Univibe and Fuzz recommendations

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Tek465b
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Re: Univibe and Fuzz recommendations

Post by Tek465b » Mon Jul 06, 2015 10:42 am

The blue fuzz codename is JH-F1, if that can help in any way.

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Froumy
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Re: Univibe and Fuzz recommendations

Post by Froumy » Mon Jul 06, 2015 4:22 pm

That does help, I thought he meant the mini. (that's why I was looking for one with a bigger enclosure)

One thing I found was that the bc108 has a gain of 500. Supposedly, a "preferred" range is in the 80-110 range, if you choose to match them. Cheap enough to mess with. Wondering if this lower gain per transistor, will translate better into the WC, than the high gain version.

Lots of good info on the forum vibe. 24 volts seems to be the preferred.

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Re: Univibe and Fuzz recommendations

Post by Xplorer » Mon Jul 06, 2015 4:35 pm

I disn't measure yet my bc108c, but they are possible tonfind on ebay, different ranges, i don't remember the brand right now but you should stick to it.

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Re: Univibe and Fuzz recommendations

Post by Tek465b » Mon Jul 06, 2015 4:59 pm

100-110 hfe for Q1, is mandatory. hfe for Q2 has very little if any effect.
Q1 is a current amplifier so its voltage gain is affected by the current gain(hfe) of that transistor and the emitter current.(+ nfb and the usual fuzz circuit working)
Q2 is a voltage amplifier. Change in hfe will change its input impedance but far from overloading Q1 output.. or doing any difference.
Last edited by Tek465b on Mon Jul 06, 2015 5:11 pm, edited 4 times in total.

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Re: Univibe and Fuzz recommendations

Post by Froumy » Mon Jul 06, 2015 5:08 pm

Excellent. Good to hear some confirmation on at least 1 range. Thanks.

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Re: Univibe and Fuzz recommendations

Post by springhead » Tue Jul 07, 2015 1:53 am

I built a Neovibe a few years ago. I used cells from Smallbear and the favoured Radio Shack bulb.
I bought 12 cells and selected 4 using a home made matching rig - an old pen tube in a clamp with a lamp at one end and the cell with an ohmmeter on it at the other!

I put mine in a box with a socket for an external speed controller (never got round to building that though). I put two foot switches on it - True Bypass and Cancel. Cancel stops the lfo, same as the heel down position of the original. Thats an important part of Jimi's sound at gigs where he used a vibe. He's playing through the vibe the whole time whether it's engaged or not. About 12 transistors in the signal path from memory.

Friend of mine is a very gifted Hendrix player with all original kit and bat ears. He has two original Univibes that I've repaired for him a few times. Both sound like Jimi but one is definitely better than the other. We A/B'd mine with his and it sounds identical to the better one of the two he has. Even to him! One of his uses carbon comp resistors, the other carbon film, mine is all metal film.

I don't know how much difference matching the cells made. Tweaking the wet/dry balance to get the best phase cancellation is very important though, and probably the main reason for the difference between his two original vibes. I also mounted the cells the same way as his - flat to the board and pointing straight up, not at the bulb. The 'light shield' - being a shiny metal box- acts as a mirror to ensure even light distribution across the 4 cells.

My chap also has an RM Voodoo Vibe which is extremely good. He gets the same result using an lfo chip rather than the quirky univibe oscillator.

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Re: Univibe and Fuzz recommendations

Post by Froumy » Tue Jul 07, 2015 7:59 am

Great info! What model cells did you choose?

How long did it take you for the build?

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Re: Univibe and Fuzz recommendations

Post by Tek465b » Tue Jul 07, 2015 8:56 am

Dont try making your own pcb for the neovibe, unless your experienced your better to get one online.
I did my own version of the pcb :).

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Re: Univibe and Fuzz recommendations

Post by springhead » Tue Jul 07, 2015 9:16 am

I bought the PCB from General Guitar Gadgets, took a couple of hours to populate/solder.

Time consuming parts are:

Planing/drilling/painting the box
Doing the off board wiring - all the pots/switches/connectors

Had to make a light shield out of thick foil, took a couple of goes (I used an oven ready chicken container!).
Final bit was tuning the wet/dry mix to get deepest phase cancellation.

Probably 6 or 7 evenings after work?

Fair amount of work but an excellent outcome. I know from being able to directly A/B with two original Univibes that it sounds completely authentic, and indeed better than one of those two.

Have a go if you've got the necessary time/ability. If you get stuck, RG Keen who published the Neovibe project many years ago frequents DIYstompbox and regularly answers 'vibe build questions.

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Re: Univibe and Fuzz recommendations

Post by Xplorer » Tue Jul 07, 2015 2:56 pm

best is to point the cells at the bulb and have at least an offset bias mod. the vt33n2 are good cells, also the NSL7532,
the bulbs : chicago miniature, 12 or 28 volts. you rather want the cells to be matched of course.
RG keen knows some things, but jc really is the univibe master and a very nice guy. his mu preamp may also be a cool thing to try.

http://www.lynx.bc.ca/~jc/

you can find his work into the forum vibe, or directly in his own Univibe + project. sadly, the original Mitsubishi transistors 2sc828 Q range from back then are nearly impossible to find, but according to JC it doesn't really matter. we did a tina ti simulation, fun stuff.

yes, exactly, the vibe with intensity down to zero, rather that switching it off with a true bypass, is something you desire ( along with a fuzz volume ), for Hendrix.
good thing to put two switchs on it, good idea.
i got a neovibe board but i'll probably never build it.
it can be tricky sometimes to build a vibe, and you can blow the bulbs, so better buy a few spares ..

the univibe is really a special one, many claim to sound like the original, but they all sound different and react differently according to the amp you're using. something out of the equation everytime, about Jimi / univibe, is , i think, the way he used his fuzz in front of it. anyway, i described it earlier.

