Converting the uPOG for True Bypass

[Ch0jin]

A little while ago I bought myself a micro POG and it's a fun bit of gear, especially the sub octave section. It does however have a significant issue in my rig as a result of it's lack of true bypass.

Now before I go on, know that I'm not just a true bypass fanboy who thinks everything needs true bypass just because I heard about it on the intrawebs. I'm not THAT guy.

Anyway, as soon as I inserted it into my pedal chain the issue became very obvious. Specifically, when disengaged, the buffer plays havoc with my germanium fuzz pedals causing pedals before it to sound harsh, and pedals after it to sound thin and just generally nasty. For the most expensive pedal I've ever bought, this just would not do, no sir.

So I had a look on the web for a TB mod and whilst one vendor offers the conversion at time of purchase for $40 (a very reasonable labour cost), I could not find a single person who knew how to do it other than the oft quoted "build a loop switch and put it in that loop" kind of response. That's a crap solution IMHO and I knew I could do better, so out came the pen and paper and the multimeter and after some circuit tracing I nailed it.

So here we go, exclusive to thefret.net and perhaps for the first time on the intrawebs I give you...

Modifying the microPOG for true bypass.

For some reason the uPOG uses a 3PDT stomp switch with one whole pole not connected to anything! I'm assuming they (new sensor/EH) buy 3PDT's in bulk so using a 2PDT would actually be more expensive for them, but for hackers like me, it's fantastic news because it means apart from 20cm of wire and some solder, the mod costs nothing but time.

Step 1. Strip the unit being very careful removing the knobs. They are very tight and being patient and gentle will help avoid scratching the label, or worse, damaging the internals of the pots.

You will see the stomp switch has a nice little PCB and an eight connector ribbon cable joining switch to the main PCB.

Note: At this point you might notice all the pins of the switch are soldered and there are PCB traces for all pins leading to the ribbon cable. If you look closely at the main PCB though, you'll see that pins 2,3 and 4 actually go nowhere once they have hit the main PCB. This means that the whole left hand side of the switch (one pole) does nothing.

Step 2. Remove the switch PCB from the switch and then remove the ribbon cable from the main PCB. The switch PCB is easy, just heat and suck. The ribbon cable is a lot more fiddly and you will likely need a sucker and braid, especially on pin 5 which is ground. Once you have removed the switch PCB and ribbon cable, examine the area on the main PCB where the ribbon cable was to make sure there are no stray pieces of wire left over from the cable removal. I had to clean up quite a few.

Here it is removed.




Step 3. Flip the main PCB over and locate the hot (signal) pin of the input jack. You'll need to solder a wire on here to run to the switch.



Step 4. Solder short sections of wire into pins 1, 5, 6 and 7 of 'CN1B' where you removed the ribbon cable.

Step 5. Solder a short jumper of wire between the bottom left pin and bottom right pin of the foot switch.

Step 6. Drop the main PCB back in place in the case and fit the foot switch to the case. Bolting the foot switch back to the case makes soldering the wires on easier in my opinion.

Step 7. Solder the wire you ran from the underside of the main PCB to the pin labelled "IN" and the other four wires are attached as per the pic below noting that pin 1 should bridge two pins of the switch as shown.



Step 9. Test, reassemble and rock on!

What you now have is a True Bypass pedal with the following improvements.

a. When the pedal is disengaged it does NOT mess with Ge fuzz pedals, or anything else for that matter.

b. You still get sound if the pedal loses power and is disengaged.

c. Dry output now passes dry signal regardless of the state, or power of the pedal.

d. What I have done here is left the the buffer completely in tact when the effect is engaged so there should be absolutely NO change to the way the pedal works when it's engaged.

Why EHX didn't just do this in the first place is beyond me, but at least if anyone needs the info the groundwork has been done.


Lastly, I did consider that as there is no info on how to do this that I could find, that I should write up the details in a PDF and try and flog them on eBay for profit, but I've learned so much from thefret I thought I'd just drop the knowledge here and maybe, just maybe, it'll drive some extra traffic to the site which I assume helps Robert pay for it????

Anyway, questions, comments, etc welcome.