Author Topic: Green Mujina  (Read 6816 times)

stonerbox

Re: Green Mujina
« Reply #60 on: January 15, 2018, 01:02:53 PM »
So what was the problem? You removed the last op amp section?

Why 500k volume resistor, 50k will do the job too.

That Volume potentiometer is already swapped. Everything will make sense as soon as I post the 1.20v schematic. Hold on!
"JFETs are like people.... similar,  but different from one another."
- BubbaFet

stonerbox

Re: Green Mujina
« Reply #61 on: January 15, 2018, 02:57:31 PM »
I have highlighted all that needs modification.. brand new pedal but with the character from the old one intact and all the controls are 100% more responsive. Goddamn love it. Sooner or later there will be a final schematic but not just yet.
[click image to enlarge]


1.20v Updates

1. Adjusted the two smallest capacitors in PAW SIZE.
2. Swapped out the VOLUME 1 potentiometer from 50k > 20k (Maximum is 25-30k or the circuit will start to oscillate again!)
3. Lowered C6 from 6.8uF > 1uF.
4. Removed R19.
5. Reconfigured connections in the final opamp stage (HPF) and added 1M with 1/2VCC to + pin 3.
6. Added a Low Pass Filter on the Master Volume
7. Swapped the Master Volume from 500k A > 250k A + 47k from wiper to lug 1 (for smoother control).
« Last Edit: January 15, 2018, 03:58:29 PM by stonerbox »
"JFETs are like people.... similar,  but different from one another."
- BubbaFet

duck_arse

Re: Green Mujina
« Reply #62 on: January 16, 2018, 08:35:14 AM »
I think you still need something at R19, to work against the 22k. if you put 22k to V/2 from (-) pin, it should do gain of 1+1, non inverting. I think.

I think the mater volume pot is not drawn quite right - it will pull the nameitt 1k to ground when full ccw.
put the coffee down, Antonis, and nobody will get hurt.

"How many fingers am I holding up?"

stonerbox

Re: Green Mujina
« Reply #63 on: January 17, 2018, 09:06:32 AM »


Raw signal from microphones (Mouse and C414) with no EQ except for HPF & LPF.

Signal chain
Sloppy Playing
70s Les Paul Standard
Fender Black Face clone head - had plans to use my Laney Pro Tube but apparently s/he is not in a healthy stage of life right now..
No name cab with Celestion GK-12 100w
MICS
DAW
LOW PASS 100Hz / HIGH PASS 10kHz.
« Last Edit: January 17, 2018, 09:55:04 AM by stonerbox »
"JFETs are like people.... similar,  but different from one another."
- BubbaFet

stonerbox

Re: Green Mujina
« Reply #64 on: January 17, 2018, 11:08:37 AM »
Just realize the video looks a lot like the movie Excalibur (1981). I was both intrigued and somewhat afraid of that movie as a youngster.

« Last Edit: January 17, 2018, 01:20:03 PM by stonerbox »
"JFETs are like people.... similar,  but different from one another."
- BubbaFet

stonerbox

Re: Green Mujina
« Reply #65 on: May 17, 2018, 05:34:41 PM »
Ok, so I'm returning to this project after several months of caring for our little bratty Shiba Inu pup. ;)

I have got several requests to merge the final schematic with the layout but I want to adjust somethings first.
The constant noise that lives in or around Q3 needs to be dealt with somehow. Before Q3 the signal is completely noiseless so something is going on there. It uses a J113 and some of them are pretty noisy compared to J201 if I remember it correctly. I could test another J113 and see if it helps.

Can you guys spot anything else that seems strange around Q3? I know that the EQ values are somewhat unorthodox, could it be something to look into? Thanks.



« Last Edit: May 17, 2018, 06:30:02 PM by stonerbox »
"JFETs are like people.... similar,  but different from one another."
- BubbaFet

stonerbox

Re: Green Mujina
« Reply #66 on: May 18, 2018, 05:14:34 AM »
I tried swapping the J113 for a J201 at Q3 and the noise and pops goes down significantly but is still present. Could the circuit need more filtering upfront of Q3?

