Univibe Build

[Spencerleehorton]

Just making a note that the univibe current draw is about 35mA, 0.035A

 

[CJH]

I’ve reboxed this original circuit univibe, I’ve put in several mods, speed mod, changed middle 1uf to 2.2uf and changed 4.7k resistors to 1.5k. Now it’s an acceptable fast speed and nice slow speed.
I’ve changed the 47k on the input (after the first 22k) to 2.2M and changed the 3.3k to 7.5k on the 3rd transistor collector and now have plenty of volume between effect on and off.
True bypass and I have also put in the 50k pot with 68k on each leg with the wiper going to the chorus/vibrato switch, taken out the two 100k resistors.

The problem I’m having is setting up the bulb and the LDR so that the effect is more prominent, on chorus it sounds nearly there depth wise but on vibrato on slow speeds the effect is really difficult to hear.
The other problem is I can hear the robot the bulb, almost like there is an earth problem?
And help on getting the effect more prominent and getting rid of the bulb noise would be appreciated!!

Here is a good link to schematics etc

https://musikding.de/docs/web/univibe-ForumVibe-final.pdf

"the effect is more prominent"

I've Got a Moen Shaky Jimi which has brought the concept into the 21st century, it uses LEDs and LDRs, one widely used "mod" (to achieve the goal you list,)is to Light shield each individual LED-LDR PAIR. so there is no cross talk with other LDRs in the circuit. Black electrical tape being the "Mod"

 

[CJH]

"the effect is more prominent"

I've Got a Moen Shaky Jimi which has brought the concept into the 21st century, it uses LEDs and LDRs, one widely used "mod" (to achieve the goal you list,)is to Light shield each individual LED-LDR PAIR. so there is no cross talk with other LDRs in the circuit. Black electrical tape being the "Mod"

may be start by painting the inside of your Kinder egg dome Flat Back to minimize reflected light?

 

[Spencerleehorton]

I thought the idea was to have as reflective surface as possible inside?

 

[Spencerleehorton]

Got this one working now, and there is a few mistakes on the layout picture mainly 2 transistors are labelled with the legs in wrong position, no case for this one yet so good old buzz with it at the moment, the effect sounds excellent on the chorus and vibrato.
Best sounding univibe yet.
I’ve used 2n3904 for Q1 and Q11, 12, 13.
All others are 2N5088.
Silonex LDR
B250k dual pot for speed
All resistors as per original schematic apart from one 47k which is 100k?
Don’t know it’s different but on this layout it is?
Will identify which one it is.

 

[Spencerleehorton]

I’ve bought a Hammond 1550GBK which is 222mm x 146mm x 51mm to house it all in.
I’m quite surprised on how many schematics are incorrect and I’m starting to doubt if there is actually a correct one!!
Every schematic seems to have slight differences?

 

[Spencerleehorton]

I have checked this all a few times and this is what i believe to be the correct univibe schematic, well at least its correct to what i have on my univibe B Shin-EI pcb, which if i can get the PSU correct along with GND so no hum it should sound amazing!!

 

[dai h.]

I thought the idea was to have as reflective surface as possible inside?

The previous link to (one of) Hendrix' Univibes repair thread showed a cardboard cover.

On the Classic Amplification "Fact to Funk" (sort of a Univibe mythbusting page), "Bunk #5 - A Shiny Cover", he talks about this (bit lower than halfway down the page--unfortunately some pictures are missing from the wayback machine version of the page) :

https://web.archive.org/web/20190729202914/https://classicamplification.net/info/ffwtf.html

re: the noise if it's not a fault with the build maybe a problematic ground loop arising from the additional AC safety ground for the Univibe (which should stay for safety IMO). If that is the problem, maybe look into this (section 15.10: Ground Lift) :

https://www.valvewizard.co.uk/Grounding.pdf

(also this from Elliott Sound Products--which goes into a bit more detail with implementation) :

https://sound-au.com/earthing.htm#s9

(Fender used this in the reissue 6G15 Reverb (with isolated jacks). Also 15 ohms instead of 10 ohms and no 100nF cap.)

https://schematicheaven.net/fenderamps/63_reverb_manual.pdf

Also (for a different route) there should have been a transformer signal isolator (DIY) project on R.G. Keen's site (GEO) and somebody (on amp garage BBS IIRC) did a teardown of a Suhr (commercial) one. If memory serves an inexpensive 1:1 (600 ohms: 600 ohms?) one was sandwiched between opamps (I gather it was to ensure a consistent result by having a certain driving impedance and termination. And maybe to get better low frequency response by driving the primary with the low impedance from an op amp. Also less windings = better HF response?--something like that).

