Morula Bass Auto-Wah help

[lykwydchykyn]

I built a Morula using this perf layout.  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?

[PRR]

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.

[lykwydchykyn]

(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.

[lykwydchykyn]

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.

[lykwydchykyn]

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.