The Amp Hour

Audio DSP with Shannon Parks

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Welcome Shannon Parks of Parks Audio!

  • We haven't had many audio guests selling directly to the consumer.
  • Chris rewatched High Fidelity recently and was spotting Chicago locations.
  • Adam Savage visits Jack White's pressing factory in Detroit (Third Man Records)
  • 2014 recordstore day in Bloomington Illinois
  • "Zoomers"
  • Parks Audio's main product is the Puffin Phono pre-amp
  • Does Shannon have grumpy customers? No more than other industries. But he has been doing product research by emailing with audio people for many many years.
  • Record player cartridge
  • Here are some record equalization standards from the 1930's to 1970's
  • "A lot of engineers think these audio guys are crazy with the terms they use and the snake oil devices. The words might not be correct, but they're talking about real problems they have"
    • "The music sounds thin"
    • "I want more warmth"
    • Warmth is a balance of the lower frequency vs higher frequncy
    • Mastering engineers do this all the time
    • Ben Krasnow needle in the groove
    • Hi Fi sound in the late 50s
    • LPs blew away 78s
    • Edison vs Berliner
    • What is the Puffin and what's inside it?
      • The main element is a Cortex M4
      • Analog front end
        • Pre-amp
        • ADC
        • Power supplies are switchmode above 50 kHz
        • defeatable tone controls
        • Graphic EQ
        • Sliding filters like on Instagram
        • Hagerman site on cartridge impedance and loading. You can't assume it's a flat line.
        • Shannon adjusts for cartridge in DSP.
        • Tooling and testing for DSP was originally done in Matlab
        • Do you visualize the sound input?
        • Using Matlab's FVtool, he can work with Pre-calculated coefficients and see what might happen on the output.
        • Tilt function
        • Talking 3 different coding languages
        • On the most recent update to the code, he started writing in assembly to lower latency, which is a problem for audio products.
        • Doing everything with 64 kB
        • Interrupt based timings
        • Looking at Cortex M7 like on the Teensy 4.0
        • Floats to target FPU
        • Went to fixed point math last year
        • Previous guest Eli Hughes has videos about fixed point math
          • https://youtu.be/bbFBgXndmP0
          • https://youtu.be/7pkXlcapNB4
          • https://youtu.be/SrELHqRqKjo
          • Getting rid of pops and clicks with the "Magic" firmware update being developed for the past year.
          • PDF from early 90s, "record restoration"
          • Working and focusing on a single product
          • Previous product was the "Budgie" - tube phono preamp
            • Lead bending
            • Solder bath
            • Parks Audio is a one person factory (two since his wife helped with Budgie assembly!)
            • Macrofab does the assembly for the Puffin units
            • "I can monkey around with DSP for the rest of my life"
            • Dealing with FBA
            • Steve Ballmer talked about Microsoft working with IBM. It was like "Riding the bear" (try not to fall off)
            • 1000 true fans by Kevin Kelly
            • Responding to email
            • Get in touch!
              • Parks Audio homepage
              • Facebook group
              • Youtube
              • Buy on Amazon
              • Bonus link from Shannon:
                • One more possible link - though previously unmentioned - would be to "Digital Signal Processing Using the ARM Cortex M4" by Donald S. Reay. You were basically asking me how to "Get to Blinky" with DSP, and I focused more on the prototyping tools with Matlab and Python - probably because I end up having many more hours doing that work than writing C code. But Prof Reay's book lays everything out in black and white by using the STM32F407 Discovery board and Wolfson Audio Card to start creating digital filters (both still available). It has actual C code - not snippets but actual files that compile with Keil (free under 32kB) - and walks you through everything. As soon as I started reading it, I knew it would "get me to blinky" and I'd be able to do anything I wanted DSP-wise. It's what I recommend to folks that email me wanting to get into DSP.
                  • Thanks to our Patrons for sponsoring this show! A special thanks to our corporate sponsor, Binho!
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                  The Amp HourBy The Amp Hour (Chris Gammell and David L Jones)
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