Audio Systems Hack Chat

We're talking about audio systems and the ICs used to develop these systems in this chat!

Friday, June 2, 2017 12:00 pm PT - Friday, June 2, 2017 12:30 pm PT Local time zone:
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Dafydd Roche joins us in the Hack Chat

Friday, June 2nd at noon PDT, @Dafydd Roche will host the Hack Chat.

Dafydd Roche got into electronics by mistake.

At 18, in an application for a music degree, he mentioned he'd built a few guitar pedals "because it was cheaper". That landed him with a phone call from the electronics department at York University that told him that he was a terrible musician, but that he might excel at Electronics.

19 years later, by night, he continues to dabble with his small business (Expat Audio) whilst becoming increasingly frustrated with laser engravers, 3d printers, pick and place machines and all other forms of manufacturing tools -- because once you've seen how the pro's build millions of a product, you dream of doing the same for the batches of 50 you build!

Dafydd spends his days as the Audio Strategic Marketing Manager at Dialog Semiconductor, arguing with design engineers, doing his best to solve customer problems, and all the other kinds of things that folks caught in the middle between Customers and Design Engineers do at Semiconductor companies.

Dafydd has been a guest on The Amp Hour and has had multiple articles published on audio systems.

We'll be discussing all of these things until time runs out!!

  • Audio Mythbusting
  • Audio signal chains
  • Small business production

Bring your questions! Here's the sheet to guide the discussion.

  • Audio Systems Hack Chat Transcript Pt 2

    Shulie Tornel06/02/2017 at 20:47 0 comments

    Dafydd Roche #betteratelectronicsthanmusic

    audioluxdevices #makemusicwiththeelectronics ;)

    thekidtonystark Thanks.

    Paul Stoffregen do you suppose anyone at Dialog has any interest in prompoting their codecs to the makre/arduino market?

    Yann Guidon / YGDES


    Dafydd Roche I do. I'm the broad market audio dude. Ther'es already an arduino board available with DA7212 on it

    Paul Stoffregen I currently make an udio shield with the STGL5000 chip

    Dafydd Roche

    The ARD-AUDIO-DA7212 is an 'audio shield' that can be used with a number of MCU development platforms due to its compatibility with the Arduino™ R3 pin layout. The audio shield can be used with commercially available development platforms such as Freescale 'Freedom', Intel 'Galileo', Microchip 'chipKIT' and Arduino.

    Read this on Dialog Semiconductor >

    Paul Stoffregen and a growing DSP liibrary to support it

    Dafydd Roche is the SGTL part the old freescale codec?

    Paul Stoffregen

    PJRC Store

    This audio adaptor lets you easily add high quality 16 bit, 44.1 kHz sample rate (CD quality) audio to your projects with Teensy 3.0, 3.1, 3.2, 3.5 or 3.6. It supports stereo headphone and stereo line-level output, and also stereo line-level input or mono microphone input.

    Read this on Pjrc >

    Dafydd Roche do you need linux drivers etc?

    Paul Stoffregen yup, Freescale, or whoever they acquired....

    Dafydd Roche check out DA7219 -- mono in, stereo out... has the 3.5mm jack detection, China/USA headset switch etc all integrated. Stellar drivers.... popular in chromebooks

    Professor Fartsparkle "capless headphone driver" I was wondering why you actually need caps at all, what is the benefift of those design that use chunky caps? (total noob when it comes to audio electronics)

    thekidtonystark #tryteslacoilsformusic

    Dafydd Roche @Professor Fartsparkle oooooh... here we go. that plays to my strengths right here

    Paul Stoffregen the DSP library runs on Teensy, not your PC. It's meant to run "in the background" while yourArduino sketch controlls everything

    Professor Fartsparkle :)

    Dafydd Roche most codecs are single supply. that means that to get a positive and negative swing, you have to DC bias the signal and block the DC from the headphone, or drive the speaker directkly, differentially

    Dafydd Roche two ways to solve the problem. either move your 3.5mm jack GND to be VCC/2 (not a good idea)

    Michele Perla are we talking about DC again? :D (just kidding)

    Dafydd Roche or put in a whopping great big cap in between the chip output and the 3.5mm connector

    Yann Guidon / YGDES the problem with headphones is their common pin....

    Dafydd Roche you need a whopping great big cap, because the low impedance of the headphone (16ohm) creates a high pass filter.

    Paul Stoffregen having now sold many thousands of those shields to makers, I'm thinking a future design will AC couple the headphone outputs. The DC offset "virtual ground" is confusing to many novices

    Dafydd Roche so if you use a small cap, you end up with no bass.

    Dafydd Roche perfect to balance out your beats headphones.

