DIYstompboxes.com

Hi,

I've spent the last three days working on this. I got intrigued by the legendary GT120/O Green Matamp and started a conversion of the preamp but in the end it transformed into something of its own. I added a few things myself and some that I stole (soft MOSFET clipping from Jon Patton's "Snow Day" overdrive).
It goes from overdrive to loud and crushing. The EQ (Bass, Treble, Boost) - Grain - Volume 2 interacts with each other in interesting ways. There are a lot of different sounds that can be dialed in here. I fairy new to all of this so if anyone of you have improvements in mind feel free to share them. It's meant to push a tube amp and that is what it does in the clips below.

I call it Green Mujina - Mujina generally meaning badger in a Japanese.

Full sized schematic: tropicalhippo.com/GreenMujina/Green-Mujina-Full-size.png (http://tropicalhippo.com/GreenMujina/Green-Mujina-Full-size.png)

(http://tropicalhippo.com/GreenMujina/Green-Mujina-preview.png)

Demonstrations (breadboard):

Preamp only:
tropicalhippo.com/GreenMujina/Green%20Mujina%20Preamp.wav (http://tropicalhippo.com/GreenMujina/Green%20Mujina%20Preamp.wav)
Preamp + Power Stage:
tropicalhippo.com/GreenMujina/Green%20Mujina%20Power%20Stage.wav (http://tropicalhippo.com/GreenMujina/Green%20Mujina%20Power%20Stage.wav)
EQ and Grain interaction:
tropicalhippo.com/GreenMujina/Green%20Mujina%20Power%20Stage%20EQ%20-%20Grain%20interaction.wav (http://tropicalhippo.com/GreenMujina/Green%20Mujina%20Power%20Stage%20EQ%20-%20Grain%20interaction.wav)

Ben

You are new to this? This is amazing for a start! I have only one comment in the preamp only sample - there seems to be some gating. The tail end of the notes seem chopped early. Now this can be a plus if you want it.
I like how it can get crazy with the Grain changes.

Quote from: aron on April 05, 2017, 04:34:00 PM
You are new to this? This is amazing for a start! I have only one comment in the preamp only sample - there seems to be some gating. The tail end of the notes seem chopped early. Now this can be a plus if you want it.
I like how it can get crazy with the Grain changes.

I have been at it for a couple of years but I don't really know anything, never studied electronics. Trial and error been my school. I will have to check the gating on the preamp, thanks.

Dude, that thing's friggin brutal  :icon_twisted:  Do you have a layout designed yet? What amp are you playing through in the clips?

I used a Fender 65 Blackface clone. Never done any layouts before but I will start to work on a vero very soon!

Schematic update. Labeled all the components in order and I also moved the first dual gang potentionmeter connection. In the previous version it was connected in between C13 and C14, which is incorrect.

Full sized schematic: tropicalhippo.com/GreenMujina/Green-Mujina-Full-size-1.1v.png (http://tropicalhippo.com/GreenMujina/Green-Mujina-Full-size-1.1v.png)

(http://tropicalhippo.com/GreenMujina/Green-Mujina-preview-1.1v.png)

The first demos where over the top high gain, so for balance sake I added some clean ones too.

Preamp + Power Stage with Grain at 0, Vol 1 at 0, Vol 2 at 10 and guitar volume on lowish (around 2-3). On clip 2 I boosted the volume of the guitar to get more overdrive.

Clean:
tropicalhippo.com/GreenMujina/Green%20Mujina%20-%20Clean.wav (http://tropicalhippo.com/GreenMujina/Green%20Mujina%20-%20Clean.wav)

Dirtier:
tropicalhippo.com/GreenMujina/Green%20Mujina%20-%20Dirtier.wav (http://tropicalhippo.com/GreenMujina/Green%20Mujina%20-%20Dirtier.wav)

The C13-C14 connection makes no sense.

Quote from: bool on April 06, 2017, 10:34:35 AM
The C13-C14 connection makes no sense.

That's right, C13-C14 does not make sense. In the latest version of the schematic I've removed C13 since it has no purpose. It was a leftover from an earlier breadboard draft.

C3 also appears redundant. might be better to have C4 hard wired, and switch C5 (of reduced value) in parallel.

That's a good idea. From the beginning I wanted to do a 3-way system but had none at home. Maybe I'll do two caps as you mentioned or a potentiometer for seamless adjustments or a rotary switch for a great deal of caps. We'll see.

