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Transcript for Audio Amp #HackChat

A event log for Audio Amplifier Hack Chat

Discussing the next step in class D amplifiers :: multi level amplifiers!

lutetiumLutetium 03/31/2017 at 20:180 Comments

Sophi Kravitz so... welcome Jørgen! Let's start!

Jørgen Kragh Jakobsen I am located in Denmark (æøå) Copenhagen - eengineer at startup Merus Audio we do the most advanced class D amplifiers 2x40W and 2x70W with analgo or digitla input

Yann Guidon / YGDES Do they use multiple voltge to save power ?

Jørgen Kragh Jakobsen At nigth time i am tinkering on embedde device and can see that technologi will start to disrupt the way we use to designe audio systems. But let me get back to that later.

Jørgen Kragh Jakobsen http://www.merus-audio.com/images/extranet_download/New_Multi-Level_Class-D_Audio_Amplifier_Supports_Ultra-Compact_and_Low-Power_Applications.pdf

Jørgen Kragh Jakobsen Posted a link by my colleage Rien - You mite need the username and password to get to it - let me know

Yann Guidon / YGDES Ah I remembered reading something about this approach a few years ago :-) You pack enormous power in really tiny spaces so you must avoid dissipating anything :-)

Sophi Kravitz how does that work?

Jørgen Kragh Jakobsen Yes in normal class A and AB you have at least 25% in you device rest goes to speakers

Jørgen Kragh Jakobsen in class D you are down to 5% loss in device

Jørgen Kragh Jakobsen and not a big problem before you start to play party level - normal pcb coolign is ok


Yann Guidon / YGDES What frequency does it use ? are there crazy clock techniques ?

Jørgen Kragh Jakobsen Also for EMC we have some trick to do usign 5 level swithcihg

Yann Guidon / YGDES :-)

Jørgen Kragh Jakobsen we do 300k, 600k or 1200khz

Jørgen Kragh Jakobsen depenting on input level - and how you setup the amplifier profile

Jørgen Kragh Jakobsen Save power and do bether THD

Jørgen Kragh Jakobsen Yes externel filtes is mainly for EMC requiments

Jørgen Kragh Jakobsen

Yann Guidon / YGDES cuuuuute !

Lutetium lol

Jørgen Kragh Jakobsen
This amp can do around 2x40w cont. from a shitty supply

Jørgen Kragh Jakobsen
Analog or digital input

Lucas Coelho Cavalheiro has joined this room.

Yann Guidon / YGDES Oh that would be a perfect fit for restarting my project #Whygeephone :-D

anfractuosity How much does a board like that cost out of interest?

Jørgen Kragh Jakobsen But let get to mika's question

rpstevens What do you think of Gainclone chip amplifiers? I built one a few years ago, seems to work OK.

Edgar What is the frequency range?

Jørgen Kragh Jakobsen Gainclone is old stuff - move on to class

Jørgen Kragh Jakobsen Frequency range is flat upto 20K

Jørgen Kragh Jakobsen http://www.merus-audio.com/images/pdf/extranet_download/MA12070P%20Product%20Datasheet.pdf

Jørgen Kragh Jakobsen Please check the spec in datasheet

Jørgen Kragh Jakobsen back to Mika

Jørgen Kragh Jakobsen You ar not the first to have problem with stagepass or old amp/audio system in general

Jørgen Kragh Jakobsen Get hold of schemaics of the amp/mixer

Yann Guidon / YGDES Are there features in this chip to alter/process/equalize the sound ?

Jørgen Kragh Jakobsen and try to follow the audio path. You need to look for bad caps used or blocking DC between stage in design

EdgaI just started looking at the datasheet, it says low power aplications, but voltage is 18v, how many amps?

Jørgen Kragh Jakobsen or look for noise on supply lines - You need a scope

RRcoder has joined this room.

Jairo has joined this room.

Jørgen Kragh Jakobsen And for Orkhan - every body missing bass ...

Jørgen Kragh Jakobsen yes try do some calculation on input impeaence vs coupling cap - that is now place you could loose base

Jørgen Kragh Jakobsen bass

Yann Guidon / YGDES any information about availability and pricing of small modules ?