    Michele Perla hahahahaahahahahah

    Professor Fartsparkle ooh that makes sense, I never thought about that

    Yann Guidon / YGDES hahahahaa

    Paul Stoffregen lol

    Professor Fartsparkle heh

    Michele Perla that's screenshot worthy

    Dafydd Roche I am now waiting for my cease and decist from apple ;)

    Professor Fartsparkle lol

    Sophi Kravitz lol hi everyone

    Yann Guidon / YGDES they'll buy your employer and fire you themselves :-P

    Paul Stoffregen looking at the DA7219 datasheet now, fwiw...

    Michele Perla hi @Sophi Kravitz :)

    Dafydd Roche ONLY KIDDING. We owe beats a great deal as an industry, they got everyone to rebuy headphones all over again.

    Yann Guidon / YGDES i Sophi

    Paul Stoffregen heya Sophi

    Yann Guidon / YGDES I'll stay with Senheiser :-P

    Professor Fartsparkle so how does that capless headphone driver work then?

    Benchoff OMG sophi

    Dafydd Roche We use a charge pump to...

    Read more »

  • Audio Systems Hack Chat Transcript Pt1

    Shulie Tornel06/02/2017 at 19:25 0 comments

    Dafydd Roche Paul - that's because the parts (if it's the same as other semi guys) aren't designed, verified, bench tested or prod tested to guarantee drift

    Dafydd Roche drift tests costs seconds on a tester, and in many cases, multi-temp test runs, which costs $$$$$

    Paul Stoffregen in the 90's, I went to see Bob Pease talk once... which was of course 10 minutes of Bob intersperced with 2 hours of National Semi marketing managers

    Dafydd Roche there's a reason why industrial DC converters cost so much. In many cases, the additional test time is one of the reasons

    Michele Perla I think that the best is to leave audio codecs for audio, while using DC specific converters for, well, DC applications

    Paul Stoffregenand he said something that stuck: all datasheets are from the marketing folks, sales pitches to get you to buy the part, pretending it was made for everyone in the world, when in fact they usually designed it for one big client

    Paul Stoffregen do you suppose DC offset could be measured at startup and nulled out?

    Shulie: @Dafydd Roche Thanks for joining us today! Can you please give us a short bio about yourself, your expertise?

    Michele Perla there's temperature drift to account for

    Paul Stoffregen like use an analog switch to disconnect the input signal and short the input to analog ground, and then take a few thousand readings and store the average once it settles?

    Dafydd Roche Hi everyone. My name is Dafydd Roche. I'm a Audio Systems and Strategic Marketing Manager for Dialog Semi. I have 16 years of experience in this game, having worked most of them for TI, and more recently Dialog Semiconductor. I spend my spare time tinkering with Pro Audio products and am one half of Expat Audio, a hobby business making PCB's and modules for Pro Audio guys who want to build up their studio's with DIY gear. At Dialog, I define new audio IC's, I did the same at TI previously. In my spare time, I design, layout, manufacture, pick and place and design enclosured etc for Expat Audio.

    Michele Perla the board may or may not be always at the same temperature

    Michele Perla that's a nice bio indeed @Dafydd Roche :D

    Paul Stoffregen wow, that's some audio IC experience indeed ;)

    Dafydd Roche Paul - You have no idea how many customers I used to answer on our audio converters use in industrial systems.

    Dafydd Roche They would see 130+dB SNR, and want to try and get it at DC... it was a hot mess.

    alusion Is someone from design lab online?

    sfrias1 Hi all. :-)

    Paul Stoffregen yeah, who wouldn't want 21+ bits for cheap!

    sfrias1 :-)

    sfrias1 24 bits A/D converter ?

    Dafydd Roche @Paul Stoffregen The last ADC I worked on at my previous employers integrated the usual PGA, ADC, DSP Core etc... we had an internal request to use it for DC measurements, which our team couldn't commit to, so the other interested party ended up having to make the equivelent circuit from discrete components... at a 15x cost.

    Benchoff @alusion not technically, but we can talk when this is over

    Joshua Reisenauer Do you know much about cabling for audio in large venues?

    alusion @Benchoff okay PM me later, I have some ideas for the virtual/physical hackerspace vision.

    Dafydd Roche @Joshua Reisenauer - some. Mainly from doing live gigs of my own over the years... but nothign "Large" like stadium size. I'd say the biggest issue you'd have in capacitance in teh cabling and ground potential differential between equipment.

    Dafydd Roche I just spotted a question from Brian McEvoy for a cough button for an XLR mic system...

    Dafydd Roche "What do I need in a "cough" button on an XLR mic system to suppress the pop when I press it?"

    sfrias1 Audio cabling in large venues: first, star distributions to reduce audio delay echoes, with replication for multiple edge cells

    Shulie: What is a cough button? :)

    Benchoff "I move away from the mic to breathe in"

    Dafydd Roche You have two potential sources for pop, first is phantom power being quickly charged and discharged through the front end capacitors and secondly, that quick pull...

    Read more »

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