I built a Morula using this perf layout (https://effectslayouts.blogspot.com/2019/11/morula-auto-wah.html). The results were a bit disappointing -- it thumps loudly, at high rates it makes zipper noises, and the actual effect is very subtle.
I've been over my build a dozen times, and checked the layout against the schematics as well as suggested mods in other threads on this forum. I upped the power filtering cap to 470uF which helped a bit with the thump, but all in all I don't seem to be getting the magic that other people found in this circuit.
I guess I'm less looking for debugging assistance and more of a sanity check -- has anyone built this and it sounds good? If so, can I pick your brain?
https://www.diyschematics.com/schematics/galleries/Richard-Boop-RLBJR65/album107/Morula_Schematic.gif
> the actual effect is very subtle.
Temporarily wire it like this. {below: new file trick!} Instead of a LFO, turn the knob by hand and see what it does to signal. (prolly want a helper or a loop-recording.)
It may just be subtle. But it is also too easy to get parts mixed-up so it works on wrong frequency bands. Or a low-gain 4049 (today MUST be UBE) may not track well. Maybe one of the wizz-kids can assume the LED acts as 300r to 10k resistor and plot the curves.
Quote from: PRR on September 23, 2023, 12:01:50 AM(today MUST be UBE)
Aghhh, that may be the problem. I have the buffered one; got in in a trade and didn't look carefully before building. Bummer, I don't think I want to invest more money on this build, was mostly just looking to do something with the chips I had.
I'll give your test jig a shake tomorrow anyway, but I'm getting a decent voltage swing on the LFO.
So, FWIW, I did try rigging up +9V to the depth pot and sweeping manually. Two observations:
- The effect was still not very compelling, and what little action there was was in the early part of the sweep, confirming that the LFO is giving a decent sweep already. I'm guessing that by the time the voltage at the LED+ hits the LEDs Vf, the action is done.
- The zipper noise from high rates, and even the clock noise, was present even without the LFO output going anywhere. Clearly we just have a bleed situation here, or some fault in my build.
I'll set this thing aside until fate brings me the proper IC, I guess. Next parts order, I guess.
So, an update if anyone happens to see this: I got a proper unbuffered 4049 and plugged it in. I think the effect is happening, but I also now have a LOUD whistly noise as the sweep goes through some kind of resonance.
Need to go over this again, I suppose. Or take it apart.