I've rewired the Volume 1 to ground (via a 1k resistor) instead of straight to the next stage. This makes it a breeze to dial in cleaner sounds.

Updated schematic and my very first go at creating a layout. It's still unverified.

Schematic (1.2v) changes:
1. Fixed several typos in schematic.
2. Removed the input cap toggle switch for simplicity. This pedal really don't need any more knobs or switches.
3. Removed C13 since it was a left over from past version of the circuit.
4. Reconfigured Volume 1 in a more effective way in order to gain more control over the distortion.

[Click images for full size]
(http://tropicalhippo.com/GreenMujina/Green-Mujina-Full-size-1.2v.png)
(http://tropicalhippo.com/GreenMujina/Green-Mujina-Vero-Layout-%28v1.2%29.png)

Followin' intently :)

Sounds great already.

I built the vero and encountered something strange. I bias all the J201 to 1/2 the Vcc and everything works fine right up to Q3. When Q3s drain sees half the supply no signal goes through it but if I drop the bias down to 1/3 of the Vcc I get signal but at a considerately weaker volume than from the previous stage. Could this information give a indication of what could be wrong? I thought to myself that there probably was an error in the vero or maybe there was a solder bridge somewhere so I built the Q3 stage separately on breadboard but the results were the same.

1.3v of vero and schematic.
(http://tropicalhippo.com/GreenMujina/Green-Mujina-Full-size-1.3v.png)
(http://tropicalhippo.com/GreenMujina/Green-Mujina-Vero-Layout-%28v1.3%29.png)

I noticed that some of your JFET gain stages (Q3 and Q5) do not have a large value resistor from the gate to ground to keep the gate biased at 0V (check out the gate voltages with your multimeter to confirm - are they near 0V?).  This is necessary for the stage to work properly as a common source JFET configuration (see below).  In the case of Q3, you may need to put a cap in front of a 1 meg or so resistor from gate to ground, so as to isolate it from your Grain filter.

(http://electronics.indianetzone.com/images/electronics_039.jpg)

Thanks Frank!

I've noticed that the Grain filter does not have the same effect now as it did on breadboard, it was probably  wired inaccurately. I remember being able to dial the high pass all the way up without the signal being cut and that would be impossible the way it is shown in the schematic.

Given that the HPF was wired differently then I thought it could have acted as a substitute for that resistor you suggest, maybe.

You definitely want to isolate those JFET gain stages with coupling caps so as to keep them from interacting with the other parts of your circuit.  Experiment with cap values to see what sounds best.  Good luck - looks like a cool design.  And don't feel bad about having to rebuild the effect - I have an overdrive circuit that I'd been tweaking (after "perfecting" it on the breadboard) and ultimately rebuilt it on vero three times because I changed something at the last minute!   :P

Wish it did not take so long in between updates but here we go, here is a big one. I have been experimenting and refining this pedal a whole lot the past weeks and something great and powerfull seems to grow out of it. The tone stack has gotten a major overhaul with improved response in cut and boost range. The treble does this peculiar thing where it creates a nice push at 800 Hz - 4 Khz  when the potentiometer is set above 50% and at the final 10% it adds a shelf boost around 4-5Khz (see graph down below). I have also finished the design for a bb1590 enclosure.

(http://tropicalhippo.com/GreenMujina/Design-Green-Mujina.png)

1.7 update/changes:
1. Added a rotary switch with 7 different film and ceramic capacitors after Q1. Range 1uF - 50pF. [Paw Size]
2. Reduced the amount of distortion significantly for string definition and added dynamics. It's gone from over the top to a gravely warm texture.
3. Redone the tone stack completely.
4. Removed the BS170 soft clipping part from Q4 (originates from Midfairways Snow Day OD).
5. Updated the Grain to an active HPF with buffer.
6. Changed Vol 1 from 1M to 500k and R5 to 1K
7. Changed Vol 2 from 1M to a dual 1k and R17 to 250 ohm.
8. Added a passive LPF on Vol 2 (dual 1k). To make a slightly smoother top end when volume/gain is full.
9. Moved Q3 stage from Power Amp section to the Preamp section to balance the output of both channels.