 

[Spencerleehorton]

well as i thought sucess would be slow in coming but has arrived!!
I have a laptop power supply which gives me 19.5vdc so i thought to myself why dont i bin the transformer inside the case arrangement and just have a DC socket on the side just feeding after the diodes.
I swapped the footswitch for a new one, may add the blinking LED at some point for the speed and intensity, connected the laptop psu and closed the case, no hum, just a very slight bit of bulb noise which tbh is perfectly acceptable and a tiny bit of hiss from the unit which i would totally expect due to the circuit.
Pedal sounds amazing now, so as far as im concerned putting the transformer inside the case is not happening and i will just purchase another laptop psu for the Shin-Ei version and do the same trick.

 

[Spencerleehorton]

and by the way i used some left over mumetal to make the light cover and it just happens ive used the less shiny side inside and the shiny side on the outside as per the recommendation on that fact or funk univibe site.
i used a red LED for the on light and used a 1.8k drop resistor, 19vdc -drop 17v @ 0.010A (10ma) = 17 / 0.010 = 1700 but 1800 is close enough!!

 

[Spencerleehorton]

If I use a LED in series with the lamp and put a 500R trimmer in parallel with it, apparently that is how to do the speed led, not much more info that that at the moment but I’ll try it and see if it works.
Also got to put in the 250k trim for the bias on the Shin Ei pcb.

 

[Spencerleehorton]

I now have 4 univibes but only one working how I want it too which is my vibe A, pretty sure this Shin Ei vibe will be fine, the other two mad bean versions need some attention to get to be as good as this vibe A, now I feel I have all the info need to get them all working correctly.

 

[scondon]

I now have 4 univibes but only one working how I want it too which is my vibe A, pretty sure this Shin Ei vibe will be fine, the other two mad bean versions need some attention to get to be as good as this vibe A, now I feel I have all the info need to get them all working correctly.

Please let us know what changes you end up making to the madbean versions.

 

[Spencerleehorton]

Well the first change will be to use the B250k pot for speed along with 1.5k resistors rather than 4.7k.
I will also make another mumetal light shield.
Using some good LDRs will improve the FX amount
Setting the lamp brightness and bias point of the bulb I’m much better at now.
I have harbinger one and two, so will go through schematic and check everything is as it should be.

 

[InterstellarObscure]

No I haven’t? Is this something you know about?

I heard mention of it, but no detail. It's something I've wanted to try out for a long time; see how it does with envelope following and different control shapes. Sorry for the tangent.

Make the dual-pot a dual-optocoupler and control the LED current.

I'll give it a try with vactrols, thanks kindly

 

[Spencerleehorton]

Sorry I know what you mean now!!
Yeah the harbinger two has that, I’m in the process of tweaking mine

 

[Spencerleehorton]

Here is a quick video I’ve done of the vibe b version.



Also to make note that best LDR I’ve used and found are the silonex NSL-7530.
Ordered them from RS but others may do them.

I’ve also tried out some other LDR of the smaller size, I’ll find where I bought them from and put that info up.
What I have noticed is that they have a dark resistance of about 2Meg and light response goes down to 300ohm so good variation.
I put these is another univibe I had and the effect was great, lots of effect and they were pretty cheap, only about £2.50 each.

Here is where I got them

https://www.musikding.de/Photo-cell-8k-20k-1M

They work great

Here is the spec on the GL5528

https://www.techonicsltd.com/product/gl5528-light-sensitive-resistor-ldr-8k-20k-ohms/