BBE - Boosta Grande  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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javimart1212
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Post by javimart1212 »

So, I've had one of these for a while, and while it's not the greatest, it's not the worst. It does provide ample boost, but the idea of rolling back some highs is for me a bad thing. BBE puts it like this:

"A clean boost pedal does nothing but pile on gain, right? Well, some do, but that doesn’t create the experience players want. You see, added gain will push the amp’s front end tubes harder, creating more of the amp’s own harmonics, but that alone will make the amp seem too bright, sacrificing the tonal balance in the process.

You see, we call Boosta Grande a “transparent clean boost” because it doesn’t change the tonal balance of the amp, even with Boosta’s max gain of +20dB slamming those tubes. To achieve a transparent boost experience, Boosta Grande mildly rolls off some top end starting at about 1kHz so that when the amp’s front end is driven harder with gain, the additional upper harmonics generated by the tubes aren’t excessive."

So, is there a way to get an even boost, without rolling off that top end?

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javimart1212
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Post by javimart1212 »

Here's a schematic:
BBE Boosta Grande.png
BBE Boosta Grande.png (10.88 KiB) Viewed 3118 times

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javimart1212
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Post by javimart1212 »

here''s a photo:
bbeboost.jpg

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marshmellow
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Post by marshmellow »

Reduce C6 to 1n.

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javimart1212
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Post by javimart1212 »

Cool, I will try that out. Could you give me a brief explanation of what this mod of c6 is going to do? Thanks for your help.

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javimart1212
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Post by javimart1212 »

Put in the value you suggested and it sounds great. It sounds very, very close to the natural tone; it's just boosted way up. I think this might be the answer to all the bad reviews this pedal receives. :thumbsup

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electrosonic
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Post by electrosonic »

With the 10k resistor and a 5n6 in the op amp feedback loop makes a low pass filter, high frequency cut off is set to 1/( 2*pi* 10x10^3* 5.6x10^-9) = 2.8 kHz

Changing the cap to 1nF moves the cut off frequency to 15.9kHz, so it is now a full range booster

Andrew.

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javimart1212
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Post by javimart1212 »

It is so great to have access to such brilliant people. Thank you all for your help. [smilie=rlp_smilie_242.gif]

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Post by javimart1212 »

So, I dusted this pedal off the other with the intentions of giving it to a friend. I notice that the switch pops when you engage the pedal. Come to think of it, it always did that . I was wondering if anyone has a solution for this? Thanks

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phatt
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Post by phatt »

Try putting a large value bleed off resistor on the *Bypass* leg.
Using the posted schematic, a 1~2 meg to ground off lug 3 or 4 on S1 might help.
Phil.

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Ben N
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Post by Ben N »

If that doesn't work, have a look at this: http://www.muzique.com/lab/led.htm

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