Morula

[anotherjim]

For Depth or Volume controls, a log pot almost always gives a better feel than linear pots.

Ordinary 5mm RED LED's have worked best for me in the past. I think 3mm were the same, it's just that I had more 5mm to use.

Quote

    LFO thumping is because there is no power supply filtering.

How should I add good enough power supply filtering to kill the thump sound? By putting a 100R resistor in serie with a 100µF cap between +9V and Ground ?

Yes, that should help. With the filter and LFO in the same chip, thumping or ticking from the LFO always has a chance of getting into the audio path. All you can do is fit a supply filter and hope for the problem to be reduced below notice.

[snk]

Thank you for your help and advices.
In the meantime, i made some experiments, which may be interesting if anyone wants to build it later.


POWER SUPPLY & THUMP NOISE
- I put a 100R resistor in serie with a 100µF cap between +9V and Ground, but didn't hear much change. However, I noticed two things :
1- I had previously put a booster after the pedal (because before the Morula i had another pedal i'm tweaking with a very low output level), so when i came back to a fresh, normal signal chain (with only the Morula), the "thumping" was barely noticeable (not more noticeable than some clock ticking noise i can get from some vintaeg phasers, for instance), and not noticeable when processing sound (only during silence).
2- I noticed that the thump is audible only at faster RATE speeds (in the second half of the pot). With slower rates, the sound is clean.
Out of curiosity, is there anything else to try in order to kill the thump (If not, it is not an issue, as the sound is low, and often present)?


RATES
- I had read somewhere that increasing C6 could make the RATE slower. So, i swapped the 100µF for a 220µF i had laying around, but i didn't notice a very different behaviour : both slowest and fastest speeds seem to be still the roughly the same.
Any other hint to reach slower RATE values ?


FILTER SOUND
- I tried different cap values for C2 and C4 : decreasing them produce a softer sound, increasing them create a more resonant sound. 6.8nF is very resonant, and quite far from the original sound. 1nF makes a softer sound, less a wah sound, more a pseudo-phaser sound.


DEPTH
I tried a 100K LOG pot for the depth, it improved a little bit the beginning of the turn, but didn't change much. I need to try with a 50K (or even a 25K, as i don't hear much change after 1/4 of the turn).

[anotherjim]

The real timing cap is C7. Increasing that slows it down.

[snk]

I just tried : it's perfect
4.7µF is a bit too much, but 2.2µF is great.
Thank you !

[snk]

Out of curiosity, I one wanted to let more bass pass through, should we increase C3 ?

[Kipper4]

Out of curiosity, I one wanted to let more bass pass through, should we increase C3 ?

I thought that at one time, needs more bass.
The trouble is the best freqauncies to mix back in are the higher ones.
Mixing in more bass you might think will make it sound thicker and more rounded maybe?
It can get muddy quick iirc.

[snk]

it's more a matter of curiosity. I know that some effects (like distorsion) need to cut some bass to sound better, and wahs put the emphasis on mid frequencies.
But this effect was designed as a bass effect, and from my tests it doesn't sound very bassy.
I'm fine with that (i think i will use it on an electric piano), but as i have tweaked most of the parameters and components, i'm telling myself that i could try a couple more things before boxing it into an enclosure

[PRR]

The Depth pot looks backward (has this been mentioned?). Swap wires 3 and 2. It may work smoother (and no crap-out when full-down).

[anotherjim]

The Depth pot looks backward (has this been mentioned?). Swap wires 3 and 2. It may work smoother (and no crap-out when full-down).

You're right Paul. I think everyone has missed that!
No wonder LFO thumping came through - the oscillator is being shorted out when depth is turned down.
Rewire as Paul said!

[anotherjim]

On how it sounds -  it is an auto filter only in a primitive sense. A "proper" one sweeps up and down (or down and up) in response to each note played. That has a good effect because the start of a plucked note is when it has the richest harmonic content - more for the filter to dig in to. You can build on that by having a distortion BEFORE the filter so it has even more harmonics. When you have a filter that's being continuously swept as this one is, using pre-distortion is a good idea if you want to hear the filtering well into the note decays when the plucked string is down to just fundamental tone.

[snk]

The Depth pot looks backward (has this been mentioned?). Swap wires 3 and 2. It may work smoother (and no crap-out when full-down).

Hi, PRR
You are right ! It works much better
Now, with the correct wiring, I think that a linear pot may work better than the LOG i had tried... I will try tomorrow.
With all the mods, I am really enjoying this simple circuit...
I will make an updated veroboard layout, if anyone is interested to build it later. Thank you all for your help !

[snk]

Hello,
This is an updated layout i did, with the DEPTH wiring fixed, and added power supply filtering.



I didn't add the other mods & tweaks I have done, as i am still experimenting with the circuit.


By the way, what do the 10nF and 4.7nF capacitors at the input do (C1 & C4 on the schematic) ? Are they here for filtering out the bass ? C1 seems to be the input cap, and C4 in the filter loop, along with C2 & C5 (both 2.2nF)...