Full sized version of schematic: http://tropicalhippo.com/GreenMujina/Green-Mujina-Full-size-1.7v.png (http://tropicalhippo.com/GreenMujina/Green-Mujina-Full-size-1.7v.png)
(http://tropicalhippo.com/GreenMujina/Green-Mujina-Full-size-1.7v.png)

Tone stack response:
(http://tropicalhippo.com/GreenMujina/Tone-Stack--Treble-Responses.png)
[Click for full size]
(http://tropicalhippo.com/GreenMujina/Tone-Stack--Bass-Responses.png)

I need your guys help again. I been really struggling to get the active filter (Grain) part to work properly. I have been reading up on single supply buffers and filters but I feel like I am stuck. The buffer works but all the types of filters (1 pole and 2nd pole) I have tried have all failed to do what I hope. They either cut the signal (or makes it sputter) at full effect or nothing at all.
For this last version I combined this buffer and this active 1 pole HPF. What am I not seeing here? I have also tried the two different active high pass filters in TI's "Single supply Op Amps Collection". Page 14, 3.1.2 High Pass Filter Circuits. http://electro.uv.es/asignaturas/ea2/archivos/sloa058.pdf (http://electro.uv.es/asignaturas/ea2/archivos/sloa058.pdf)
At the end of the day I am not sure a high pass filter will make the texture that I am hearing in my head I got to try it before moving on.

Current buffer: http://stompville.co.uk/wp-content/uploads/2013/06/149SV.png (http://stompville.co.uk/wp-content/uploads/2013/06/149SV.png)
Current HPF: http://www.ekswai.com/en_highpass.htm (http://www.ekswai.com/en_highpass.htm)

HPF values:
R1= 22k pot + 630 ohm
R2= 22k pot + 630 ohm
R3 & R4 = 330K (V divider)
C1= 330nf

Cutoff = 21-765 Hz

Surely someone got to have some sort of input or ideas about this? No?

How is the progress? I have been following this thread since day one as I'm on the road for a similar pedal. Sadly I don't have any solution for the latest problem.

I been away for a long time and in the meanwhile this baby badger has entered its adult stage of life.  ;)

Been thinking long and hard about how I want the pedal to behave and at the end of the day sound, and I am fairly positive that I have finally nailed it.

It can do bubbly, fat high gain but also crunchy dynamic saturation. It has been a constant balance to never let it get too flabby, dull or flat but never too sharp & stingy either. I am no fan what so ever of that raw eighties high gain. I strive for great mid range with warmth

Alright, enough of my unimportant rambling, let see what has been changed and added. I will post video/sound samples soon and a brand new layout next week (asap everything is figured out).

0.9v Updates:
1. I rolled back the version of the schematic from 1.7 > 0.9. My thought process was greatly flawed, something can't be over 1.0 until it is a fully functional final version.
2. The Grain is totally reconfigured. It is now a wide parametric band boost with sweepable frequency range. It boost frequencies so that the character of the saturation in Q4 and Q5 alters greatly. It ranges from deep bass up to the mid range (around 700-900Hz).
3. Several gain stage adjustments in order to not over do the saturation, there are however still plenty of it.
4. Swapped Volume 1 from 100K > 50k. Both to limit saturation and increase the fine tuning and smooth out the curve from semi clean > crunch > high gain.
5. Lowered the values of several coupling capacitors greatly to avoid an inferno of bass. No dreary and dull mud shall pass in this build.
6. Added a high self pass filter near the end of the circuit to revitalize the high end. Pushes from and above 4,2Khz if my calculation is correct? 1/(2*PI*R32*C25).

Full sized version of schematic: http://tropicalhippo.com/GreenMujina/Green-Mujina-Full-size-0.9v.jpg (http://tropicalhippo.com/GreenMujina/Green-Mujina-Full-size-0.9v.jpg)
(http://tropicalhippo.com/GreenMujina/Green-Mujina-Full-size-0.9v.jpg)

Tone stack response:
(http://tropicalhippo.com/GreenMujina/Tone-Stack--Treble-Responses.png)
[Click for full size]
(http://tropicalhippo.com/GreenMujina/Tone-Stack--Bass-Responses.png)

Help
I would like to optimize and standardize many resistors values. R22-24 could perhaps be recalculated to only two resistors? But how? And if I would change R2 to more common value and make it into a voltage divider how would I do that and still keep the same impedance? I don't want to alter the sound. When the voltage divider is figured out I'll swap C1 so the low pass stays at 10Khz.

Maybe the last two opamps could be merged into one?

Perhaps some coupling caps could be removed too, C18 and C26 maybe? Educate me! :D

One more thing. Thank you QuietRob, Richard and ElectricDruid for helping me with the oscillating Wien bridge /parametric filter in that other thread.

