ElectroVibe Modifications Thread

For any one interested, here's the diagram at the beginning of this thread color coded by the mod. I'm looking at this project and the colors help my brain.

View attachment 25071
is C7 supposed to be 10u as well? @bigmonk

So far I have the following mods noted.
R4 - 2M2 - Unity vol mod
R12 - 5M - Slow speed mod
R14/R15 - 2k7 high speed mod
C7/C10/C13/C15/C21/C23/C24/C26 - 10 uF - Low end mod
Q3/Q4 - 2N3904 - Reliability mod
Q14 - MPSA13 - darlington final phase stage mod

does this all look correct? or any suggestions for testing?
 
I just wanted to double check since the explanation on the image on the first page explained you did it to C7 as well. Do my mod listings above look correct? Thank you btw.

That’s a direct quote from R.G. Keen, not me.

The caps noted specifically on the drawing and refdes are the ones to change because they actually correspond to the Electrovibe.
 
A couple more questions about mods. (Sorry I am hijacking this thread for my personal interests. Let me know if I should delete this post and start a new thread.)

I am interested in these mods: Unity Gain, Min/Max Speed, Low End & 2nd Phase, Phase Mix & Reliability & Darlington. There is no reason these can't all be implemented at the same time, right?

For the Min/Max Rate Mod, a resistor of 5M or above at R12 for extended range at slow speeds? Has anyone experimented with these values?

For the Phase Mix Mod, it is having one end of R16 & R17 connected to the board, connecting the other ends to a lug of 50k trim pot, then another leg of the trim pot back to the open R16 & R17 pads?
 
A couple more questions about mods. (Sorry I am hijacking this thread for my personal interests. Let me know if I should delete this post and start a new thread.)

There’s a lot to unpack here. I’ll do my best.

I am interested in these mods: Unity Gain, Min/Max Speed, Low End & 2nd Phase, Phase Mix & Reliability & Darlington. There is no reason these can't all be implemented at the same time, right?

Unity gain is a no brainer and only a single resistor swap. Min/Max speed is also a resistor only mod. The cap mods are simply component swaps. Single resistor to Darlington swaps are straightforward as well.

For the Min/Max Rate Mod, a resistor of 5M or above at R12 for extended range at slow speeds? Has anyone experimented with these values?

Not that I know of. That’s directly cribbed from J.C. Maillett.

For the Phase Mix Mod, it is having one end of R16 & R17 connected to the board, connecting the other ends to a lug of 50k trim pot, then another leg of the trim pot back to the open R16 & R17 pads?

What would I do? I would get 2 75k ohm, 1/8w resistors. I’d attach each of them to the outside lugs of a 50k trim, along with a clipped lead attached to the wiper.

Find the junction of R16/17. There will be two acceptable pads to attach the wiper to. Attach the 1/8w resistors to the other ends of R16/17.
 
There’s a lot to unpack here. I’ll do my best.
You did great thank you! Yes those component swaps are easy to grasp.

What would I do? I would get 2 75k ohm, 1/8w resistors. I’d attach each of them to the outside lugs of a 50k trim, along with a clipped lead attached to the wiper.

Find the junction of R16/17. There will be two acceptable pads to attach the wiper to. Attach the 1/8w resistors to the other ends of R16/17.
What is the "junction?" Is the wiper the center lug of the trimmer? As in:
 

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A stock ElectroVibe is like a stock Valve Junior: There are only a few things you HAVE to do to get it to sound great.

Honestly, Unity Gain and faster max speed are the only things that really beg to be done. It’s awesome with just that.
Good to know!
 
You did great thank you! Yes those component swaps are easy to grasp.


What is the "junction?" Is the wiper the center lug of the trimmer? As in:

R16/R17 is a voltage divider.

The phase mix trimmer, along with the fixed resistors, replaces this divider.
 
R16/R17 is a voltage divider.

The phase mix trimmer, along with the fixed resistors, replaces this divider.
Oh I see. Thanks! I was wondering about how to physically implement the mod. Maybe I'll skip this one if it doesn't make a noticeable audible difference.
 
Maybe I'll skip this one if it doesn't make a noticeable audible difference.

It does. Worst case, just tack in the assembly and then use fixed resistors of the values:

New R16 = 75k + Rleft
New R17 = 75k + Rright

Where Rleft and Rright are the values measured from wiper to left lug and wiper to right lug after you’ve found the best null setting (strongest phase tone).
 
It does. Worst case, just tack in the assembly and then use fixed resistors of the values:

New R16 = 75k + Rleft
New R17 = 75k + Rright

Where Rleft and Rright are the values measured from wiper to left lug and wiper to right lug after you’ve found the best null setting (strongest phase tone).
Oh It does? Hmm. I'm just not knowledgeable about the basics to understand what to do here.

In post #97 you said to build this (pic attached) then "Find the junction of R16/17." I don't know what "find the junction" means.
 

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On the unmodified ElectroVibe board, R16 and R17 form a voltage divider:

1649915918586.png

On this drawing, their junction is at Vout. On the board, the wiper of your phase trim assembly would connect at this junction.

It sounds like you should just try the stock circuit until you get your “sea legs”.

The Electrovibe really isn’t a beginner project.
 
Yeah, I’m going to skip this mod. The others I am interested in are just component swaps (other than the speed LED thing we talked about earlier today) so I’ll do those. Again, thanks for all your help!
 
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