3xChamp Question

[Anonymous]

Hello everyone,

Newbie to pedal building here. This is my first post, and it’s regarding my first ever successful build: the 3x Champ. obviously I feel great and am proud of my first build, but I do have a question about it.

It sure packs a heck of a punch, as the description in the instructions state. But the description also says you can start from a clean boost, but there’s nothing clean about even the lowest drive or volume settings on the one I built: it ranges from light dirt to pure filthy breakup. Don’t get me wrong, this is awesome, but I wish it would work as a clean boost as well. So my questions are thus:

1. Could how I set my trimmers have an affect on this? I know I installed them correctly, but I had no idea what to do regarding setting them (have never worked with trimmers before), so I just fooled around with the settings until I found the one I thought sounded the best.

2. Could switching transistors affect how clean/dirty it sounds? I used the 2N547, but the instructions suggested possibly experimenting with a J113, MPF102, or J201. How would this affect the sound?

3. And finally, could have I have done something wrong with the build to cause this?

forgive the long post and possible dumb questions. Keep in mind I’m just a beginner :). And to show off my first success, I’m attaching a picture of the finished product.

Thanks in advance for your help!

 

[Chuck]

Ideally you want to bias the 2N5457s to between 4.5v and 6.5v using those trimmers and a multimeter.  You’d power the pedal up and place the multimeter probe on the Drain of each 2N5457 the adjust the trimmer up or down until you get the correct value – the correct value depends on the 2n5457 (generally around 6.0v) and your taste (you could find that 5.9v is the magic tone or 6.2v is way better).  The way the board is laid out the Drain is the leg of the transistor closest to the bottom of the board. You would have to do the same thing if you were using J113s, MPF102s or J201s.

If you don’t have a multimeter you can sort of do this by ear by starting with all three trimmers set close to the same point and slowly tweeking each one up or down the same amount in small increments until you get the sound you want.

Chuck

[Anonymous]

Chuck, you’re an amazing human being.

The process you explained (and explained exceptionally well) is completely new to me and sounds like the answer to my problem.

would I be correct in assuming that a 6.5v setting would produce a slightly dirtier tone than 5.9V (i.e. the higher the Voltage, the louder/heavier/dirtier the tone)?

[Playsforfun]

Welcome Geoffrey. Congrats on the build firing right up. That’s a great feeling. Mine starts as a sweet boost before any breakup. Not sure what is in it for transistors right now but I love it. This quote is on my version of the build doc…

“*If you want a cleaner sounding drive try using an J113 at Q1 and Q2, however for a slightly dirtier sound we recommend the use of a 2N5457 at Q1, Q2 and Q3. This falls under “Socket and See”. Always use sockets.”

So, yes, experiment for differences along with following Chucks advice for bias setting. Among the list of must have’s is a good multimeter. I like having two. 1 is left ready to test caps and the older one set ready for resistance. Let us know how it goes and what you settle on. Cheers.

[Anonymous]

Thanks for the warm welcome and feedback!

Strangely, my document doesn’t say what yours does; mine says, “Feel free to experiment with J113, MPF102 or J201. Socket and see.”

I’ve got a decent multimeter; and with both your and Chuck’s advice, I’m confident I’ll now be able to get sound I’m looking for.

Thanks again and I’ll keep you guys posted.

[Anonymous]

UPDATE: So I switched out the 2N5457s in Q1 and Q2, and left a 2N5457 in Q3 (as @Playsforfun suggested.. I then followed @Chuck’s instructions above and…success! I was able to get all 3 transistors int the 6-6.5v range, solving my lack of a clean boost problem and the pedal sounds great. However, there is one thing I’m curious about regarding these results:
No matter where I set the trimmer, I was only able to get all 3 transistors in this range of 6-6.5v. I thought I would have more range than that to experiment with. Does this signify anything?

Thanks everyone here for your help. I’m sure I’ll be back on here bothering you all again with my next novice issue soon.

[Barry]

It just signifies that there is a great amount of tolerance between transistors.

The important thing is that you have it biased in a good range that works, and sounds great.

[Anonymous]

Thanks, Barry, and I agree; it was almost one of those “Why ask why?” moments, but still being new to this, I want to learn as much as I can.

 

[Author]

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