Ehx bass balls mod questions

[disabled_shredder]

I've seen a lot of threads on DIY bass balls pedals and mods but I want to know what can I do to my original pedal I like the sweep ok but despise the distortion. Any ideas or links to sites or threads that cover mods in detail? I saw one thread about an attack mod and getting the second sweep inverted. I'm shooting in the dark so this could somewhat be in your hands. I don't need a walk through I just would like some creative guidance. Thanks in advance to anyone that could help

[Kipper4]

Wheres Mark Hammer when you need him?

[Gus]

Type "bass balls" in the search at the forum  also look at the old forum
Or try "EH bass Balls mods modifications" in a search engine

[Mark Hammer]

Wheres Mark Hammer when you need him?

Well, at 5:32AM, I'm BLOODY WELL ASLEEP!

If it is an older folded-steel box Bassballs, with thru-hole parts, there is lots you can do with it to make it a more fun, and versatile pedal.  You start with a schematic, courtesy of AlexPetrini:

The first thing you can do is replace the trimpots T1 and T2 with panel-mounted 10k pots.  Realistically, T2 makes the more practical difference, so feel free to leave T1 in place.  These "tune" the filter sections.  Being able to adjust the upper filter permits for variable "stagger" between the two filter sections, for a wider variety of sounds, including the classic BB sound.

R6, C4 and R7 set the "time constants" of the sweep.  R6 determines how quickly C4 charges up (Attack), and R7 determines how quickly it discharges (Decay).  You can vary the value of R6 up to a point, but abandon any thoughts of a slow "pad" type upwards filter sweep.  Won't happen.  However, values of 33R 100R and 330R will get you different senses of "urgency" to the sweep and will still prove useful.

The more helpful mod is to replace R7 with a 47k resistor in series with a 500k pot (wired as variable resistor), to produce a wide range of decay times.  Fast decay time (lower resistance) sounds more synth-like.

The "fuzz" produced by the Bassballs has it froggy-voiced charms, but has one nasty issue in that it's volume varies with the Sensitivity setting.  If you want more sweep, you need to accept louder output.  One solution to that dilema is to replace R20 - the 47k fixed resistor on the output - with a 47k/50k  log pot, so that you can dial back volume if needed.

What I elected to do was replace R8 with a 10k resistor, and R9 with a back-to-back pair of clipping diodes.  This not only produces a more conventional "fuzz" sound, but also clamps the output at a maximum, set by the diode properties.  One would need to experiment to find the optimal dioddes, depending on the forward voltages of the specific diodes.  For example one might find that an optimal tone/level is achieved by a schottky in one direction and series pair of germaniums in the other.

All in all, the added volume pot provides more precision, and requires less trial and error.  But the swap of diode clipping for the "natural clipping" of the 1458 may prove more satisfying, tonewise.

Finally, changing the relative volume of the upper and lower filter sections can provide different tones and feels.  R11 and R16 form a passive mixer of the two filter outputs.  Stock, they are equal value to provide a 50/50 blend.  Replace them with a 5k-10k linear pot, and you'll be able to vary their balance.

You can hear what some of these mods do here: http://www.youtube.com/watch?v=eoAIKHFGOcQ

[disabled_shredder]

Jackpot. Can you send a link to the schem. And it is a molded box w through holes. The pic I posted didn't show up. I will def work on the goodies listed just need to find that schem so can you send a hyperlink txt? Thanks also I know there are threads on the stuff but I am as good at searching as an army officer is at finding his coffee without a specialist. And please don't be offended at that joke it's an inside reference to my army days. Also, I love this forum. I have yet to find a rude person or get bad info on this site!

[Mark Hammer]

I guess the picture isn't showing up at your end.

The schematic and other info can be found here: http://topopiccione.atspace.com/PJ08EHBassBalls.html

[pappasmurfsharem]

Hey Mark,

Just curious why is there a limitation to the attack of the sweep?

