This Week on the Breadboard: ENGL Powerball (Bolide) Distortion

Chuck D. Bones

Chuck D. Bones

Circuit Wizard
The pedal circuit bears a strong resemblance to the Friedman BE-OD line of pedals. I gotta say I like the tone of this one better. Very nice overtones. Good gain range. I was unsure about the EQ section for two reasons:
1. The TREBLE control is tuned very high up in the freq spectrum; turning the TREBLE knob has very little audible effect.
2. The BASS & MIDDLE knobs have enough range to drive the EQ stage to saturation. Not good.

The simple fix for issue #1 is to increase C21 to 1.5nF or higher.
The simple fix for issue #2 is to run this on 18V.

Another option for #2, one which I favor, is to move the VOLUME control ahead of the EQ section.

More to come...
 
So it uses three dual opamps and the first and last gain stages are on the same opamp. Doesn't this break international safety protocol and possibly lead to the end of the world as we know it? Or have I got that wrong? (Tip: It's highly likely)
 
It is considered good practice to have first and last stages on separate dual opamps, especially when huge gain increases are present (or so I have read in multiple sources). In my very limited experience, I have only had issues if/when overgained signal is entering the last section, or if that section ups the gain substantially. I guess the biasing network also plays an important role there.
 
Agreed. Arrange the layout and device pairing so that it flows from input to output when dealing with high-gain circuits. With low-gain circuits like a phase-shifter, any opamp pairing is fair game.

First two stages - lower right; middle two stages - lower left; last two stages - upper left.

Knobs (L-R): VOLUME - BASS - MIDDLE - TREBLE - GAIN
Powerball Distortion cb mod v0.1 breadboard 02.jpg

Here's the volume mod:
Powerball Distortion volume mod.png

I'm not satisfied with the 3-band EQ, the MIDDLE knob is too broad, it's more like another volume knob.
 
I wonder if this circuit is designed to sound like an Engl amp or work well with an Engl amp? That could possibly help to explain the EQ choices.

I was quite disappointed with the various Friedman pedals I have tried. They sound kinda unfocused to me, like there's too much going on. Which I guess there is, looking at the schematics. It's a bit odd considering the sounds they're supposedly based on. Is this one better overall?
 
Right!
And from Sweetwater:
Plug the ENGL Powerball pedal into your favorite guitar amplifier, and you'll instantly turbocharge it with the paint-peeling high-gain tone of ENGL's Powerball II head. Based on the Powerball II's Lead 2 channel, this distortion pedal employs analog circuitry to faithfully re-create the original amplifier's gain stages. The Powerball pedal gives you a 3-band EQ with ±7.5dB of boost/cut, along with Gain and Volume controls for tailoring your distortion tone. You also get true bypass switching to maintain your tone when the pedal is inactive, along with reverse polarity protection and a second DC jack for easy daisy-chaining. This distortion pedal boasts a durable housing to safeguard against stomp-induced damage. If you want to fortify your clean-voiced amp with metal-worthy dirt, or if you'd like to add an additional high-gain channel to your rig, Sweetwater recommends the Powerball pedal — it epitomizes ENGL's burning modern metal tone.
 
I've been playing around with the EQ stage and I finally settled on this. This mod is too extensive to be practical on a production pedal or a PPCB board. But is does sound good and is very versatile. The TREBLE knob has more range and can get much brighter than the original design. The MIDDLE knob is more focused, but does not get nasal when dimed. BASS range is a little greater. The LEVEL knob is ahead of the EQ stage, which prevents the EQ stage from saturating. It's very easy to customize the EQ by fiddling component values. The Gain Trim adjusts how soon the hard clipper (LED3 & LED4) come in. The stock setting is 8 (3:00) which is pretty aggressive. I replaced the four BAT41s with a pair of 1N4148s (D1 & D2). The Vf is about the same.


Speedball Distortion v0.3.png
 
Funny that you should use gyrators for the EQ - I have been working on a similar arrangement (volume on inverting opamp + gyrator mid control) on a JMP1-based dirtbox, after being disappointed by the bax tonestack in that setting.
Indeed the Friedman similarity is apparent, to the point of wondering if it comes from the same designer. It would be interesting to know how many "shadow designers" there is in the pedal scene: SLO and VH4 pedals look like designed by the same guy, the Suhr Riot sure looks like Wampler, the Revv pedals are very similar to this one too, and so on and so forth.
Not a big fan of ENGL, but I will have to breadboard this one just for the tonestack alone :)
 
Surely, everyone is looking at everyone else's designs.
The Baxandall-style MID control is always going to be broad and unfocused because there is no combination of component values that will provide a Q high enough. I could have left the BASS & TREBLE circuit intact and implemented only the MID control with a gyrator. The parts count would have been about the same as my v0.3.
 
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