Comb Filters & Delay Lines in Software (STM32) - Phil's Lab

Design your own delay-based audio algorithms with FIR comb filters and delay lines! Theory, measurements, and real-world implementation with STM32 MCUs in C. PCBs by PCBWay www.pcbway.com
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[TIMESTAMPS]
00:00 Intro
01:52 PCBWay
02:11 DSP Videos
02:28 Delay Lines
04:19 DSP Hardware
05:15 Delay Line Implementation
09:32 Delay Line Demo
12:01 Delay Line Guitar
12:22 Comb Filter
14:11 Comb Filter Time-Domain
17:19 Comb Filter Frequency-Domain
22:56 Comb Filter Implementation
24:00 Comb Filter Demo
26:10 Comb Filter Varying Gains
27:12 Comb Filter Guitar
28:42 Outro

[@ericmin832]

I wish my professor started each lecture with a sick guitar shred

[@PhilsLab]

Haha same!

[@madrigo]

How glad I am that Phil is doing this DSP series. After building a DDS synth I wanted to dive into DSP. My main problem is that in order to do some physical modeling or filtering I would need to learn more about the models themselves (how the diagrams used for the comb filter is called, where to find more models like that, etc...) and there is not so much information about Z-transforms without involving tons of math. For someone who wants to code a model based on a diagram, that is very unnecessary. Can't wait until Phil makes a video on how to do a Reverb or another more complex model. Cheers for all your work Phil. Cannot thank you enough.

[@PhilsLab]

Thank you for your kind comment! I'm very glad to hear that you're liking these audio-based DSP videos. The next in the series is on IIR comb filters and full digital delays. From that we can work towards a reverb!

[@madrigo]

Hey @@PhilsLab, sorry to bother you but I have two quick questions if you don't mind: 1) If I wanted to refresh all the DSP basics I've learned in college and dive deeper in the audio aspects of it such as effects, synthesis and modeling, do you recommend a course has it all? I wouldn't mind going back to square one and building up from there. 2) What is your audio interface and software? I have an oscilloscope but nothing that is integrated with my PC and capable of bodeplotting. again, thank you so much !

[@PhilsLab]

1) I'd suggest looking at this website www.dspguide.com/ and his book to start off with. A really great, intuitive guide to DSP. Then, for audio-based DSP, look for DAFX by Udo Zoelzer. 2) I'm using a Digilent ADP3450 (USB scope/function gen/..) and a QuantAsylum QA403 for further audio measurements (THD, SNR, ...).

[@madrigo]

​@@PhilsLab Thank you so much!

[@isaacclark9825]

DSP content is my favorite content. Looking forward to the reverb video.

[@PhilsLab]

Thank you, Isaac - glad to hear that!

[@velvetsound]

Me too. The Dattoro algo would be nice.

[@duemilanove1844]

Guitarist Philip 🎉

[@velvetsound]

Thanks Phil. This was EXACTLY the tutorial I needed to finish thinking through my guitar pedal project on real hardware. ❤ This tutorial, plus Will Pirkle’s book, + a little ML model, were the key pieces.

[@PhilsLab]

Awesome, very glad to hear that! Thanks for mentioning Will Pirkle, hadn't heard of him and his books before - will definitely check them out.

[@PCBWay]

Here comes our ROCK'n'ROLL -Phil!

[@santiall73]

Excellent!, I wish it was so easy to find info about actual DSP programming 30 years ago rather than just theory books...

[@PhilsLab]

Thank you!

[@michaelzemah1476]

How did you manage to make the DMA's work with H7 proccessors ?

[@user-mf4di5dz6q]

Sir please make a video tutorial on the Zynq Peta Linux boot process using both QSPI and eMMC as the boot media

[@p_mouse8676]

Thanks for refreshing my memory again, since this has been since I while for me :) Question; Why would you go through the trouble of the second option, while this is basically the same as the first option just with an additional summing block at the end with the original signal as well as the delayed signal? Which is pretty easy to implement on itself.

[@PhilsLab]

Thanks for watching! The FIR comb filter is indeed very simple, but we are building up to the IIR (feedback) comb filter, where then both are incorporated as basic building blocks into delays and reverbs. Essentially, this is just the beginning/a primer and a basic tool for what's to come.

[@velvetsound]

Will we build up to AllPass filters etc?

[@PhilsLab]

@@velvetsound Yes!

[@RafaGmod]

What codec you used?It uses I2S? Got curiousto see the datasheet and what is capable of! I think it would be cool to see a video on how to integrate a CODEC or a high quality DAC on digital boards!

[@isaacclark9825]

Phil covered the design of the board he is using in a past video. Video #88.

[@PhilsLab]

Yeah, as Isaac said I've gone through a (similar) design in previous videos. Codec uses I2S, is a Cirrus Logic CS4270. Not the fanciest of codecs but very easy to integrate and set-up!

[@dwagner6]

Gotta ask again - what do you use for your slides? LaTeX/Beamer?

[@PhilsLab]

Used to go the LaTeX route, but now it's PowerPoint + drawings/equations using draw.io (with mathematical typesetting).

[@tobix4374]

This is so cool!

[@PhilsLab]

Thanks, Tobi!

[@kavtech_midi]

please make series dsp build, espesially for guitar multi effect, this is so great...👍

[@PhilsLab]

Thank you - more to come! :)

[@josbouten]

How is the opamp U400A biased at half the supply voltage if there is only R406 to +VREF and no resistor to GND ?

[@PhilsLab]

+VREF is at half the supply voltage, generated by a potential divider in this case. The op-amps are low input bias-current FET types, so there isn't a large voltage drop across the bias resistor.

[@tamaseduard5145]

👍🙏❤