¨My¨ Modified Bassballs

[Kon_fución]

My next build is going to be a Bassballs and it is going to be used with bass only.
I've made this schematic with information found on the forum and internet, but wanted to have everyones opinions, suggestions, thoughts, mods and experiences before attempting to build this effect.



I'm still thinkin about taking out the fuzz section, changing R14 and R19 to higher values as suggested by Mark Hammer on another post and maybe even lowering the resistors at the base of the transistors to 10K. But as said before, I want your opinions and experiences.
Yes, they are a lot of controls but its going to be my first attempt at putting on-board potentiometers and switches. Anyways, if anyone feels that some controls are not really usefull, let me know.

So... what would you do?

[Mark Hammer]

I can't see your drawing at the moment, because I'm at work, but I cannot emphasize enough how useful it is to be able to vary the decay time by varying that 330k resistance after the rectifying diode.  Fast decays really add a nice zip to the pedal, especially for bass.

[Mark Hammer]

Okay, now that I can actually see it, a few recommendations.

1) Don't make yourself nuts with the ranges for each filter section.  If you simply make the 10k trimpots into panel-mount pots, that will give you more than enough adjustment of the stagger of the two filter sections.  It's also the case that changes to the resonance will shift the centre frequency.  The 6-pack of caps you would need to have 3 ranges for each filter will make the wiring a bloody nuisance.  Save yourself the trouble.

2) The additional averaging caps to extend decay time are also something you'll find to be a waste of your time.  For rhythm strumming, yes, but for bass they end up taking too long for the filters to settle back down.  True, a larger cap can smooth out the ripple during the decay phase, but if you have the decay faster (which the R7/RV5 arrangement will let you do) that also makes any ripple much less apparent.  Sounds much "synthier" too.

3) The two diodes D2/D3 should be parallel to each other, not in series.

4) The volume trimpot will probably make you happier if it is a panel-mount control.  You'll want it to offset the level differences as you adjust the sensitivity in the fuzz mode.  You also drew it wrong.  The output should be from the wiper of the pot.

5) The resonance controls are correct.  Whether you will find they add something useful is another matter.  You'll also find that it'll take lots of pot rotation to produce a discernible difference.  It may simply be easier to replace the 5M pots with a 3-position toggle to select low/medium/high resonance.  So, a switch that adds a 2M2 resistor in series with the 470k resistor, or either bridges the 2M2 (dropping back to stock 470k feedback resistance) or places a 1M2 resistor in parallel with it.  That'll get you 470k, 1.24M and 2.67M, which ought to produce audibly different resonances.

6) R6 sets the attack time.  Though you don't want to make it too large, you'll notice pleasing differences if you have a choice between, say, 47R, 100R, and 220R.  Again, something you can probably do with a 3-position toggle.  When the attack is very fast and the decay longer, it creates the illusion of a downward-only sweep.

7) The Blend control RV5 is a good idea.  Try 10k just to be able to have a lot more of one side than the other.  A 5K pot WILL work, but may not allow you to cancel one of the filters quite as much.

So, that's my recommendation.  I've made several for myself and find that I can get away with as little as 4 knobs (sensitivity, decay, upper filter stagger/tune, and blend) and get a whole whack of sounds that the original can't get.

[Kon_fución]

Great. That's exactly the help I was looking for.
I'm still thinking about the resonance controls... it basically adjusts the peak level and maybe also the shape of point ¨Q¨, correct?

I guess all other modifications, if any more, are going to be ¨try and see¨... or actually, ¨try and listen¨.

... You also drew it wrong.  The output should be from the wiper of the pot.

Oops   

[Mark Hammer]

Okay, just a few more tweaks/fixes.

1) One of either D2 or D3 should be pointed the other way.

2) SW2 might get you popping as shown.  A better arrangement is to have a default resistance of 220R and use a different sort of SW2 to add other resistors in parallel to produce lower resistances.  So, run one side of the 220R resistor to the middle lug of a SPDT on-off-on toggle.  Connect a different resistor to each of the two outside lugs (180R and 68R will do nicely) and join their free ends.  Now connect that point to the other side of the 220R resistor.

[Kon_fución]

Aproved for production, Chief? 

[Mark Hammer]

Pretty much, yeah.  Personally, I don't think you're going to find the dual resonance pots worth the effort, but then that's a matter of taste rather than electronic "correctness".  So, yes, you're cleared for takeoff.  Permission to funkify granted!

[Kon_fución]

OK, here's a Compilation of the Schematic and PCB. I did not include audio samples because I'm having problems with my USB interface.
The circuit is working and sounds just like a normal Bassballs, but with more flexibility. I omitted the Attack control because i heard no audible difference but the Decay control is very usefull for different styles of playing and speeds.
The OP amps I'm using are MC1458 for the Envelope and TL082 for the Filters. The Ripple Filter Capacitor witch used to be 4.7uF I lowered it to 1uF to get a bit of ripple.
Special thank to Mark Hammer.

http://www.megaupload.com/?d=DN69996J  (107.25KB)
If the link is broken email me to maurozaltron@gmail.com and Ill send you the file.