Jørgen Kragh Jakobse other places in the speaker and speaker enclouser. You need large volume and good acustic designe to do good bass

thekidtonystark I know I asked this before but since more people are here, is there anyone near miami with scraps they are willingly giving

Jørgen Kragh Jakobsen Our devices is fore high volume prodution - low cost . But I would love to do an exclusive outlet to the fellow hackers.

Edgar What would be the typical application?

Jørgen Kragh Jakobsen We are selling direct to OEM and brands.

Jørgen Kragh Jakobsen Battery powered BT/WIfi speakers

Yann Guidon / YGDES I have another application idea :-P

Jairo Hi all, I'm from Burgos (Spain) I'm building a Class-D amplifier for the final degree proyect

Jørgen Kragh Jakobsen I have arduino library's for setting up our ampliers - not complicated.

Yann Guidon / YGDES oh, does that mean that the amplifier is not a standalone chip ?

Edgar What inputs does it have? Does it support i2s?

Neil Cherry There's a node-red like interface for the Teensy (ARM?)

Jørgen Kragh Jakobsen and for carol : yes we use lots of pie

Carol Willing Is the library open source?

Jørgen Kragh Jakobsen Library will open source yes

Neil Cherry @Carol Willing think so

Carol Willing cool

Neil Cherry oops (orry)

Jørgen Kragh Jakobsen We use Pies for burn in testing - One pie baking 8 amplifers for one month

Jørgen Kragh Jakobsen to do acclerated life time test at max temp -

Neil Cherry Not eating over at you home

Carol Willing Each amplifier has a one month burn in. Wow

Lucas Coelho Cavalheiro Sorry if this is already stated somewhere, but has that demo board passed EMI test in FCC or CE?

Jørgen Kragh Jakobsen we have 3 x 42" racks with 100 amplifiers buring for one month

Edgar can it be configure other ways? like 2 x 40w, 1 x 80w, 4 x 20w?

Carol Willing That's great. I like the max temp test . Good QA.

Jørgen Kragh Jakobsen Yes you set amp up in 4 x single ended, 2x btl or 1x pbtl

Yann Guidon / YGDES niiiice

Jørgen Kragh Jakobsen EMI / EMC passing is end product related

Jørgen Kragh Jakobsen very coupled to how you wire up you speakers ....

Lucas Coelho Cavalheiro I'm aware, but if you demo board passes, it's a good indication that the chip itself operates well withing those specs

Jørgen Kragh Jakobsen and here is our 5 level your friend

Jørgen Kragh Jakobsen Yes your are rigthLucas Coelho Cavalheiro I'm just asking because that could be a selling point for your chip meaning that as long as you make a decent system integration, it will work nice and pass the certification

Jørgen Kragh Jakobsen and we do EMI / EMC testing on modules as well - all good

Lucas Coelho Cavalheiro Just like those small RF modules that you can easily integrate in your product =)

Lucas Coelho Cavalheiro Nice!

Carol Willing Thoughts on when 5 level is preferable to 3 level? Applications?

Lucas Coelho Cavalheiro And by the way, the burn-in test is an awesome reasurance for anyone instersted in using it professionally. Thumbs up!

DonBishop I'm an amateur Electronics Buff and still learning the basics. I'm presently trying to design my own Audio Preamp - ADC Device. Based on the TI INA2137 Audio Differential Line Receiver. I want to make a Mic Pre-Amp and USB interface for Computers. I plan on using the MSP430 Prototyping Boards, that I already have. I have 3 and two of them have the Anaren Wireless Modules on them. I would like to build two different, setups. One Wireless. And one Wired, Sending Audio into the Computer, via USB. To send the Audio into a Computer, for Recording. If this will work. I also bought, LM1085IT-ADJ/NOPB-3A Fixed Adjustable Output Linear Regulator and LM3525M-L/NOPB-Single Port USB Power Switch and Over-current Protection. In case I need to build the whole Circuit from scratch. I don't know if I need to add Resistors to the Circuit or not. Since the INA2137 has some built in. I've spent several weeks. Researching Circuit Designs, for this Chip. But, have only found two, general Designs. On other Web Sites. This one I think, would work best for me. Audio line receiver impedance balancing using a 2nd diff amp, (see hand drawing on this page, http://www.eetimes.com/document.asp?doc_id=1280384&page_number=2). Does anyone have any experience, Designing Circuits with these Chips, that you could share with me?

