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

[Chuck D. Bones]

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...

 

[szukalski]

Nice! I have a couple of Engl tube amps and they always have this unique tonal signature. Your description of the high end rings true!

I didn’t even notice there was a Bolide!

 

[Chuck D. Bones]

Every so often, I have to comb thru the sales side of this website to see what's new. This one caught my eye 4 years ago and then was left to languish in my pedal circuit collection. Until now. I have a few mods in mind. Some minor, some not so minor. Mainly dealing with EQ and headroom.

 

[HamishR]

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)

 

[Blackboarcult]

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.