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Baltimore Sonic Research Institute Radical Conversion Discrete Opamp Distortion

Baltimore Sonic Research Institute Radical Conversion Discrete Opamp Distortion

by Baltimore Sonic Research Institute
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In the depths of the Covid-19 pandemic, when everyone was stuck at home making sourdough and wiping down groceries with Clorox and picking up new hobbies out of boredom, I spent a couple months tracing and building clones of all the analog Boss distortion pedals in my collection. I wanted to pick them all apart and see what made them do what they do while also doing many hours of relaxing PCB design work and a whole lot of soldering. What came out of that project was a deep interest in simple discrete opamps like the architecture Boss has used in roughly a dozen different products starting with the OD-2 in 1985. It has appeared in hits like the BD-2, OD-3, and FZ-2, as well as more obscure cult classics like the MZ-2, PW-2 and MD-2. It is one of the fascinating elements that has tied a wide range of disparate Boss products together over the last 40 years.

Radical Conversion uses multiple discrete opamp architectures, including the classic Boss-design, to create a completely discrete, 27-transistor alternate universe homage to the Metal Zone, including the semi-parametric active EQ circuit. The titular Radical Conversion from integrated circuits to discrete opamps started primarily as a flex, because its crazy to make a discrete Metal Zone, but also because it sounds really good to create harmonically-rich drive sounds with lower performance opamp designs. All the subcircuits and filtering have been fine tuned for modern preferences and Radical Conversion adds a trio of preamp voicings to shape the overall voice of the pedal.

Volume - Sets the output volume of the pedal. Crank this one up.

Gain - Sets the amount of distortion in the primary gain stage. EVERYTHING in this design is contributing harmonic complexity, but this control sets the overall saturation level.

Preamp voicing (toggle)
I - The traditional MT-2 preamp voicing adds a cutting midrange boost before the primary gain stage. Often disabled in popular mods, this boost is the classic midrange snarl and works really well for adding pseudo cocked wah edge to riffs and leads. You’ll hear it mostly on the plain strings.
II - Tight preamp boost for a razor sharp low end response in the gain stage. Excellent for players in low tunings who don’t want any flub.
III - Fat preamp boost feeds more low end into the gain stage for added compression. Beef up single coils or a bright guitar or really lay into the riffs for sludgier tones

Bass - Peaking low end boost/cut

Treble - Shelving treble boost/cut

Mid Freq - Semi-parametric frequency control for the midrange band. CCW is lower mids down to ~200 Hz and CW is higher mids up to around 4K Hz

Mid Gain - Boost/cut control for the semi-parametric mid band

Activate - True bypass soft-click footswitch to turn the effect on and off

Power supply - Always use a high quality regulated 9V DC negative tip power supply with your BSRI Audio pedal.

Many thanks to Dr. John Snyder of Electronic Audio Experiments for his encouragement and for pointing me in the right direction a couple times in this project. Without his advice, I probably wouldn’t have solved a key design problem in making the more current-hungry active filter stages work.

Warranty & Returns

All New products are covered by the manufacturers new warranty. Please check their website for the length of warranty and warranty conditions. If an item you receive is faulty get in touch with us ASAP. Second Hand products come with a 4 week warranty from us. If there is an issue let us know ASAP! This covers normal use and does not cover accidental damage, misuse, wrong power plugged into it, modding, water damage or any other damage caused by mistreatment. Just treat it nice and all will be good!

Shipping

We send A LOT of packages every week so don't worry about the shipping side of things!

We've never lost a thing and your awesome new gear will be packed up really well to avoid any damage in transit.

If your order comes in before 2pm we will ship it same day. Most of the time we pack things up all the way to 4pm so just call if you need it to leave same day after 2pm.

We ship mainly with Australia Post but may use a courier depending on location and size of the package.

Free Post ships with Australia Post standard and expected shipping times are between 4-6 business days depending on location. It will be longer to outside of metro and rural areas.

Express Post will usually be with you next business day in metro areas of QLD, NSW, SA, VIC and TAS. WA will take 2 days to metro and extra days after that to out side metro and rural areas.

