Monday, August 21, 2017
JHS Charlie Brown V3
Unrelated to the Angry Charlie circuit, the Charlie Brown emulates the brown sound of a JTM45 amp and is a variation on the zVex Box of Rock without the boost section. The input stage is an AMZ Mosfet Booster (replacing the SHO input stage of the Box of Rock to avoid crackle in the gain pot), and the tone control has been modified to include the AMZ presence control.
Nice pedal !! i will build it very soon.. I'd always thought BSIAB was an Charlie Brown, do you have the link to the schematic?
ReplyDeleteSearch over on FSB.
DeleteJust finished this morning but unfortunately there is no signal passing through. Checked for solder bridges but found none. Will check again once I get home from work.
ReplyDeleteIs there a way to upload photos in the comments?
DeleteYou can post links to photos hosted elsewhere, but you can't embed them.
DeleteOk cool... I got it working but it really gated. Tone control works and it get even more gated when I turn up the gain pot. When it's all the way down the signal gets through easier. Is the 9.1v zener diode clipping the signal too much? Or mis biased fets? Think I'm going to try 2n5457s and j201s and see what happens. If anybody has any ideas let me know thanks. I can give voltage reading if need be.
DeleteThe zener is there to protect Q1. It's not clipping anything. I would try adjusting the values of the resistors going to the drains from the voltage rail. I wouldn't try subbing the MOSFETs for JFETs. You could sub 2N7000s for the BS170s. Just rotate them 180º.
DeleteOk thanks😀. I'll put some sockets in for those resistors and give it a go. I also noticed on the gut shot that's floating around on fsb that there are three 22n box caps on the board. Wish I could see the trace side... I'll let you guys know what I figure out in a few.
DeleteYou can mark it!! Got it working!! Had a cold joint on one of the drains of the bs170. Sounds good too!! Thanks for the layout man!!!
DeleteCool! Glad you got it working.
DeleteOnly thing is the presence pot... Think it has anything to do with the 22n in the gut shot pic?
DeleteCheck this mods for the BSIAB circuit, it uses the same tone control, i think #2 is the one on this pedal... http://postimg.org/image/qz49x137n/
DeleteThe schematic of the pedal hasnt really been verified, it's based solely on gut shots (see the FSB thread).
DeleteThe presence pot is a mystery to me, I think we must have missed something, or the pot must be a much higher value, cause as is, it cannot make a difference.
Of course you can try various tonestack values, and find the ones you prefer. But we dont know for sure what values the Charlie Brown uses.
One thing seems sure to me: the 100n going to Tone3 should be 10n.
Also... the 1nf (input cap) should be 100nf, and the 100nf on the left going to 470k/470pf should be 22nf.
DeleteAgain, careful, the schematic posted on FSB isnt accurate.
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ReplyDeleteThe schematics have not been verified. I posted myself a few message on FSB, based on what I could guess from the gutshots. But the contour pot value isn't verified.
ReplyDeleteAnd I feel pretty sure the 100n going to tone 3 should be 10n.
The contour pot always seemed odd to me.
Anyways, I don't think you should totally trust the schematics posted on FSB.
Also... the 1nf (input cap) should be 100nf, and the 100nf on the left going to 470k/470pf should be 22nf.
DeleteAgain, careful, the schematic posted on FSB isnt accurate.
Just thought I'd share in case it is helpful to someone - I was able to get a useful Presence control by replacing the 82k resistor with something between 3-8k. Not sure what the CB actually has in there, but I'm using a 5k6 currently and it works well. Figured this out after comparing the tone circuit in the layout to the AMZ Presence Control (http://www.muzique.com/images/tone2c.gif).
DeleteAnd what about Gain pot? Do anything, but after 3/4 made evil gain. Maybe must be C characteristic?
ReplyDeleteSame thing here. Have you ever figure that out?
DeleteI'm thinking of trying a C5k pot, but I do not have it handy at the moment.
Good Nigh, one question This project is working well?...I built It, but didn't work, Maybelline i did something wrong here, i'll be wait for coments...thanks
ReplyDeleteYes, it´s working fine. Just built two this weekend. The first worked in the first attempt, but I had problems with the second. Nothing serious, mauybe a bad weld. Really cool distortion, much better than my Boss DS2.
Deletecan i replace 10M Ohm resistor with 20M ?
ReplyDeleteUse two 20M resistors in parallel and you'll have 10M of resistance.
DeleteIs it really verified? I checked at least 5 times and it still not working :(
ReplyDeleteI built this one and it works, except the presence control.
ReplyDeleteSomeone had the same problem?
I'll try to change components mentioned on comments above.
Did you have success changing components to make the presence control work?
DeleteHello!! Nice job on this one!!
ReplyDeleteI am just facing an issue with presence control.. it doesn't seem to chance anything.
Dear all, the presence control will not work as Charlie Brown v.03 on this way...
ReplyDeletePlease, look at the FSB discussion https://www.freestompboxes.org/viewtopic.php?t=14501&start=40