Quote from: stonerbox on July 07, 2017, 06:30:56 PM
Help
I would like to optimize and standardize many resistors values. R22-24 could perhaps be recalculated to only two resistors? But how? And if I would change R2 to more common value and make it into a voltage divider how would I do that and still keep the same impedance? I don't want to alter the sound. When the voltage divider is figured out I'll swap C1 so the low pass stays at 10Khz.

Maybe the last two opamps could be merged into one?

Perhaps some coupling caps could be removed too, C18 and C26 maybe? Educate me! :D

Maybe it got buried in the wall of text so I'll echo it.

Yes, I'm not clear on the purpose for R24 -- it would seem to drop a lot of signal to ground.

Yes it does!  ;D Without R24 or with a lager value the parametric band circuit (on breadboard=long alligator cables left and right) starts to oscillate badly.

R2:

This might work, if your supplier stocks it:


http://www.mouser.com/ProductDetail/Xicon/270-715K-RC/?qs=sGAEpiMZZMsPqMdJzcrNwnK90ix8JRCrrDvXfvOeEX4%3d

My explanation of R2 was perhaps a bit flimsy. I was hoping that some kind of calculation could be used convert the large and clumpsy resistor value (713k) into a voltage divider that would present the same resistance. Is there a calculation for this?

Simple answer, if you have a divider with two resistors, each resistor will drop a voltage proportional to its value, in a simple ratio. That helps to determine the voltage at the junction of the two resistors. The total voltage drop will be the same. You simply need to find the right voltage you want at the split, then make a simple ratio for the drops and the resistor values.

If you had a string of ten resistors with +10V at one end and 0V at ground, each resistor would drop one volt, and you would have a "ladder" with 1V steps.

Excellent Rob, thank you! So I simply measure the voltage drop over R2 then calculate and implement a voltage divider with the same drop and then adjust C1 so the low pass stays at 10Khz. Too easy! I should have solved this one on my own but I got lazy and was uncertain if the conversion to a voltage divider would alter something in the loading of the input signal.

By the way guys, are my schematics too big for your screens? I am on a 4K monitor (3840x2160) but I am trying to keep the sizes manageable for smaller monitors too.

I'm enjoying them on a 1920 by 1080.  :icon_wink:
The green color makes me think of engineering paper.

Quote from: EBK on July 09, 2017, 07:09:29 AM
I'm enjoying them on a 1920 by 1080.  :icon_wink:
The green color makes me think of engineering paper.

That is great to hear! I never really seen engineering paper in real life but I thought the color would match this project. Good to hit some nostalgia though!

I'm having a problem with your preamp/power stage switch. OPA2134A is floating when the switch as drawn. I'd reverse that pole to have common to the opamp, and the empty switch postion taken to V/2, as that stage has no bias when bypassed. C24//C13 appear to be in series, so one of them is backwards. also, I think one is redundant, it might become clearer when the switch is reconfiggered.

R10//R11//R12 - R12 is swamped by the value of R11, so can be deleted. if you multiply the value of those 10k resistors by 10? 22?, you can then reduce the C11 by the same factor. [I think this is how those filter things work.] R6 is also swamped by the 1k and pot, it can be deleted.

I think: R22,23,24,25 and C17, 18 can be replaced by a single cap and two resistors. work out your filter resistor value for say 100nF cap, then split that value to suit your divider and take the gate from there. probably the same goes for that whole "VOL 2" section from C20 to C22.

why 713k at R2? if that is a 20kHz filter with 10pF, there is no usable difference between 713k and 680k. (most might rescale for 68k and 100pF, or as high as 220pF even.)

hard wire the 50pF across the rotary switch, and add the others in parallel. you'll always have a failsafe setting, not reliant on the switch.

master volume is drawn wrong, you want the tip-out from the wiper. I'm a bit hazy on the wiring of the OPA2134 at the end, but will leave comment to the less opamp hazy among us. I hope some of this is correct, and helps.

Good grief, so many mistakes! I am glad someone came along and shed some light on them. I really like your Pre/Pow switch idea.