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Re: Univibe and Fuzz recommendations

Post by springhead » Tue Jul 07, 2015 3:46 pm

In both the original Univibes I've repaired the cells are flat to the board looking straight up, so I did the same. Didn't try pointing them at the bulb on my build so I don't know what effect would be.

However the bulb ('Radioshack' favoured one) doesn't produce a spherical light pattern, particularly at lower intensities. It's more like a figure of 8. So to my mind pointing the cells straight up and using a light shield with effectively a mirrored inside surface ensures even light distribution across the 4 cells and hence good phase cancelletion. If it's good enough for the original 'vibes....

I agree the transistor choice isn't important in the audio stages. Think I mostly used 2N3904. You need something with sufficient gain in the LFO/driver circuit though.

Interesting project to build and tune, sounds amazing, not sure I'd like to build another!

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Re: Univibe and Fuzz recommendations

Post by Tek465b » Tue Jul 07, 2015 4:24 pm

I have some stock 2sc945 that was also used in the later shein-ei univibe. maby not the 2sc828 but they are good. tryed 2n3904 and 2n3588 i think not much difference
I simply removed the true bypass on my vibe, i just use the cancell and its not on cancel very often loll.
here some info about the univibe. you can see the ldr placement:
http://www.classicamplification.net/in/fof.html
The new bulb the filament is far away from the circuit because of the base/socket, i set the ldr flat but not all the way down on the pcb, i keep the same (ldr/filament)distance as the original.

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Re: Univibe and Fuzz recommendations

Post by Xplorer » Tue Jul 07, 2015 4:55 pm

interesting to see some variations of transistors.
but honestly, the cells flat, with or without glass protection, this doesn't matter actualy, this is fulltone marketting. i re sold this mini dejavibe very fast ... a joke of a vibe ..
but you can still have them flat, with a shiny enclosure, it'll be fine too. i'm just saying that most statements from fuller are a joke ...
having them facing the bulb can provide the best.
what matters is the speed of resistance reaction vs the light coming from the bulb and the oscillation circuit. AND a very large resistance range : these are the two main qualitys you want to look at for the cells.

a cool mod is to put a trimer affected to each cell, so you can adjust the resistance coming from each, for the audio circuit.
the offset bias mod is there to adequate the dark time and bright time of bulb with the cells, for the desired response in the audio circuit.

you can see a description here, with pictures explaining it :

http://www.lynx.bc.ca/~jc/pedalsUnivibe.html

the "magic" of the univibe is about a few electronic things that can be understood clearly, not about some hype concepts from fuller ;) , and i appreciate this article for pointing this out ! thanks

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Re: Univibe and Fuzz recommendations

Post by Froumy » Tue Jul 07, 2015 6:47 pm

You guys rock.

Pulled the trigger on the JHF1. Used, so I suppose it could be a crappy one, but none around here to try. With the original transistors having an average gain of about 90(as opposed to 108's 500), I'll be playing with them anyway. Hopefully I enjoy the 108's. Cheaper to build, but damn, I like that enclosure.

Big time thanks for the forum/neovibe stuff. JC recommends the Radio shack bulb, but looks like they're gone.
http://comingsoon.radioshack.com/1-5v-2 ... ZxKgkZa9wU

Springhead, do you recall which cells you used?

In reading, some say that any cell you get today, will be faster than the old ones. Read that 5 seconds after, there can still be 200 Ohms present. Good to know about the large resistance range, and trimmer.

Thanks for the time to build. Looks like this will go on the list of longer projects. Hopefully the fuzz helps push the vibe for a quicker build.

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Re: Univibe and Fuzz recommendations

Post by Xplorer » Tue Jul 07, 2015 7:52 pm

you got a blue fuzz ? cool !
but ... with no bc108c Inside ? what then ? i think that Dunlop uses some 200 - 300 hfe max on its blue fuzz, i should verify . yeah, the enclosure is very nice. this fuzz works nicely with a jtm45 base i think.
just try : zero fuzz gain, or max 2 . and volume at maximum.
then switch it on/off, you'll notice a part of the clue. now put that into a univibe with its intensity to zero ( but still on ) , and you'll get a better view. now compare this combo to full bypass of the fuzz and univibe. ....

and set you jtm45 to about : presence 9, basse 3 , mediums 7, trebles 8 , vol top left 7.

about the older original cells, they were faster, and less sensitive :

Original Uni-Vibe LDRs were made from a very different process (call it a different 'recipie' if that makes more sense to you) of Cadmium-Sulfide and they used a different layer width/thickness/dimension (notice the snake-like squiggles). They were faster response and less sensitive than new production cells. All the new production cells use a modern process/recipie and are easily spotted by their much skinnier patterns (notice they have more and thinner squiggles)

about the bulbs, look for these on Google :

Chicago Miniature "7371" 12v 40 mA
Or Chicago Miniature "2187" 28v 0,4 A

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