Bass balls - very weak effect when in clean mode.

[RandomGlitch]

Hi, I've built a Bass Balls clone, which works pretty well on the 'fuzz/distorted mode but in clean mode it's really weak! Has anyone got any ideas why this might be? Maybe thats normal, but the demos ive heard all seem to give quite a stong effect.

Hope someone can help.  Many thanks!

[Mark Hammer]

One of the weaknesses of the Bassballs is that the "fuzz" mode is much louder than the clean mode.  This happens because the clean mode takes its signal from the output of a unity-gain buffer, and the fuzz signal is taken from the output of the gain stage used to provide the envelope signal.  The 100k/47k divider does manage to drop the fuzz signal down quite a bit, but where the clean signal level does not change as the sensitivity is increased, the fuzz signal does get noticeably louder.  Realistically, the darn thing needs an output level control, or at least a "fuzz level" control.

So, if the clean signal is at about the same level as the bypass signal, but the fuzz signal is a lot louder, what you are experiencing may simply be the inherent design flaw of the unit.

If that is the case, one possible cure is replacing the 47k resistor to ground with a 50k pot, to "tame" the fuzz level as you crank the sensitivity.  Alternatively, what I've done on mine is to replace the 100k/47k network with a 10k series resistor and diode pair (germanium or schottky) to ground.  This does a few things.  First, it produces a proper fuzz (although some folks kind of like the gargly sound of a 1458 breaking up).  Second, it puts a clamp/ceiling on the fuzz level that remains constant, regardless of the sensitivity setting.

[RandomGlitch]

Thanks for repling Mark - Ive read your mods published on the bassballs, and I was expectin to be making use of some if them.

That was once I had this working! It just seems to be getting weaker and weaker!

Signal is getting thru, envelope signal us there, checked rises and falls at transistor basses,
But... Not wah-ing... I'm thinking it could be that my filter capacitors (box type) have gone bad...
Is this likely..  I will check it!

Nearly ready to throw it at the wall!     

[Mark Hammer]

The filter caps are small moulded sealed types.  They probably CAN go bad, but with nearly the the degree that electrolytic types can.  It's not a hard and fast rule, but the ones you want to keep an eye out for when malfunction occurs, might be those of 4.7uf and above; the 100 and up types being more suspect.  But unless you decided to scavenge your caps from a 1963 DuMont television, or used a plumbing soldering gun to install ceramic disc caps whose wax ended up running down the leads as you installed them, its unlikely that the filter caps would be bad.

Even if you feed a signal without any dynamics whatsoever, you should be able to tune the filter sections using the trimpots.  And if you can do that, there's nothing wrong with them. Which turns our attention to the envelope follower section.

Do note that while a wide variety of effects that use an LM1458 can easily accommodate use of many other different dual op-amp types, the Bass Balls needs a 1458 for the envelope follower section.  The filters can be anything you want, and probably the input buffer too, but that gain stage for the envelope part HAS to be a 1458 (which drags along the input buffer for the ride), or else you just won't get decent sweep.  I say this not from merely reading the drawings, but from popping different chips into the socket.  So if you're using something else, that may well be your problem.

[RandomGlitch]

Yes, well I'm fiddling with the trim pots (I've actually made them regular pots), and as I adjust them I get a small amount of the expected wah/filter effect, but not much.

I used the box-type caps, brand new, so nothing funny like you described, Mark.  I thought capacitor failure unlikely too, just seemed to me that if the caps were bad then I effectively be sending the signal through 2 unity-gain op-amp buffers, which would give the symptoms I'm getting.

I'm at work right now, but just perhaps I've swapped my IC's about in this circuit - I definitely bought the right ICs!. I will check later.

If not then I will be replacing the capacitors!

Thanks for your help!

[RandomGlitch]

Update:
I've scrapped my perfboard layout and built a vero layout I found- modifying it
for the external trmmers, blend and decay pots that I'm using.

I reused the capacitors and when I fired it up it was the same as before!

So, I replaced al the capacitors.  It's now better, the filters actually do something!

Now I have a weird, gargling decay and the decay pot does nothing.  This makes
me think that the voltage going to the frequency trimmers(pots) has some AC
or is not being rectified correctly. I temporarilly wired up a.pot as voltage
divider and applied that to the trims - that gives a smooth-sounding wah
as I wiggle the pot. So I'm thinking maybe the diode is screwed.

Anyway will look at it later, this is certainly the trickiest build yet.

Any ideas on debugging gladly received!