That Master Volume is indeed miswired in the schematic. I am afraid it is a case of the copy/paste mishap from Vol 2. ;D
I had already removed R11 & R12 in order to keep the signal strong enough when the rotary switch is set at 50pF. I did have my suspicions about the redundancy of R12 & R13 though but I never got to the point of investigating and optimizing these areas just yet. At the moment I am trying to re-bias the preamp section so it will not fizz and buzz when dialing in cleaner sounds. Aron noticed it (in the samples) back when I started the thread but I never got it properly dealt with. No matter how I lower the voltage (pot to ground) in between Q1-Q2 or Q2-Q3 the fizz is still there. Could it be an link to the very small caps in the rotary? I just noticed the fizz/buzz appears when set on the lower value ones (150-100-50pF). EDIT: Never mind it is the same with the larger ones.

Here is a sample of the fizz and buzz. http://tropicalhippo.com/GreenMujina/clean.wav (http://tropicalhippo.com/GreenMujina/clean.wav)

I'll look into all the things you pointed out for me. Also, it is a good idea to keep one capacitor in parallel by the rotary switch even though it would result in 100pF as the lowest value on the switch, right? I do not know if these switches are fragile but if it breaks we got a backup plan. Thanks!

Quote from: duck_arse on July 09, 2017, 11:32:18 AM
why 713k at R2? if that is a 20kHz filter with 10pF, there is no usable difference between 713k and 680k. (most might rescale for 68k and 100pF, or as high as 220pF even.)

It is meant to lower the input signal and form a 10Khz low pass filter. I will swap that one out for two resistors and a new cap.

Quote from: duck_arse on July 09, 2017, 11:32:18 AM
I hope some of this is correct, and helps.

It really does, thank you for helping me Stephen.

Closing up on version 1.0 so here is a demonstration I recorded early this Sunday morning. I use a 73' Gibson Les Paul (standard) with dead strings going into a clean Fender Blackface clone via one SM57 and one ribbon mic. In my DAW I added a small amount of top end boost (+2.7dB). That is more information than you really needed! But hey, you are welcome anyway! ;)

I regret ever referring this pedal to be clean sounding. :icon_biggrin: 

https://www.youtube.com/embed/XOCO0-fiCTk (https://www.youtube.com/embed/XOCO0-fiCTk)

I made a lot of fixes and reconfigurations suggested by Duck and Rob in this version (but not all yet). There was a lot of small mistakes on my part and leftovers from previous builds of the project. Some unnecessary resistors and capacitors got kicked out of there.

0.95 Update
1. Removed the output opamp (had enough level without it). I also moved the opamp configured as high pass filter from the end of the circuit to the end of the power amp section, the preamp did not really need more shine.
2. Removed a lot of redundant resistors.
3. Increased the high pass filters capacitor from 680pF to 1nF.
4. Reversed the switch to the power amp and hooked up one of the switch pins to 1/2Vcc, so the opamp would not be left floating when the power amp is bypassed. A great idea by Duck!
5. As a precaution I added a 50pF cap in parallel with the input cap switch in case it would fail. Also a good idea from the Duck.

(http://i.imgur.com/UPpABxA.jpg)

That has a lot of character, well done! \m/

clean sounds - clean, like my sheets.

I really liked the first switch to the mid-cap position. (I think "attenuator" was the word you wanted.)

also, my comment about the 50pF on the switch, I meant to have that smallest value hard connected around the switch, so the switch will have a position with no cap on. so if the switch fails in all other positions, you still have (your fave) 50pF connected. and all the other values can be 50pF less than design value, and switch-in in parallel w/ 50pF.

also, your latest image (circuit?) shows as broken-link.

Quote from: duck_arse on July 11, 2017, 12:00:10 PM
clean sounds - clean, like my sheets.

I really liked the first switch to the mid-cap position. (I think "attenuator" was the word you wanted.)

also, my comment about the 50pF on the switch, I meant to have that smallest value hard connected around the switch, so the switch will have a position with no cap on. so if the switch fails in all other positions, you still have (your fave) 50pF connected. and all the other values can be 50pF less than design value, and switch-in in parallel w/ 50pF.

also, your latest image (circuit?) shows as broken-link.

Yes, "attenuator" was the word I was looking for! I must have read you comment in a rush the first time around, moving the 50pF all together down to the board is much more logical and better idea.  ;)
Anything above 150pF as input capacitor is overkill for me. THE BASS, oh the bass.. Probably because I used 6,8uF coupling caps in the rest of the circuit.

Forgot that I resigned from my previous hosting company but all content is up-to-date on a offline storage. Phew.. Here is a Shiba Inu to still the tingling nerves.

