# ElectroVibe Mini/"MonkVibe" Prototype



## Big Monk (Mar 15, 2022)

I've been working here and there on a design for a revised and slightly re-imagined UniVibe circuit. 

@Chuck D. Bones has given me some design elements, with a reworked Opamp front end in particular along with several other improvements, based on talks we have had.

My plan is to do some R&D and testing using the E-Vibe Mini as a platform. I have a pretty good working cross reference sheet started so that I can use the E-Vibe Mini parts list and the Big E-Vibe schematic together.

While I can't do the Opamp front end on the E-Vibe Mini board, I can implement pretty much all the other circuit mods involved with minimal tweaking. The stuff I plan on doing are as follows:

1.) Substitute the 2N5088s for true MPSA13 Darlingtons in all stages and re-bias the stages accordingly
2.) Tweak the phase mix resistors for perfect balance
3.) Ditch the charge pump circuit and inject 24 vDC directly to the regulator
4.) Increase the Series LDR caps to 10 uf to increase phase notch presence/depth
5.) Add a 330 ohm/1W resistor in series with the lamp for overcurrent protection and ease stress on bulb and bulb driver Darlington
6.) Enhance the upper and lower speed limits. the 24 vDC powering the LFO along with these changes will vastly improve slow speed depth
7.) Use the externally adjustable 3362P trims for Bias and Gain
8.) Try out a "Cancel" switch for access to the preamp by itself

This will be an effective prototype for what I'm calling the "MonkVibe", which will have the opamp preamp and a faux "Cancel" switch that routes the I/O through a duplicate preamp instead of standard "Cancel" mode.


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## cooder (Mar 15, 2022)

Sounds very cool! As a self confessed UniVibe addict I'm looking forward to following what you cook up there and your findings! 
Only thing that I wonder wouldn't it be better to try powering from 18VDC as a good number of quality PSUs offer that as a voltage. Otherwise there would be another blimmin wall wart....


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## Big Monk (Mar 15, 2022)

cooder said:


> Sounds very cool! As a self confessed UniVibe addict I'm looking forward to following what you cook up there and your findings!
> Only thing that I wonder wouldn't it be better to try powering from 18VDC as a good number of quality PSUs offer that as a voltage. Otherwise there would be another blimmin wall wart....



The goal is to get close to the original Univibe voltages. My research seems to indicate that this is a less understood but powerful part of the original's rich depth at slow speeds.

My plan is to try both but with wal-warts. I don't think the tightly controlled 18 vDC from a charge pump is sufficient to get where I want to be.

Part of it is that the original actually generating more than the 24 vDC it's transformer would indicate. A wal-wart, lightly loaded is going to produce higher voltages, which research indicates provides that rich, swirling slow speed tones.

A 24 vDC wal wart is likely to output 29 vDC at loading typical of the vibe circuit and an 18 vDC adapter somewhere close to 24 vDC. 

I think that's going to be key.


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## fig (Mar 15, 2022)

Big Monk said:


> A 24 vDC wal wart is likely to output 29 vDC at loading typical of the vibe circuit and an 18 vDC adapter somewhere close to 24 vDC.
> 
> I think that's going to be key



We'll wait for an electrical storm.....I'll prepare the electrodes [drags foot]


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## Big Monk (Mar 15, 2022)

fig said:


> We'll wait for an electrical storm.....I'll prepare the electrodes [drags foot]



What I’m chasing is that very slow churning, rich, deep swirl you hear on “Breathe”. 

You can tell he’s got the Speed very slow which on even my Big ElectroVibe seems to elicit less oomphy, swirling vibe tones than that. 

Anyway, it’s worth a shot. I have an 18 vDC tap on my CS7 so worst case I can power it off that.


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## Gordo (Mar 15, 2022)

I'm looking forward to this Monk, I upped the gain but did nothing else to my vibe and closed it up again.  Color me a vibe freak though...


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## zgrav (Mar 15, 2022)

Subbing the MPSA18 for the 2n5088 feeding the lamp makes a significant difference in the lamp range of bright to dim I get when running on the charge pump.  It will be interesting to see what you get replacing all of the 2n5088s and run at the higher voltage.


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## Big Monk (Mar 15, 2022)

Gordo said:


> I'm looking forward to this Monk, I upped the gain but did nothing else to my vibe and closed it up again.  Color me a vibe freak though...



I just want to see how these mods affect e richness of the Vibe. It’s an experiment for sure.


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## Big Monk (Mar 15, 2022)

zgrav said:


> Subbing the MPSA18 for the 2n5088 feeding the lamp makes a significant difference in the lamp range of bright to dim I get when running on the charge pump.  It will be interesting to see what you get replacing all of the 2n5088s and run at the higher voltage.



Part of the restructure to MPSA13 was to save on some transistors, i.e. the actual amount. In my “production” unit, for lack of a better term, I’m using a single board and KOA Speer miniature 1/4 w resistors to save space. 

The re-biasing of the phase stages was all @Chuck D. Bones idea. He gave me some great feedback when I originally tapped him for support.


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## Feral Feline (Mar 21, 2022)

fig said:


> We'll wait for an electrical storm.....I'll prepare the electrodes [drags foot]











Very cool, Big Monk, I look forward to following your discoveries on this latest adventure.


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## Raspymcnasty (Apr 12, 2022)

Any updates monk? I’m eagerly awaiting your results. I too am searching for the deep sweep from ‘breathe’


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## Big Monk (Apr 12, 2022)

Raspymcnasty said:


> Any updates monk? I’m eagerly awaiting your results. I too am searching for the deep sweep from ‘breathe’



I just started designing the board today so it’s not there yet but I’ll be test driving some stuff in a prototype built on the ElectroVibe Mini in the next few weeks.

I’m going to order one of the EHX 24 vDC/100mA power supplies this week to test with.


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