[disabled_shredder]

I got the vid and schem. I'm going to work ASAP. Ill post my progress as I get along. I've actually owned 2 of the pedals but sold the first because it just wasn't perfect but had to get another. Also I don't have any shottkey diodes I have 4148 germaniums 4xxx series just not shottkey and bat41 diodes any replacement suggestions and also my baseballs pedal has 4558 and 1458 in it that's correct right? I didn't get to look over the schems and the pots do you suggest Lin or log. Ill post more as I get stumped. But thank you guys sooo much oh also is there a way to add a ramp led by any chance I think it would be neat to have. And mar and kipper- thanks so much a million over.

[Mark Hammer]

Yep, it needs a 1458 to produce the sweep, and a 4558 for the filters.  A BAT41 ought to be fine (it's a Schottky).  There's really no magic forumla for the diode choice, except that you want to get some clipping, and you don't want it to be too loud when switching over from bypass.  So LEDs make a bad choice, and a pair of 4148s with a 650mv forward voltage are also likely a bad choice.  Ultimately, you'll want something that "clamps" the output level at something under 1V p-2-p.  So, for example, a GE with a forward voltage of 300mv and an SI with a forward voltage of 550mv may be "in the zone" (this assumes they are back to back).

The Decay pot can be log or reverse log, depending on whether you want to wire it so that clockwise is slower or faster.  Blend/Mix should be linear.  The replacement for the tuning trimpot can be either log or linear, though linear may be a bit better.

By "ramp LED" do you mean somethng that shows how the sweep is proceeding?

[Mark Hammer]

Hey Mark,

Just curious why is there a limitation to the attack of the sweep?

The attack is set by how quickly the averaging cap (C4) is charged by the rectified voltage coming through R6.  R6 slows down that charging-up by limiting current flow.  Trouble is, if you limit the current enough to make it take a long time to charge up C4, you end up not having enough current to drive the base of the transistors that do the sweeping.  In effect, it will behave as if the Sensitivity pot is set MUCH lower than it actually is.

You can certainly offset that, up to a point, by increasing the gain of the rectifier stage (e.g., higher feedback resistance in the op-amp).  But there are limits to how well that can work.  Alternatively, one can insert a buffer stage between the attack/decay components and the transistors they are to sweep.  But that gets more complicated, and is generally not supported by the boards themselves.  It's just easier to accept a more limited range of attack times.  A VERY fast attack, using something like 22-33R, will sweep upwards fast enough that it sounds like that's where the sweep starts.  In other words, it goes "ow" instead of "wow".  A value of 220-330R will move you into "wow" territory.

Since the decay resistance simply sets how quickly you drain off the charge in C4, its effect is relatively independent of the Sensitivity control.

[disabled_shredder]

Mark exactly I would like a ramp led is that possible if not so what but it would be a cool feature.

[Mark Hammer]

In principle that would simply involve tapping the output of the rectifier gain stage, and using an op-amp to drive something similar to R6/C4/R7, but with a nice superbright LED to ground at the end of it.  The tricky part would be assuring that its most visible illumination is occurring at the points in the sweep that are most informative for you.  And that, in turn, requires you to articulate what sort of visual information would BE informative, and not merely "cool".  So, what do you need it to be able to clearly tell you, and how long does it need to linger, or how quickly does it need to disapear, in order to tell you?

I've mentioned here before that some years back, I made a "blinking robot face" full head mask for my kid for Halloween.  I used a simple envelope follower circuit from the DR Q, fed it with an electret mic capsule inside the mask, and used the envelope follower to lightup two superbright LEDs in the nostrils of the mask, so that they flashed in synchrony with the voice when the wearer talked.  Alternatively terrified or enchanted preschoolers when thyey saw it.  "How does he DO that?"

[pappasmurfsharem]

  Alternatively, one can insert a buffer stage between the attack/decay components and the transistors they are to sweep.  But that gets more complicated, and is generally not supported by the boards themselves.  It's just easier to accept a more limited range of attack times.  A VERY fast attack, using something like 22-33R, will sweep upwards fast enough that it sounds like that's where the sweep starts.  In other words, it goes "ow" instead of "wow".  A value of 220-330R will move you into "wow" territory.

Since the decay resistance simply sets how quickly you drain off the charge in C4, its effect is relatively independent of the Sensitivity control.

Where would you place the buffer for example in the topopiccione schematic. Is it just a simple splice between? I would imagine that would be fairly simple since the enveloper follower is reasonably linear in it's connections.