Sorry but I have to ask just to be sure I got this right. The ratio of the voltage divider (R20 4,7k / R21 33Ω) is around 142:1.  If I would change these to either 47k/300Ω or 500k/3,5k (also around 142:1) would the voltage divider give the same performance as the with current values?

the voltage should divide the same, yes. but you can also then scale your feeding cap in the opposite direction - R times 100, C divided by 100. if you keep the massive 6u8, you may get blocking distortions.

Quote from: duck_arse on July 14, 2017, 10:59:30 AM
the voltage should divide the same, yes. but you can also then scale your feeding cap in the opposite direction - R times 100, C divided by 100. if you keep the massive 6u8, you may get blocking distortions.

I don't get it? ??? Reverse C17, and why? What is this blocking distortion you speak of? :o  ;D

no, no reverse. reduce the cap value by the same factor as you increase the resistor values. so if your 4k7 goes up to 470k, your 6u8 goes down to 68nF. the two resistors are the load for the previous stage, and the cap feeding that load forms a low-pass filter. if you work the numbers, you'll see.

blocking distortion comes from cap values too big for their purpose, so they "charge up" some with signal, and the DC level shifts, "blocking" signal. so you get a whumping dip in your output level, slowly comes back to normal till you hit another chord, then whumps down again. [you'd be better if an expert corrected this mess I've put.]

Quote from: duck_arse on July 14, 2017, 11:13:38 AM
no, no reverse. reduce the cap value by the same factor as you increase the resistor values. so if your 4k7 goes up to 470k, your 6u8 goes down to 68nF. the two resistors are the load for the previous stage, and the cap feeding that load forms a low-pass filter. if you work the numbers, you'll see.

blocking distortion comes from cap values too big for their purpose, so they "charge up" some with signal, and the DC level shifts, "blocking" signal. so you get a whumping dip in your output level, slowly comes back to normal till you hit another chord, then whumps down again. [you'd be better if an expert corrected this mess I've put.]

Of course, I should have though of that! So that is blocking distortion. I never had a clue and never encountered that problem. Thanks again Duck now I can finish this.

With all problems and calculations out of the way a brand new layout and a updated schematic are inbound tonight!

Things got delayed but here are the new layout and the latest version of the schematic.  Just in case somebody wants to build one know that the layout is unverified but I am fairly positive that everything is in order. I will start assembling one tomorrow.

Layout (PDF Download):
http://tropicalhippo.com/GreenMujina/Green%20Mujina%20-%20Layout%200.97.pdf

Schematic full sized:
http://tropicalhippo.com/GreenMujina/Green-Mujina-Schematic-0.95v.jpg

(http://tropicalhippo.com/GreenMujina/Green-Mujina-Vero-Layout-%28v0.95%29.png)

(http://tropicalhippo.com/GreenMujina/Green-Mujina-Vero-Layout-CUTS.jpg)

(http://tropicalhippo.com/GreenMujina/Green-Mujina-Schematic-0.95v.jpg)

Attention!  R5 is wrong in the layout. It is obviously not supposed to be a 56k, the correct value is 1k. I am out on a long trail now but I will update the layout as soon as I am back home again.

Update: I had to move the last two JFET stages one step to the left. I had for got to separate R20 from Q4s source, R22 and C19 but that is fixed now. Soon done with my build and I will report back if the latest layout can be greenlit.

New Layout (0.99v) PDF:
http://tropicalhippo.com/GreenMujina/Green%20Mujina%20-%20Layout%200.99.pdf

Click for full size:
(http://tropicalhippo.com/GreenMujina/Green-Mujina-Vero-Layout-%28v0.99%29.png)

I finished the vero and everything works now that all the f-ups with the previous layout has been dealt with. C1 and C23 was connected wrong in the previous layout and the first part of IC1 was missing a bias resistor (R13). If you have already built it (or are in the middle of building it) I hope you can correct your build without too much hassle. I am truly sorry for the inconvenience.  :-\ For anyone building this for the first time enjoy the crushing weight that comes with this savage!  ;D


A high resolution PDF file with everything you need: tropicalhippo.com/GreenMujina/Green%20Mujina%20-%20Layout%201.00.pdf (http://tropicalhippo.com/GreenMujina/Green%20Mujina%20-%20Layout%201.00.pdf)


(http://tropicalhippo.com/GreenMujina/Green-Mujina-Vero-Layout-%28v1.00%29.png)
(http://tropicalhippo.com/GreenMujina/Green-Mujina-Schematic-1.00v.png)
(http://tropicalhippo.com/GreenMujina/Green-Mujina-Vero-Layout-1.00v-CUTS.jpg)



Here are the measurements from my working build with a 440Hz sine wave at the input.