[bluesdevil]

Thanks a lot for sharing. I'm looking forward to trying my hand at building some effects for bass in the near future.

[chicago_mike]

Hey I built this along time ago and fixed the footswitch wriring so it works!!

But, its a little thin sounding for bass. Could I just raise the value of the input and output cap?

[oldrocker]

Do it on a bread board first.  That way you can try out Mark's and your own mods without desoldering a re-soldering.  I built it stock.  It's not too difficult to build but trying different mods could be a hassle.

[alex frias]

Maybe a blend control for mixing non-processed sound with the effected one could be usefull... But, one more knob to fit in...

[chicago_mike]

I put in a larger sized input cap and that helps. And for blending I built my own blender pedal. So I got that covered.

Thanks for the advice guys.

[oldrocker]

For an interesting sound try a 358 in place of a 1458.  It gives the filtering a smoother feel.  Although the 358 renders the fuzz portion almost useless.  I liked it but since I was trying for the original sound I put the 1458 in.

[Mark Hammer]

For an interesting sound try a 358 in place of a 1458.  It gives the filtering a smoother feel.  Although the 358 renders the fuzz portion almost useless.  I liked it but since I was trying for the original sound I put the 1458 in.

I was never a big fan of the original "fuzz" sound, preferring instead to use a diode pair to produce clipping.  So, while use of a 358 might negate the 1458-based distortion, that does not mean one has to go without a harmonically rich sound for filtering.  It's a simple matter to swap the resistive divider that EHX used on the "fuzz" side for a well-chosen diode pair.

[chicago_mike]

I have a bunch of 1N270's and 4148's and leds...

I could switch a pair in and out with a dpdt..

[Mark Hammer]

The thing to remember about the "fuzz" channel on the Bassballs is that it is derived from the envelope follower/rectifier stage and NOT the input buffer.  What that means is that the more you turn up the sensitivity, the louder the output will be.  The resistive divider on the original brings the fuzz output level down somewhere around the range of the buffered clean side, though never exactly the same level.  By using diodes, the maximum loudness of the fuzz channel can be fixed by means of the diodes selected. 

Folks who like to experiment with diodes will feel tempted to consider various combinations.  I caution against this, for two reasons.  Trust me, you do NOT want to flick the clean/fuzz switch and have to volume be 6 times greater than you were expecting; you should ideally be able to achive some form of clean/fuzz balance so that you don't have to run around adjusting levels.  Additionally, you want the fuzz channel to feed the filters with as harmonically rich a signal as possible for as long as possible, which sort of limits your diode choices (forget about LEDs, or a 2+1 Si diode combination).  A 1xGE/1xSI combo comes pretty close to ideal, although a 2+1 GE combo might work well too.

Alternatively, if you had the space, you might consider use of a 3 or 4 position rotary switch that could select between clean, "original" gargley-sounding fuzz, and one or 2 diode-based fuzz sounds.  Since a 3 or 4-position rotary would likely have multiple poles, you might consider having some sort of volume compensation be introduced.  Looking at the topopiccione schematic here, you can see a 47k output resistor.  If that 47k resistor were to be replaced with a resistor "ladder", like a 3k3,4k7, 6k8, and 33k resistor in series, one of the poles of the rotary switch could connect the stompswitch to either the junction of the 3k3 and 1uf output cap, or the 3k3/4k7 junction for a slightly lower output, or the 4k7/6k8 junction for a lower output level, or the 6k8/33k junction for an even lower output level.  The resistor values are not written in stone, and may even be way off from what is required, but the basic principle holds that you could have 2 or 3 different sorts of fuzz settings AND compensate for their different volume levels at the same time.

[chicago_mike]

Gotcha! Thanks for the info Mark.

[fuzzo]

Hi any news about this project ?

I'm wondering about making an eveloppe filter to fill in a EHX box I've. I tried the doctor Q on breadboard and I liked it (expect the distortion introduced by the "element control" , transistor).

Anyway, I've some question about the schematic drew by Kon_fución .

Does the "frequency" pot work good ? What it's role here ? accentuating or cancelling the effect of the transistor on the feedback loop , transistor which is in // with the 47K (to set the maxium frequency ? ) ? (sorry , theory isn't really my thing )

a little bif "off topic" but I'd like to use the mutron 3 enveloppe schematic but (for cost reason) using a transistor (like the EHX stuff ) . Can I juste change the couple LRD/LED by the same structure used in the baseball (I wanna use the  mutron 3 beacause of the "up/down" switch, my enclosure has a hole for a switch).  Even if I could use that switch to change cap in filter section.

Mark Hammer , I read your article on RG's site yersteday about that kind of effect, I really enjoyed it . Simple and interesting .   

[chicago_mike]

Update. The first filter isnt working for me. The second filter and fuzz and all the other controls work.

I swapped the 1st filter sections npn and scoped that section but for some reason pin2 is getting no signal. Everywhere else Im fine.

I swapped quite a few different ic's too...maybe the socket is bad? ..but that looks just fine too.