JHS Morning Glory V4  [traced]

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Manfred
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Post by Manfred »

In the above circuit with the LM833 IC the circuit to generate the half voltage and the bias resistor to the positive input of the OP-Amp are missing.
HalfVoltagBias.jpg

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Matlevo12
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Post by Matlevo12 »

Thanks a lot.
I feel quite stupid about it, but tracing a pedal in the middle of the night probable didn't help.
The track labeled "NOTHING" was disappearing below a smd electrolytic cap, not being connected to anything, and the best answer I could find was "AH ! It's a trick ! They want us to think it's connected to +9V when it's actually not and it's somehow making sense and helping with the circuit ! ".
Yeah I know, not very smart. In reality the elec cap got hit (my fault probably) and it broke one of the tracks. Boring, huh ?

I'm finishing to trace the extra gain stage, I'll post the end results once I'm finished.

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jhergonz
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Post by jhergonz »

Matlevo12 wrote: ↑13 Jan 2021, 14:41 Thanks a lot.
I feel quite stupid about it, but tracing a pedal in the middle of the night probable didn't help.
The track labeled "NOTHING" was disappearing below a smd electrolytic cap, not being connected to anything, and the best answer I could find was "AH ! It's a trick ! They want us to think it's connected to +9V when it's actually not and it's somehow making sense and helping with the circuit ! ".
Yeah I know, not very smart. In reality the elec cap got hit (my fault probably) and it broke one of the tracks. Boring, huh ?

I'm finishing to trace the extra gain stage, I'll post the end results once I'm finished.
Hi, any news? the last stage looks like a Tube screamer tone control without the Potentiometer.

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Matlevo12
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Post by Matlevo12 »

jhergonz wrote: ↑13 Mar 2021, 15:32 Hi, any news? the last stage looks like a Tube screamer tone control without the Potentiometer.
Hi,

I still need to finish tracing it, it's honestly more complex than the V3 or first V4. I should be able to do it by the end of march !

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Post by jhergonz »

Matlevo12 wrote: ↑15 Mar 2021, 09:36
jhergonz wrote: ↑13 Mar 2021, 15:32 Hi, any news? the last stage looks like a Tube screamer tone control without the Potentiometer.
Hi,

I still need to finish tracing it, it's honestly more complex than the V3 or first V4. I should be able to do it by the end of march !
thank you. Will wait for it patiently.

If you need help tracing the circuit, I will be glad helping you. 😁

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Post by Matlevo12 »

jhergonz wrote: ↑15 Mar 2021, 13:04 thank you. Will wait for it patiently.

If you need help tracing the circuit, I will be glad helping you. 😁


There you go, I "Finished" tracing.
I can't see straight, my eyes hurt :)

Careful, it's not easy on the eyes.
Here's a png export (max size) from EasyEDA, if anybody wants to modify it I'll be happy to share it (if that's even possible, though).
I checked everything at least two times, but a different pair of eyes always see things differently, so don't hesitate if you want to check a specific part, I can share pictures of the PCB if you want.

https://i.postimg.cc/GpGb01PF/Schematic-JHS-MG-V4-rev-1-5-2021-03-29-22-54-26.png
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Schematic-JHS-MG-V4-rev-1-5-2021-03-29-22-54-26.png
Last edited by Matlevo12 on 29 Mar 2021, 20:57, edited 2 times in total.

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jhergonz
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Post by jhergonz »

thanks for sharing your schematics.

The image is blurry, I don't know if it is because I'm looking thru phone or it is really blurry.

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Post by Manfred »

Thanks for sharing the schematic.
could you please post the schematic with a higher resolution.

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Post by Matlevo12 »

Hi.
I updated the link and image.
Just click on the image, you can download it afterwards, it's pretty big already. If that doesn't work from your phone there's an option somewhere in your browser to show the desktop version.

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Post by jhergonz »

using multiple zeners for biasing, that's cool.

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Post by Matlevo12 »

jhergonz wrote: ↑30 Mar 2021, 00:20 using multiple zeners for biasing, that's cool.
Now that makes sense, thanks :)

I'm wondering if I should try and put a cap similar to C32 (if I manage to measure it) between Vb and gnd on my noisy v4 (rev1 I guess, the one I traced I few months ago... the main reason why I did this whole thing to start with by the way).
Here is the post/schem (from this very thread), I'm talking about the bottom part : viewtopic.php?p=283525#p283525
Any ideas ?