Everything we ship has a tracking number with the exception of some power cables and smaller envelope packages. You will be emailed tracking once your order has been shipped!

Videos

In the depths of the Covid-19 pandemic, when everyone was stuck at home making sourdough and wiping down groceries with Clorox and picking up new hobbies out of boredom, I spent a couple months tracing and building clones of all the analog Boss distortion pedals in my collection. I wanted to pick them all apart and see what made them do what they do while also doing many hours of relaxing PCB design work and a whole lot of soldering. What came out of that project was a deep interest in simple discrete opamps like the architecture Boss has used in roughly a dozen different products starting with the OD-2 in 1985. It has appeared in hits like the BD-2, OD-3, and FZ-2, as well as more obscure cult classics like the MZ-2, PW-2 and MD-2. It is one of the fascinating elements that has tied a wide range of disparate Boss products together over the last 40 years.

Radical Conversion uses multiple discrete opamp architectures, including the classic Boss-design, to create a completely discrete, 27-transistor alternate universe homage to the Metal Zone, including the semi-parametric active EQ circuit. The titular Radical Conversion from integrated circuits to discrete opamps started primarily as a flex, because its crazy to make a discrete Metal Zone, but also because it sounds really good to create harmonically-rich drive sounds with lower performance opamp designs. All the subcircuits and filtering have been fine tuned for modern preferences and Radical Conversion adds a trio of preamp voicings to shape the overall voice of the pedal.

Volume - Sets the output volume of the pedal. Crank this one up.

Gain - Sets the amount of distortion in the primary gain stage. EVERYTHING in this design is contributing harmonic complexity, but this control sets the overall saturation level.

Preamp voicing (toggle)
I - The traditional MT-2 preamp voicing adds a cutting midrange boost before the primary gain stage. Often disabled in popular mods, this boost is the classic midrange snarl and works really well for adding pseudo cocked wah edge to riffs and leads. You’ll hear it mostly on the plain strings.
II - Tight preamp boost for a razor sharp low end response in the gain stage. Excellent for players in low tunings who don’t want any flub.
III - Fat preamp boost feeds more low end into the gain stage for added compression. Beef up single coils or a bright guitar or really lay into the riffs for sludgier tones

Bass - Peaking low end boost/cut

Treble - Shelving treble boost/cut

Mid Freq - Semi-parametric frequency control for the midrange band. CCW is lower mids down to ~200 Hz and CW is higher mids up to around 4K Hz

Mid Gain - Boost/cut control for the semi-parametric mid band

Activate - True bypass soft-click footswitch to turn the effect on and off

Power supply - Always use a high quality regulated 9V DC negative tip power supply with your BSRI Audio pedal.

Many thanks to Dr. John Snyder of Electronic Audio Experiments for his encouragement and for pointing me in the right direction a couple times in this project. Without his advice, I probably wouldn’t have solved a key design problem in making the more current-hungry active filter stages work.

Warranty & Returns

All New products are covered by the manufacturers new warranty. Please check their website for the length of warranty and warranty conditions. If an item you receive is faulty get in touch with us ASAP. Second Hand products come with a 4 week warranty from us. If there is an issue let us know ASAP! This covers normal use and does not cover accidental damage, misuse, wrong power plugged into it, modding, water damage or any other damage caused by mistreatment. Just treat it nice and all will be good!

Shipping

We send A LOT of packages every week so don't worry about the shipping side of things!

We've never lost a thing and your awesome new gear will be packed up really well to avoid any damage in transit.

If your order comes in before 2pm we will ship it same day. Most of the time we pack things up all the way to 4pm so just call if you need it to leave same day after 2pm.

We ship mainly with Australia Post but may use a courier depending on location and size of the package.

Free Post ships with Australia Post standard and expected shipping times are between 4-6 business days depending on location. It will be longer to outside of metro and rural areas.

Express Post will usually be with you next business day in metro areas of QLD, NSW, SA, VIC and TAS. WA will take 2 days to metro and extra days after that to out side metro and rural areas.

Everything we ship has a tracking number with the exception of some power cables and smaller envelope packages. You will be emailed tracking once your order has been shipped!

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