A few Son of Ben questions/tips (J201 orientation, biasing, optional cap, etc)

Joben Magooch

Well-known member
Hi all, just a few (hopefully) quick questions for the Son of Ben.

1. Can anyone confirm to me the correct pinout/orientation of J201 mini-PCBs? I ordered a few from Aion. It looks like the proper orientation (assuming the power, I/O, etc is facing up/north) is for the J201s to go D/S/G (L-R). Maybe a silly question, but would there be any reason why you couldn't flip the mini-PCB 180 degrees end-over-end so that the component is facing down ('white' side up) so long as D/S/G are still aligned correctly? Or would it make more sense to keep the component facing up and bend/angle the header pins so the trimpots aren't obstructed? Hopefully my pictures make it clear enough, lighting was kind of crummy.

2. Build docs mention that C10 (10u electro) is optional and was only used in the first ~100 units. First off: any pros/cons to keeping/omitting it? Just a bit curious as to what it is doing (or not!). Second: If omitting, should the C10 pads be jumpered?

3. I've never done any builds that required biasing any components before. I thought there was a thread on how to bias this one but I've not been able to find it... per the schematic it says "adjust trim 2/3 for 4.0v on drain of Q2/Q3". So just kind of walking through it/thinking out loud: get everything assembled, give the pedal power...set multimeter to volts DC, then probe red to drain and black to ground and adjust trimmer until it reads ~4.0v? That seems fairly straightforward to me (unless I've missed something), but for Q1 it says "adjust to 2k ohm" - how would I go about doing that part?
 

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1. You have them oriented correctly in your pic. A clue is to look at the SMD pads. Note where the Drain leg of the SMD pad is connected to the "D" hole of the through hole. Google is your friend, look up data sheets and pinouts before committing.

2. No need to jumper if omitting C10. I put mine in. I'm not sure it makes any significant or appreciable difference in sound with it in or out but there are a few threads on the subject. Forum Search is your friend :) ....look up "Son of Ben" or "Benson".

3. A a rule of thumb you want to bias by measuring the voltage with the pedal engaged at the "Drain" leg of the JFET. In the case of this board, you can actually use the SMD pad for "D" as a measure pad to put your positive DMM lead. As a VERY GENERAL rule of thumb you want to start with 1/2 of input VDC. So if you measure say 9.6v at the voltage input pads of your board then shoot for 4.8v at the drain leg. Then fine tune by ear to what sounds best to you. Some circuits have specific biasing ratio's like the Benson which calls for 4.0v. So when the bias voltage is called out (not too common) then shoot for that and then fine tune by ear.

It's an awesome pedal. Here's my demo of my build.

 
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