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Post by jhergonz »

Matlevo12 wrote: ↑31 Mar 2021, 14:39
jhergonz wrote: ↑30 Mar 2021, 00:20 using multiple zeners for biasing, that's cool.
Now that makes sense, thanks :)

I'm wondering if I should try and put a cap similar to C32 (if I manage to measure it) between Vb and gnd on my noisy v4 (rev1 I guess, the one I traced I few months ago... the main reason why I did this whole thing to start with by the way).
Here is the post/schem (from this very thread), I'm talking about the bottom part : viewtopic.php?p=283525#p283525
Any ideas ?
c32 is there to filter the Vref of that opamp, same with C27,30,34 and c40.

but every opamp have their own vref, maybe to ensure that every gain stage's VRef is isolated to other's Vref, to make sure that noise level is low. I don't know if it is necessary, but if it works, it's fine.

try to do what you plan to do, and make it as close as possible to the opamp.

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Post by jhergonz »

if you'll also notice, c5 is now connected to ground instead of Vref, maybe that will also makes the noise level low.
.have you compared the V4 with two IC vs the V4 with more IC?
.I'm quite curious about how different they are to each other.

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Post by jhergonz »

Just finished building the first schematics of Morning Glory v4 with some changes,

I didn't connect the Negative Feedback of the first opamp into the Vref, instead I connect the capacitor to ground.

I add some more 100nf capacitor to the DC supply path and Vref Path, and put them near the ICs +v pins and the 3rd opamp to filter some noise.

i used TL072 because i don't have LM833.

I can't say that it is verified because i don't have the original to compare, but it works and it is awesome.

No popping sound, no unwanted noise.
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Post by ascianabhro »

Can you share the printable pcb image, Thanks

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Post by Matlevo12 »

jhergonz wrote: ↑01 Apr 2021, 19:17 Just finished building the first schematics of Morning Glory v4 with some changes,
Wow, that's cool, which schem did you base your mods on ?

I compared the two V4, but my v4 is REALLY noisy (like synth fuzz noisy) when I turn the knobs up in the red mode so...
The V4 rev 1.5 is dead silent on comparison, probably because off all the independent bias voltages, and probably with that negative feedback to ground.
I measured them, just in case that interests someone :
Power supply
8.86V

UC1
3 4.07
5 4.12

UC2
3 4.13
5 4.12

UC3
3 4.43
5 4.44

I'm going to try the two mods on my v4 rev 1 :
- negative feedback of the first opamp to ground instead of Vb
- 100nf cap between Vb and gnd close to the second opamp

EDIT : Just tested the two mods. The fuzz drone is STILL HERE. STILL. If anyone has an idea before I DETROY THIS CURSED PEDAL, I'm all ears :)

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Post by jhergonz »

how about replace the opamps with tl072

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Post by Matlevo12 »

jhergonz wrote: ↑03 Apr 2021, 00:40 how about replace the opamps with tl072
Thanks !
I did that before, I thought the oa were the problem, the noise was still there.

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Post by bmxguitarsbmx »

The excess noise might come from the zener bias points. Even though the zener is bypassed by a cap, a zener is still quite a low output impedance and the bypass capacitor is hard pressed to compete. Zeners are touted as excellent noise sources and are most often avoided in sensitive equipment. There are some examples and a good solution is to put small resistor between the zener and the bypass capacitor to raise the zener output impedance to a point where the capacitor can do its job. Think of the series resistor as a voltage divider with the capacitors ESR for a reasonable value.

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Post by Matlevo12 »

bmxguitarsbmx wrote: ↑12 Sep 2021, 18:44 The excess noise might come from the zener bias points. Even though the zener is bypassed by a cap, a zener is still quite a low output impedance and the bypass capacitor is hard pressed to compete. Zeners are touted as excellent noise sources and are most often avoided in sensitive equipment. There are some examples and a good solution is to put small resistor between the zener and the bypass capacitor to raise the zener output impedance to a point where the capacitor can do its job. Think of the series resistor as a voltage divider with the capacitors ESR for a reasonable value.
Thanks a lot for this.
The noise problem I have is on a v4 rev 1 version though (from this post : viewtopic.php?p=283525#p283525, the one I had with zener biasing (rev 1.5) worked perfectly, without any noise at all.

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