# Suhr Koko Boost



## equinox (Dec 19, 2022)

I'm opening up a thread on the Suhr Koko Boost as it's been YEARS and a LOT of A-listers use it in their rig, but still, no one is/has been cloning it!!

They have 2 versions...the one in the double-size enclosure and the newer one in the single package.

I had the dual one and worked to reverse it (Koko Boost Rev 3A), but at the time, I was having issues with my soldering iron and temperature sensor and it fried a couple of the components, so was unable to do an 100% accurate trace/reversal!

I can post what I had and left off and hopefully get some traction in getting this thing reversed and a clone unit/PCB created.

There was also some preliminary schematic(s) created by someone else.  I hope this helps.


----------



## equinox (Dec 19, 2022)

Preliminary Schematics


----------



## equinox (Dec 19, 2022)

Preliminary BOM from 2016


----------



## equinox (Dec 19, 2022)

I have many more pictures, but these are the main ones.  
Let me know if anything else is needed.


----------



## spi (Dec 19, 2022)

This is the second time today I saw a circuit that had this arrangement of transistor and diode between stages.  What does this do, and what is it called?  I tried to google it but I'm not finding anything.


----------



## Robert (Dec 19, 2022)

spi said:


> This is the second time today I saw a circuit that had this arrangement of transistor and diode between stages.  What does this do, and what is it called?  I tried to google it but I'm not finding anything.



It's a JFET switch.    Pulling the cathode end of the diode low turns the JFET off.

Take a look at pretty much any Boss or older Maxon/Ibanez schematic and you'll see a similar arrangement for bypass switching.


Does this have the "Hold footswitch for alternate function" trick like some of the other Suhr pedals?


----------



## equinox (Dec 19, 2022)

More photos
I don't think so about any kind of "Holds".  In the pics, you can see the footswitches used and in the BOM I had identified and entered as momentary (normally open)


----------



## Robert (Dec 20, 2022)

Ahh yep, the "Reloaded" version does the Hold trick.

The standard model has switchable buffered/true-bypass, that's likely where the JFET switches come into play.


----------