Q1
D. 9.25
S. 0.28
G. 0.00


Q2
D. 9.14
S. 0.19
G. 0.00


Q3
D. 9.23
S. 0.31
G. 0.00


Q4
D. 9.82
S. 0.33
G. 0.00


Q5
D. 9.19
S. 1.24
G. 0.00

IC1
1. 9.25
2. 9.25
3. 9.25
4. 0.00
5. 9.19
6. 9.25
7. 9.25
8. 18.51

IC2
1. 9.25
2. 9.25
3. 9.25
4. 0.00
5. 6.27
6. 6.37
7. 6.47
8. 18.51

Hi,

I was ready with this beauty but by the time I had finished the enclosure and hooked everything up the Power Amp section was no longer functioning. Tired and angry, I took the build apart and started probing for the failing link and measuring the voltages. All pins looks fine except Q6, it is impossible to drain down to 1/2 Vcc. It does not nudge away from 18v.

Before I discover the issue with Q6 I did notice something that may also be a clue to why the Power amp section is not working. If I probe audio from R10 (just before Q3) and disconnect one of the legs of C13 or switch on the power amp section the signal goes out. Is C13 acting as some sort of gravity that pulls the signal forward? Maybe that gravity is decreased when the power amp section is active?

Anyways, I will try to fix Q6 and see if it is causing this issue.
(http://tropicalhippo.com/GreenMujina/Green-Mujina-Schematic-1.00v.png)

Thought I confirm the build and post the verified documents. If you have any problems just ask here and I will try to help you out.

A high resolution PDF file with everything you need: tropicalhippo.com/GreenMujina/Green%20Mujina%20-%20Layout%201.00.pdf (http://tropicalhippo.com/GreenMujina/Green%20Mujina%20-%20Layout%201.00.pdf)

(http://tropicalhippo.com/GreenMujina/Verified/Green-Mujina-Schematic-1.00v.png)
(http://tropicalhippo.com/GreenMujina/Verified/Green-Mujina-Vero-Layout-%28v1.00%29.png)
(http://tropicalhippo.com/GreenMujina/Verified/Green-Mujina-Vero-Layout-1.00v-CUTS.jpg)

Since the video got lost on page 2 I'll post it again. Sorry for all the rambling, I lost the words a couple of times because I'm not really comfy about speaking into to a camera.

Finally wrapped up a proper demo of this pedal. If you are into weird tones and heavy doom/sludge riffs you'll probably enjoy this one.

A plead for help here, would anyone of you gentlemen to try to figure this out with me.

With the pedal in "Preamp mode" the treble and bass knobs works as planned. 8'oclock full cut, 4'oclock full boost. But when engaged in "Power Amp" the bass control starts effecting the sound backwards. Full bass now becomes a bass cut. I have never experienced anything like it. With some time off the building and this pedal I have come back and realized that the circuit needs improved mid response even future so right now I'm working on that too. Also looking into fixing the +10-15kHz oscillation when the treble is maxed out. Probably just needs some filtering after the EQ stage.


EDIT: um.. I just removed C6 and still got signal coming out. There is something very wrong in the layout or maybe leakage due to extreme levels...

EDIT 2: Signal issue is resolved and I have also found one of the sources for oscillation when the pedal is pushed into heavy distortion and boosted Treble, Bass or Grain. This also eradicated the backwards response of the bass when the pedal has the power amp engaged, very strange behavior. All good now but still not perfect.

...Turned out that the final high pass stage was guilty for a lot of the oscillation. The oscillation often begins when maxing out both pre/poweramp volumes in combo with some EQ boost or with the "Grain" boosted. So here is a new question: Have I calculated the high pass correctly or what? Should cut around 4,2Khz if my calculation is correct? 1/(2*PI*R28*C23). If I have then perhaps I could lower its gain but keep the same frequency center and check if that stops the squealing.

