mods is always open to interpretation. If less that every possible mod is included, then there will inevitably be builders who want the ones that were left out in the interests of simplicity, no matter what.

Shrug. One man's ceiling is another man's floor.

I can always do a maximal-modder layout incorporating spaces for every possible mod, option, and tinkering/setting option. You know, now that I think of it, I'm pretty sure I have the eight-stage vibe with stereo outputs layout still in the archives. No biggie.

What do you think, gentle readers? And be careful what you ask for - you just might get it... 

[RedHouse]

You crack me up sometimes RG (well ok, most of the time).
Nice bit of "trace pushing" if I do say so myself...

 

and a few more...

 

Hey, you should post some pic's of yours!.    

Peace out.

[R.G.]

You crack me up sometimes RG (well ok, most of the time) when you do a vibe layout you're "designing", everybody else is just "pushing around traces".

And you crack me up sometimes, you kidster you. 
I was referring to the direct quote below that I believe you wrote in the forum vibe stuff that someone emailed to me:

It isn't a new design, unless you tend to call reworking a PCB layout designing (which I don't),

I kind of agree with you on that. I think of design as a much more enlightened and demanding activity. But I don't much care what we call PCB redesign. Some PCB work is closer to crosswords and doodling, some takes attention and focus. Shrug. I'm good with calling PCB work design or not, whichever you'd prefer. You pick, I'll call it that. How much fairer could that be? 

Hey, you should post some pic's of yours!

No need to. 

It's all good. Peace, love and purity of essence, campfires, and  - well, you know. 

[Brymus]

I can always do a maximal-modder layout incorporating spaces for every possible mod, option, and tinkering/setting option. You know, now that I think of it, I'm pretty sure I have the eight-stage vibe with stereo outputs layout still in the archives. No biggie.

What do you think, gentle readers? And be careful what you ask for - you just might get it...  

Seriously ?
Oh  sh!t yes !!!!!
In my researching the univibe I have seen people asking you to show your omni vibe for years,in different forums.
I for one would love to see what that modder deluxe 8 stage vibe would look and sound like.

[phector2004]

Sounds awesome!

Will it incorporate a toggle switch to return to normal (4-stage?) mojo-riffic Univibe mode?

More importantly,

Is it illegal in any states? 

[R.G.]

Will it incorporate a toggle switch to return to normal (4-stage?) mojo-riffic Univibe mode?

It's back to the flexibility/complexity tradeoff. That was not a joke.  The real problem in all this is deciding what to put in and what to take out.

More importantly,
Is it illegal in any states?

It's not illegal in Texas. Maybe California. 

And it's almost certain to be a federal offense to take one across a state line.