Here's a sample. First J113 then the J201. Bunch of low noise, cracks and pops. Preamp volume 1 set at 0 to isolate the noise. I have also boosted the recording with about 10db so you can clearly hear the character of the noise.
http://tropicalhippo.com/GreenMujina/noise.wav
« Last Edit: May 18, 2018, 08:54:08 AM by stonerbox »
"JFETs are like people.... similar,  but different from one another."
- BubbaFet

EBK

Re: Green Mujina
« Reply #67 on: May 18, 2018, 05:43:25 AM »
Could you post a pic or two of the build?
No affiliations. If I glowingly mention specific merchants or products, it is because I like them without having to be paid to like them.

stonerbox

Re: Green Mujina
« Reply #68 on: May 18, 2018, 08:32:38 AM »
Could you post a pic or two of the build?

Wow, Imgur killed the quality. I'll reupload them somewhere else...




Edit: Done.

« Last Edit: May 18, 2018, 08:48:28 AM by stonerbox »
"JFETs are like people.... similar,  but different from one another."
- BubbaFet

EBK

Re: Green Mujina
« Reply #69 on: May 18, 2018, 08:58:54 AM »
Woah!  Didn't quite expect something like that!
I'm going to assume for the time being that everything far away from Q3 is fine -- even thise two tantalum caps with one lead hanging in the air like they are about to give each other a high five.  :icon_razz:

The negative lead of C13 looks broken in the one pic....

Some of the solder joints look suspiciously clumpy....

Still looking around to see if I spot anything else.
« Last Edit: May 18, 2018, 09:02:46 AM by EBK »
No affiliations. If I glowingly mention specific merchants or products, it is because I like them without having to be paid to like them.

stonerbox

Re: Green Mujina
« Reply #70 on: May 18, 2018, 09:06:24 AM »
Woah!  Didn't quite expect something like that!
I'm going to assume for the time being that everything far away from Q3 is fine -- even thise two tantalum caps with one lead hanging in the air like they are about to give each other a high five.  :icon_razz:

The negative lead of C13 looks broken in the one pic....

Some of the solder joints look suspiciously clumpy....

Still looking around to see if I spot anything else.

It's a real slobber I know but it works perfect except for the noise. The two tantalum caps (C3) is disconnected for now. Don't want any interference with the Paw switch ( cap ) values. C13 is believe it or not actually connected so no worries there and I am about to clean up the big blob of solder on the ground (black) cable in left center. The two loose resistors (R19) to the far right is also removed now. Same thing goes for the tiny thing sticking up from top right Opamp, used it as connection testing earlier.
« Last Edit: May 18, 2018, 09:13:39 AM by stonerbox »
"JFETs are like people.... similar,  but different from one another."
- BubbaFet

EBK

Re: Green Mujina
« Reply #71 on: May 18, 2018, 09:13:15 AM »
I'd really recommend using something non-conductive (maybe a chopstick or bamboo skewer) to gently poke the various component leads around Q3 to see if you can make it pop.  A cold or cracked solder joint somewhere is my suspicion.
No affiliations. If I glowingly mention specific merchants or products, it is because I like them without having to be paid to like them.

stonerbox

Re: Green Mujina
« Reply #72 on: May 18, 2018, 11:21:44 AM »
I'd really recommend using something non-conductive (maybe a chopstick or bamboo skewer) to gently poke the various component leads around Q3 to see if you can make it pop.  A cold or cracked solder joint somewhere is my suspicion.

I poked around and found nothing other than that Q1 is slightly microphonic (SMD J201). Then it happened... I accidentally touched the metal top of C11 and the noise stopped! I tried touching all the other electrolytic caps too but the noise only stops by touching either C6 or C11. What does this mean?
« Last Edit: May 18, 2018, 11:26:34 AM by stonerbox »
"JFETs are like people.... similar,  but different from one another."
- BubbaFet

EBK

Re: Green Mujina
« Reply #73 on: May 18, 2018, 11:43:52 AM »
You could try resoldering C11.  Maybe replace it. 

What is that resistor hanging off the end of it.  That's not on the schematic, right?
No affiliations. If I glowingly mention specific merchants or products, it is because I like them without having to be paid to like them.

stonerbox

Re: Green Mujina
« Reply #74 on: May 18, 2018, 12:03:36 PM »
You could try resoldering C11.  Maybe replace it. 

What is that resistor hanging off the end of it.  That's not on the schematic, right?

To be quite honest I don't really recall putting the resistor there.. it's a 120k and must be there to limit the saturation of Q3... and no, it is not present in the schematic or layout.
« Last Edit: May 18, 2018, 01:57:02 PM by stonerbox »
"JFETs are like people.... similar,  but different from one another."
- BubbaFet