Question on the Wampler Pinnacle...SOLVED!

[alphadog808]

Hey guys,
  So, I've done the timmy, finishing up a Zendrive, and am looking at doing a Wampler Pinnacle.  I've been looking over the vero layout, but I noticed that there isn't any mention of where to hook up boost 1 and 4 and vint/mod 3?  Do I assume I leave those lugs unconnected?  Doesn't seem right to me, for some reason...

[induction]

Vint/mod and Boost are both double throw switches being used as single throw on/off switches. In other words, anytime you need a DPST or SPST, you can replace it with a DPDT or SPDT and leave some of the lugs disconnected. (In this case, you are correct, boost 1 and 4 and vint/mod 3 are left unconnected.) This seems like a strange practice until you discover that DPST and SPST switches can be hard to find in reasonable sizes and form factors, but DPDT and SPDT switches are widely available.

[alphadog808]

Ok, so I read up a bit more on the pinnacle and it seems many had problems biasing their jfets to get the pedal working.  Seems like a decent stumbling block.

That being said, wouldn't putting in trimmers for each jfet would be a good solution to this?  It seems a few people did so, but only for Q5 and Q6...the 22k resistors associated with them. I'm not sure if that was because those are the only jfets that need trimming?  I'd assume it's possible Q1-Q4 could need trimming as well...if so, which resistors need to be swapped for trimmers?  From reading the posts on the pinnacle I figured out what resistors get swapped on Q5 and Q6.

Is there any downside putting a trimmer in for each jfet?  If not, my *stupid* question is this...haha.  The trimmer has 3 pins, but the resistor on the vero has 2 pins.  What do I do with the 3rd pin on the trimmer?  I am assuming I just use the left and middle pin OR the right and middle on the trim and ignore/cut the extra pin...?  

Is there a recommended trimmer suggested?  I think I read 47k was recommended.

Thanks guys, hope someone can help this n00b!  

[induction]

Brian Wampler suggests selecting J201's that bias correctly with the given resistors, rather than swapping resistors or installing trimpots to dial in the bias. This is because the resistors determine the gain and influence the EQ, and his pedals are designed for a specific gain and EQ. In other words, swapping resistors to bias the J201's will make your pedal sound different from the original.

That being said, you might not care if it's a perfectly accurate clone, as long as it sounds good to you. In that case, the trimmers are a fine idea, though I would certainly breadboard first to be sure.

With the trimmer, you are trying to make a variable resistor. So you can use legs 1 and 2 in place of the resistor leads and leave leg 3 unconnected. Alternatively, using legs 2 and 3, and leaving leg 1 unconnected also works, but reverses the pot rotation.

I wouldn't mess with the resistors on Q1-Q4. Q5 and Q6 are configured as common source amplifiers (similar to so many other Wampler designs), and can be biased by swapping drain resistors, but Q1-Q4 are configured more like AMZ mini-boosters (aka mu-amps). In other words, they are two boost stages that each contain two J201's in a push/pull configuration. They are self-biasing as long as the J201's are reasonably matched in each stage. (Q1 and Q2 should match. Q3 and Q4 should match, but Q1 and Q3 don't have to match, etc.) Unless you are having problems, you shouldn't worry about Q1-Q4 very much, but you can always build the Greatly Improved JFET Matcher II if you want to be positive. Or you can just swap them until the voltages match those from a verified build.

[alphadog808]

Wow, that answers my questions and then some!  Thanks!  I ended up ordering 6 j201s and 2 trimmers.  I'll put sockets on the trimmers so once I get it set right I can put the appropriate resistor in there.  Hopefully the 6 I ordered will match enough!  :)  

[alphadog808]

hey guys,
   so an update, I finished the pinnacle, and it sounds pretty good.  As I never had a real pinnacle, I'm not sure how close it sounds to the real deal.  That being said, I got the voltage measurements from my Q1-Q6 and some of them are close to the real pedal, and some seem further off.  

So...here are my voltages vs what is on the real wampler.  I only have trimmers for Q5 and Q6.  When I first trimmed the pedal, I noticed I was using a 9.6v power supply, I retested the voltages but didn't retrim Q6 yet, as it looks off and I can fix it with the trimmer.

Do you think I'm close enough on Q1-Q4?  If not, anything short of trimmers I can do?

Here's Wampler's...
Drain / Gate
Q1 4.72 / 0
Q2 8.98 / 2.99
Q3 4.78 / 0
Q4 8.98 / 2.99
Q5 3.59 / -1.68
Q6 3.86 / 0


Here's mine.
Drain / Gate
Q1 5.14 /0
Q2 8.94/2.98
Q3 5.06/0
Q4 8.94/2.98
Q5 4.06/.04
Q6 3.35/0

[induction]

Q1-Q5 look fine. You could try tweaking the trimmer on Q6, but let your ear be your guide.

[alphadog808]

Thanks for the response.  I did notice that I think Q6 would cause bass flubbiness if it was off by too much.  I'm not too sure what Q5 did tho, I didn't hear a difference when I changed resistance.  

I do seem to get some pretty big whining when I engage the boost but it's not enclosed yet.  I have the input and output using shielded cables, but I hope that enclosing it and running shorter cabling will remedy this...

[alphadog808]

So I've been doing my pinnacle testing with all the knobs on full.  It seems that I get crazy feedback/whine/squealing when I engage the boost and when I go from vintage to modern.  When going to modern, it sounds really tinny.  I hope it's just the fact that the knobs are all on full.  

That being said, it's not boxed yet an the wires are long, so I'm hoping that's the issue on both.  

However, I was looking online to see if anyone else was able to fix their noise issues on the pinnacle as it seemed pretty common.  I stumbled across this person's layout and was surprised to see that

1) The wiring up of the vintage/modern was different than tagboard
2) The wiring up of the boost was different than tagboard
3) He said he was able to get rid of alot of noise by lowering the resistance of the 1M resistor on the input.  That's basically pulling down impedance, correct?

Here's the guy's schematic

And I guess he modded it more to give make it even more quiet...among other things.


I just wanted to confirm the boost and vintage switch wiring was correct?  And I pray the boxing and shortening of wires gets this more quiet.  It's an AWESOME sounding pedal, but seems much more touchy on the noise...

[alphadog808]

An update...and a solution!!  For me, at least...

I've been focusing so much on correct voltages on the J201s, wirin,  etc that I neglected to let my ears do the work.  I figured out that I could tune Q5 and Q6 to stop squealing.  And as I turned the trimmer the tone changed for the better/worse.  It seems that Q6 is tied to volume.  Once I brought it down to a non squealing level, I could then tweak Q5 to taste.  It is TOTALLY quiet on all settings!  ;D  When I checked the voltages of Q5 and Q6, here's what I got..

Mine:
Q5 - 1.36
Q6 - 8.86

Wampler:
Q5 - 3.59
Q6 - 3.86

So, I guess the fact that the jfets didn't match as well as Wampler's means I had to tweak by ear rather than by their spec.  I think everything is good!!  

Thanks so much for the help guys, I hope this can help someone else in the future.

I don't know if the voltages I'm using is too high or low, but now it's working and man, the boost tone is SWEET.