Univox - Univibe (Uni-vibe)

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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collingtech
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Post by collingtech »

awesome thanks mate

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JimSalabim
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Post by JimSalabim »

I have built a Forum-Vibe (vintage build: http://www.classicamplification.net/fv/ ... t2n_02.htm)
There is a treble loss in chorus mode (the vibrato mode is just fine).

Here’s a sound file (you hear the vibrato mode first, then the chorus mode):
http://matthiasstockert.de/forum-vibe.mp3

The intensity knob and the 500R trimmer are both fully turned to the right.

Any ideas?

Thanks in advance!

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JimSalabim
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Post by JimSalabim »

I have angled the LDRs more regulary and I think it’s a little bit better now.
Here’s sound sample (clean this time. First you hear the bypassed signal, then you hear the chorus mode):
http://matthiasstockert.de/forum-vibe_2.mp3

What do you think? Too much treble loss or is it normal this way?

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JimSalabim
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Post by JimSalabim »

Found and solved the problem. I had taken out the bridge rectifier and used a 9V DC power supply and a voltage doubler. These didn’t get the lamp bright enough. Now I’m using an 18V AC supply (now again with the bridge rectifier) and it works and sounds amazing. :-)

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Post by GuitarlCarl »

Well I have an original Univibe on my bench. Sadly no pedal. Unit doesn't seem to work, but do I need the pedal to fire this thing up?
With the LDR cover off I see a dull glow in the bulb, but no pulse. Flicking the power switch off and on shows a momentary brightness but nothing like I think it should be. Red lamped power bulb is also out but shouldn't effect the operations... Due to the age of the unit I'm guessing the electrolytic caps should all be replaced. I also see the LDR's are mounted flat, they're not angled in at all, but of course the reflector cover is mirror-like on the inside. It also does pass sound thru it and the volume does work, when I tried flicking the light from my cell phone at the LDR's (with the cover off) there was a pulse in the signal. So, before I've done any metering of the transistors, I've read everything I can find on the web, and here i am with a sick unit and no pedal. Can it run without the pedal?

Carl.
I want it to sound like bees buzzing around in a 55 gallon drum...

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Post by lolbou »

I would say no. The Speed potentiometer is in the very pedal...

I guess that's why the LFO is out. :wink:

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Post by Fastocker »

GuitarlCarl wrote:Well I have an original Univibe on my bench. Sadly no pedal. Unit doesn't seem to work, but do I need the pedal to fire this thing up?
With the LDR cover off I see a dull glow in the bulb, but no pulse. Flicking the power switch off and on shows a momentary brightness but nothing like I think it should be. Red lamped power bulb is also out but shouldn't effect the operations... Due to the age of the unit I'm guessing the electrolytic caps should all be replaced. I also see the LDR's are mounted flat, they're not angled in at all, but of course the reflector cover is mirror-like on the inside. It also does pass sound thru it and the volume does work, when I tried flicking the light from my cell phone at the LDR's (with the cover off) there was a pulse in the signal. So, before I've done any metering of the transistors, I've read everything I can find on the web, and here i am with a sick unit and no pedal. Can it run without the pedal?

Carl.
The LFO won't function without the speed pot connected . . . so yes, you need a pedal. Make sure you try the unit out with a pedal first before you go swapping any components . . . it might not need much work.

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Post by mictester »

I lashed up a test pot for Univibes using a dual 100k linear pot. Worked a treat (but I can't find it now!).
"Why is it humming?" "Because it doesn't know the words!"

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Post by mictester »

mictester wrote:I lashed up a test pot for Univibes using a dual 100k linear pot and a DIN plug. Worked a treat (but I can't find it now!).
"Why is it humming?" "Because it doesn't know the words!"

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mictester
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Post by mictester »

I lashed up a test pot for Univibes using a dual 100k linear pot and a DIN plug. Worked a treat (but I can't find it now!).

It's worth noting - some Univibe oscillators will work with the pedal unplugged - but very slowly!
"Why is it humming?" "Because it doesn't know the words!"

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Post by DrNomis »

I've found that a dual 250k pot also works as the speed control, the speed of the effect at lower settings is slower... :thumbsup


One thing you do need to be careful of is plugging in the speed control pedal when the Univibe is powered up, if you inadvertently do that you run the risk of instantly frying the LFO transistors, I found that out the hard way, so, first make sure you have the speed control plugged in before you power-up the Univibe..... :thumbsup
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GuitarlCarl
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Post by GuitarlCarl »

IT'S ALIVE!
Imagine that, the pedal which completes the circuit.... makes all the difference.
Spent the last two hours playing the thing. Into a Rat, sounds great. Into a Muff clone (starcaster distortion) sounds freakin' awesome. I took a little time to try and dial in the same sound into my DOD VibraThang, with one there to listen to I can get it pretty close, but I'd have never found the sound without the real thing to compare to. So since this pedal isn't mine... I guess I've got to build one, the pedal for the speed is what the VibraThang is missing, and it's not quite as liquid in the rolls, I don't know how else to explain it.

Image

You guys rock thanks for all the help...

Carl.
I want it to sound like bees buzzing around in a 55 gallon drum...

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DrNomis
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Post by DrNomis »

mictester wrote: 01 Sep 2015, 13:49 I lashed up a test pot for Univibes using a dual 100k linear pot and a DIN plug. Worked a treat (but I can't find it now!).

It's worth noting - some Univibe oscillators will work with the pedal unplugged - but very slowly!

I had a good look at the LFO circuit in the UniVibe schematic, it looks like an old-school version of the classic phase-shift oscillator as found in some Fender Tremolo circuits, in the case of the UniVibe it uses transistors rather than 12AX7 Tubes.
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.

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