Now, I really like the sound with the last stage in but the oscillation ruins it. It seems to add more distortion (probably due to the oscillation) but strangely also a more bass/mid pronunciation going on. That is why I am suspicious about my calculation. If I do lower the gain of the high pass filter (= less oscillation and less distortion) then I could try and "up" the value of R24 to regain some dirt. What you think?
Take a listen, first with the HPF then with it bypassed: http://tropicalhippo.com/GreenMujina/Green%20with%20and%20without%20High%20Pass%20Stage.wav

(http://tropicalhippo.com/GreenMujina/Geeen-Mujina-High-Pass.png)

I don't think that opamp is biased. is it a special type? also, wouldn't the feedback resistor connect to the pin2, instead of the R//C junction? with a 1M from pin 3 to V/2, you should be able to drop the value of C22 to 10nF or thereabouts.

Duck, I have no idea. Help needed.  ;D
It just a OPA2134.

well, I only have little idea - but I'd first try move that resistor connection, and put some sort of bias resistor on (+) pin, see what results.

good luck.

Quote from: duck_arse on January 14, 2018, 10:08:54 AM
well, I only have little idea - but I'd first try move that resistor connection, and put some sort of bias resistor on (+) pin, see what results.

good luck.

Thank you for the help Duck! It's very helpful that someone with more knowledge than myself takes a gander on this thing here. I appreciate it a lot.

(http://tropicalhippo.com/GreenMujina/Geeen-Mujina-High-Pass2.png)

While this new configuration probably is the way to do it and the "sound" is still intact the power amp still oscillates badly, like before. Maybe adjust R29 and see if I can lower the gain of the full signal.

Changing the value of R29 did not help. Then I guess it's just the layout left then and/or the oscillations starts somewhere else?

do you have supply bypass caps right on/at the opamp supply pins? work out and list the conditions - when it does oscillate and when it doesn't, switch positions and pot settings, like that - and one of the oscillation experts might be able to help.

Big Edit:
Oscillation is now beaten like a low life scum from the smokey, shit steaming streets of everybody's favorite rotten-apple-city (read that in a joyful tone). On top of that some other improvements have made this sucker kick ass even better than before! More pick attack,More versatility and More creamy mid range. Updated schematic (and layout) inbound soon.

Audio probed my way through the power amp again and realized the major feedback/oscillation starts after the opamp that follows the "Grain Filter". It is the first half of the last OPA2134 (A) that has R20, R19 and C17 connected to it. Now, oscillation stops if I bypass the last opamp stage OPA2134 B with R28,R29 and C23.

(http://tropicalhippo.com/GreenMujina/Verified/Green-Mujina-Schematic-1.00v.png)

Quote from: stonerbox on January 14, 2018, 09:39:00 AM
...Turned out that the final high pass stage was guilty for a lot of the oscillation. The oscillation often begins when maxing out both pre/poweramp volumes in combo with some EQ boost or with the "Grain" boosted.

Quote from: duck_arse on January 15, 2018, 08:54:04 AM
work out and list the conditions - when it does oscillate and when it doesn't, switch positions and pot settings, like that - and one of the oscillation experts might be able to help.

I did in an earlier post but as it was buried in a wall of text I can't blame you for missing the diagnose the first time.

some I miss, some I just ignore ......

you going to update the vid as well?

Quote from: duck_arse on January 15, 2018, 09:54:00 AM
some I miss, some I just ignore ......

you going to update the vid as well?

That is one way to do it. If I find time I will mic it up  through a Laney Pro Tube and post a video with some settings/examples.
Incredible what these fairly simple updates has done for this thing, not only in mid range and clarity but the EQ section and Grain just got about +100% boost in response. Gotta love it when EQs and mid boosts does 200% in damage.  ;D

So what was the problem? You removed the last op amp section?

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

Quote from: rankot on January 15, 2018, 12:36:27 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!

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]
(http://tropicalhippo.com/GreenMujina/Green-Mujina-Schematic-1.20v.png)

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).

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.

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.

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.

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.

(http://tropicalhippo.com/GreenMujina/Green-Mujina-Schematic-1.20v.png)

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 (http://tropicalhippo.com/GreenMujina/noise.wav)

Could you post a pic or two of the build?

Quote from: EBK on May 18, 2018, 05:43:25 AM
Could you post a pic or two of the build?

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

(http://tropicalhippo.com/GreenMujina/GUTS%201.JPG)
(http://tropicalhippo.com/GreenMujina/GUTS%202.JPG)
(http://tropicalhippo.com/GreenMujina/Verified/Green-Mujina-Vero-Layout-%28v1.00%29.png)
Edit: Done.

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.

Quote from: EBK 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.

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.

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.

Quote from: EBK 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.

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?

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?

Quote from: EBK 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?

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.