What's Inside the Mono Synth Pedal? ⚡🎹🎸

[@erikvincent5846]

From what I was able to gather from your video, this is what I am guessing. Firstly, the MCP6002 sounds familiar because that is a common opamp that is used when dealing with 3.3V microcontrollers and microprocessors when dealing with input traditionally in the realm of 9V systems. You may have remembered it from the Raspberry Pi Pedal at Electrosmash, which is actually how I discovered this channel. So, topology wise, here is what I am guessing. Two of the multiple opamps (and if I was a betting man, the MCP6002), are simply used as input and output buffers to keep impedance low. From the input buffer of the opamp, the ADC takes over the signal and takes that amplified signal and spits out the data on the SPI line, which I am going to guess will be SPI0 on the Blackfin. On the Blackfin's other SPI bus, SPI1 (or maybe SP0 for this and SPI for the ADC, whichever the board layout was better for, I'd guess), the NV Flash holds settings, and possibly even a binary (kind of like the Spin FV-1 holds stuff in its EEPROM). Obviously, the Blackfin is where the "black magic" happens, in which it does have a good amount of RAM to do things with, so long as the programs are ASM based. Then it spits out on its I2S bus its processed audio data to the DAC, which then probably goes out to the out buffer opamp, and that covers the general topology. The additional opamps could be for different things, like gyrator circuits for band EQ, analog oscillators, comparators, or any number of things that can be tasked to them. One of them is probably the "adder" circuit for blending the signals.However, this is also all best guess. Basically, if you gave me these components and told me to setup a pedal, that's how I'd tackle it. I am going to guess the headers for debugging are either the UART or its JTAG (some STM32's can be programmed with a much lower pin count than a typical JTAG contains).Anyways, awesome channel, great positive attitude and I look forward to seeing more.

[@BlitzCityDIY]

aha! that is definitely where I had heard of the MCP6002 before and thank you for this wonderful signal flow hypothesis/synopsis!

[@erikvincent5846]

@@BlitzCityDIY No prob.

[@pinealservo]

Sounds pretty likely to me, except that the 10-bit ADC is probably for reading all the control pots. The AKM Codec is going to provide the ADC for the signal input as well as the DAC for the signal output. I may have used that exact AKM part before in some embedded audio application or other; it'll be communicating with the Blackfin DSP over some variant of I2S as you say. I worked more or the firmware side of things, so I can't say much about your analysis of the analog bits except that it sounds plausible. :) I used to work for the part of Harman that was originally DoD Electronics, one time maker of fine guitar pedals. The corporate overlords shut down the local office, and I now have as souvenirs some interesting test equipment and prototype audio gear from earlier days; it's pretty fascinating stuff to look at and play with, although very obsolete now!

[@erikvincent5846]

That makes sense with the ADC, totally missed that. DOD, eh? I made a modded clone of the DOD Thrash Master I traced a bit ago in EAGLE that I really dug. Have any stories of the DOD years? Like the whole using a CD4007 as a bypassing switch?

[@smarkalet9078]

Very cool! The trick to get the knobs off is to slip a shoelace or something underneath and get a good grip on the string to pull up.

[@BlitzCityDIY]

thanks! I will try that

[@PCB-]

I second the shoelace trick, works great. I learned it when I was repairing a modern Electro-Harmonix pedal as well.

[@videoaccount5676]

Your picture should be next to the definition of cool in the dictionary

[@BlitzCityDIY]

😺 thanks!

[@jimjay8828]

Great teardown and extra + for the sharp image and awesome lighting

[@BlitzCityDIY]

thank you very much!

[@TravisHardiman]

it sounds like a dang midi file, I love it!

[@BlitzCityDIY]

right?! the tone is crazy

[@郭子勋]

I’m a guitarist + EE engineer. This vid is just AWESOME!

[@thramkammarat]

More of this!!!

[@BlitzCityDIY]

noted!

[@juandelacal8343]

Well done!!! You rocks!!!

[@ratmadness4858]

turns the sound into numbers, jacks with the numbers in the DSP and sends them to the DAC

[@SalvagedCircuitry]

Yaasss! Teardowns are the best! Those knobs are probably just pressed on. The best way to pop them off is to use a plastic spudger or an old plastic giftcard and pry gently from underneath. This way they won't get scratched up. Yes I'm talkin' bout those silly promotional gftcards you get in the mail :D. Also, your suggestion of a single sided PCB is very likely. Nice job liz :D

[@BlitzCityDIY]

Thank you! And that's a good tip- I was going right for some pliers and I was like "whoa self, chill out" haha

[@erikvincent5846]

@@BlitzCityDIY you might be able to use a decently sized flat head. That's been my trick with pedals I have had to tear apart for repair.

[@curtiswright4809]

can you see what d2 (diode 2) next to the 9v power in is. I assume its the same as d11. I fried mine tonight with a 9v 1000ma power daisy chained so be aware of this pedal does not like over ampage, btw there nothing of note on the other side just leave it.

[@erikvincent5846]

Would I be able to send a PCB pedal kit to you?

[@NiHaoMike64]

Nice Laura Kampf logo in the background.

[@BlitzCityDIY]

Her videos are my favorite

[@alexstone691]

Wow first for the first time