Chuck D. Bones
Circuit Wizard
The production version is known as the Black Country Customs TI Boost. As endorsed by Tony Iommi.
The TI Boost is a slightly modded TC Electronics Spark Boost. I breadboarded a stock version, then started stripping out unnecessary parts, fiddling a few component values, and here's the result. I did not try to match the Dark Esbat ref des; too many changes.
The 1st stage in the TCE Spark Boost & BCC TI Boost is a 32KHz 2nd-order low-pass filter. My philosophy is "why use 10 parts when 2 will do?" so I ditched the 1st stage. R2 & C2 provide all the input filtering we need. We also don't need a Vref buffer, so that's another opamp gone. TCE uses the OPA2134. That's a very good FET-input dual opamp. BCC uses the MC33178, which is a good BJT dual opamp. I went with the good ol' TL072. Any of them will work in this circuit. The MID switch selects between a 10dB bump at 500Hz, a 9dB bump at 800Hz or a flat freq response in what is now the 1st stage. These mid bumps are broad and create a strong mid presence. Not satisfied with the Flat setting, I added R6 & C6 which make a 4dB bump at 1KHz when the MID switch is in the middle position. I wanted more available gain, so I changed the DRIVE pot to C250K, increased R10 to 220K and reduced C8 to 47pF. C7 does not need to be 10uF, 1uF lets plenty of bass thru. I got rid of the coupling caps before and after the VOLUME pot and returned pin 1 of the VOLUME pot to Vref. To avoid disturbing Vref, I increased R11 to 10K and the VOLUME pot to A100K. The original VOLUME pot was B-taper, more on that later. When DRIVE is dialed-down for clean boost, the output level barely gets above 1Vp-p. To fix that, I increased the gain of the 3rd stage by 11dB. Since the VOLUME control is ahead of the 3rd stage, we can always back off on VOLUME if we crank DRIVE in order to avoid overdriving the last two stages. If you always dime DRIVE, then there is no need to increase the gain of the 3rd stage. C11 does not need to be 10uF, so I replaced it with a 2.2uF film. I also tried 1uF and jumpering C11. They all worked well. With C1 jumpered, the output might scratch a tiny bit when turning the BASS pot, so I opted to keep C11. The tone stack and last stage are unchanged ,except for increasing R19 from 100Ω to 1K for better protection of the last stage. Because Vref is no longer buffered, I reduced the impedance of the Vref divider (R21, R22 & C17). This modded version does everything the Esbat does, but has more gain available, higher output available and a lot fewer parts. Don't get me wrong, the Dark Esbat & Spark Boost are great pedals. Depending on how you intend to use this pedal, B-taper might have a better feel for the VOLUME pot. With the increased gain in the 3rd stage, A-taper is recommended. If you like to dime DRIVE, then keep the 3rd stage gain at or near stock. For extra output, run this pedal at 18V. Make sure you use 25V or higher electrolytic caps.
A reminder - this pedal does not make Tony's Black Sabbath tone on it's own. You have to use it to overdrive an amp or amp emulator. Rock On!
L-R: VOLUME - TREBLE - BASS - DRIVE - MIDS
The TI Boost is a slightly modded TC Electronics Spark Boost. I breadboarded a stock version, then started stripping out unnecessary parts, fiddling a few component values, and here's the result. I did not try to match the Dark Esbat ref des; too many changes.
The 1st stage in the TCE Spark Boost & BCC TI Boost is a 32KHz 2nd-order low-pass filter. My philosophy is "why use 10 parts when 2 will do?" so I ditched the 1st stage. R2 & C2 provide all the input filtering we need. We also don't need a Vref buffer, so that's another opamp gone. TCE uses the OPA2134. That's a very good FET-input dual opamp. BCC uses the MC33178, which is a good BJT dual opamp. I went with the good ol' TL072. Any of them will work in this circuit. The MID switch selects between a 10dB bump at 500Hz, a 9dB bump at 800Hz or a flat freq response in what is now the 1st stage. These mid bumps are broad and create a strong mid presence. Not satisfied with the Flat setting, I added R6 & C6 which make a 4dB bump at 1KHz when the MID switch is in the middle position. I wanted more available gain, so I changed the DRIVE pot to C250K, increased R10 to 220K and reduced C8 to 47pF. C7 does not need to be 10uF, 1uF lets plenty of bass thru. I got rid of the coupling caps before and after the VOLUME pot and returned pin 1 of the VOLUME pot to Vref. To avoid disturbing Vref, I increased R11 to 10K and the VOLUME pot to A100K. The original VOLUME pot was B-taper, more on that later. When DRIVE is dialed-down for clean boost, the output level barely gets above 1Vp-p. To fix that, I increased the gain of the 3rd stage by 11dB. Since the VOLUME control is ahead of the 3rd stage, we can always back off on VOLUME if we crank DRIVE in order to avoid overdriving the last two stages. If you always dime DRIVE, then there is no need to increase the gain of the 3rd stage. C11 does not need to be 10uF, so I replaced it with a 2.2uF film. I also tried 1uF and jumpering C11. They all worked well. With C1 jumpered, the output might scratch a tiny bit when turning the BASS pot, so I opted to keep C11. The tone stack and last stage are unchanged ,except for increasing R19 from 100Ω to 1K for better protection of the last stage. Because Vref is no longer buffered, I reduced the impedance of the Vref divider (R21, R22 & C17). This modded version does everything the Esbat does, but has more gain available, higher output available and a lot fewer parts. Don't get me wrong, the Dark Esbat & Spark Boost are great pedals. Depending on how you intend to use this pedal, B-taper might have a better feel for the VOLUME pot. With the increased gain in the 3rd stage, A-taper is recommended. If you like to dime DRIVE, then keep the 3rd stage gain at or near stock. For extra output, run this pedal at 18V. Make sure you use 25V or higher electrolytic caps.
A reminder - this pedal does not make Tony's Black Sabbath tone on it's own. You have to use it to overdrive an amp or amp emulator. Rock On!
L-R: VOLUME - TREBLE - BASS - DRIVE - MIDS
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