question about the bass balls

[Marcos - Munky]

I´m building an Bass Balls clone right now, and I´m almost finishing it (the onboard part, didn´t started the offboard part yet). But I still miss one part, the 0,47uF tantalum cap. I did a search in the local stores and didn´t found it, the only things I found are a polyester cap and a box cap, both non polaryzed. There´s any problem using them on the Bass Balls, or should I use a polaryzed cap? Here´s the schematic:

http://topopiccione.atspace.com/pjimages/EHBassBalls.sch.gif

The cap is C3 on the schematic.

[Mark Hammer]

You can use a non-polarized cap if you want, or even a 1uf polarized cap.  That component provides DC blocking and bass-trimming for the signal being detected by the rectifier portion.  The circuit will likely perform  no different with values between .33uf and 1uf.  Once you go below .33uf, you would start to notice the reduced responsiveness of sweep to low notes, and the "fuzz" would probably start to lose a bit of its oomph.

[Marcos - Munky]

Thanks a lot, Mark. I will stay with the non polaryzed cap. I hope to finish it this week. Just another question, I read somewhere that the Bass Balls have a loud output, but saw the photo of your build on your site and noticed you didn´t used a volume pot. Is the output volume louder than the bypassed sound in your build?

[Mark Hammer]

The clean filtered output is not really that different from bypass, but the "fuzz" output uses the output from the gain stage driving the rectifier, such that when you turn the sensitivity up (and this often results in more output from that very gain stage in a great many designs), you not only get more sweep but you also get more volume.  EHX threw it in as a something-for-almost-nothing (the cost of a switch, cap, and two resistors) option.  Some folks like the clipping produced by the 1458 chips.  I'm not one of them.  I elected to replace the resistive divider network that attempts to bring the fuzz signal near the clean level by using a pair of clipping diodes.  So, if you replace R8 with a 4k7-10k resistor, and R9 with a selected pair of GE diodes, you'll be able to get something that yields a fairly tight balance between clean-filter/fuzz-filter and bypass.  With that change, turning up the sensitivity control will get you more sweep, more clipping, but modest change in level.  Note that when the sensitivity control  is turned down, regardless of whether you use the mod I describe or the original parts, you will still have less output in fuzz mode than in bypass.

Of course, if you like the 1458-generated distortion, then it may well be a smart move to replace the 47k fixed resistor at the output with a 50k volume pot.

I've made 3 of these beasts, each with different configurations.  I would recommend installation of a simple decay control that replaces R7 (330k) with a 33k-47k fixed resistor in series with a 500k variable resistor.  Faster decays sound much more synth-like.  I've gone with panel mounting the two filter tuning trimpots in past, but in retrospect, panel-mounting just the trimpot from the upper/higher filter (T2 in the schematic) is sufficient for introducing lots of stagger between filter sections and tonal changes. 

I would also recommend use of a filter-balance pot.  Find the pads for R11/R16 and remove the resistors.  Run the output of each filter to a 470R-1k fixed resistor, and solder those fixed resistors to the outside lugs of a 5k-10k linear pot.  Connect the wiper of the pot to C8.  When the balance is shifted to primarily the upper filter, it sounds like a Dr Q.  In tandem with the filter stagger control, the balance control can yield a lot of different sounds.

Three simple additions to the circuit that increase the functionality considerably.

[Marcos - Munky]

Thanks again, Mark. I will try your suggestions. I didn´t got to finish it yet (I´m out of 10K pots , and have some exams in college), but I will finish it as soon as I can.