Thanks,

Don

Jørgen Kragh Jakobsen Yes digital input is I2S - we take 4 audio streams in - and has only volume pr ch and some limiter function on chip

Jørgen Kragh Jakobsen Additionnal audio processing is normal done in DSP

Edgar What would be the minimum voltage? I saw the 250mw ratings for idle, but could it be made into a Pi HAT to do like a portale streaming jukebox?

Jørgen Kragh Jakobsen But time has change and as micro processers is getting faster and get some DSP like instructions

Jørgen Kragh Jakobsen there is no need add a DSP to the party - if you are just to do some bass enhacemnt and speaker EQ

Yann Guidon / YGDES yes, some lifting wavelets work

Lucas Coelho Cavalheiro Jorgen, what would you say that was the most challenging feature or part in the design of the chip that you think you guys are doing better than the competition in the market?Jørgen Kragh Jakobsen My friend ower at ESP32 forum BuddyCasino ported SprieTM's mp3 decoder from the es8266 to esp32

Carol Willing :-)

Kenji Larsen I have a question regarding class D, which as I understand (perhaps incorrectly) uses mosfet switching and PWM. I'm interested in how duty cycle of the switching affects (or doesn't affect) the amp's ability to maintain frequency response across the spectrum. It seems like it can't be completely independent, and also should affect signal to noise ratio... or is it simply that the mosfet switching frequency is so fast that it does not get into the audio spectrum (because, Nyquist)?

Jørgen Kragh Jakobsen I made it stereo and added some DSP - and the ESP32 has still misp to be used.

Jørgen Kragh Jakobsen I think we have a very nice platform to go to very interesting audio applications

Jørgen Kragh Jakobsen starting point woud be Paul Stoffregens Teensy DSP library

Jørgen Kragh Jakobsen lucus : that is our 3 level output stage - and BLT to get 5 level. Dynamic change of modulation base on input level. Nobody does thatLucas Coelho Cavalheiro says:12:59 PM

Nice! I'll look into that to understand a bit more! Thanks!Jørgen Kragh Jakobsen says:12:59 PM

Larsen: Yes switching freq is way above audio - and we have feedback to do very low THDJørgen Kragh Jakobsen says:1:00 PM

For you nerds here is a very deep insight to all the fancy stuff we do on circuit level / ic integration level

Jørgen Kragh Jakobsen http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7707461

Lutetium :)

Carol Willing Awesome! Thx.

Lutetium and please feel free to add more questions here: https://docs.google.com/spreadsheets/d/1xLtoZIUYbqK-UQTdQrp0KaO9QCe_xmDW0N5nyYAN8IY/edit#gid=0

Sophi Kravitz hanks Jørgen!!

RRcoderthanks very interesting chat.

Kenji Larsen Thanks Jørgen! how high does the mosfet switching frequency get? I think you must be making some optimizations since faster state switching means more power consumption...

Jørgen Kragh Jakobsen Please just reach out for me - if you have any audio / class d related question - I am all ways around here

Carol Willing thanks Jørgen for the extra nerd info and a fun chat.

anfractuosity that paper looks nifty, will have a skim of that, not that i'll be able to understand it though, but it's cool to see companies publishing things like that

Orkhan AmirAslan Thanks, Jørgen. It was very informative

Carol Willing Thanks Hackaday too.

Yann Guidon / YGDE That IEEE paper is awesome, I'll love to play with one of these modules !

Jørgen Kragh Jakobsen Larsen - Fast switching gives all kind of trobles - we slow down the speed of mos fet - if not we will do large voltage spikes (inductive load and upto 10 amp and bonding wires ) Dead chips

Kenji Larsen Right - hence my interest in how you solve this? Does this also imply that when an audio amp is processing a higher frequency tone or signal, that the mosfet frequency must similarly be higher, and consume more power? Like, will a Class D playing a constant lower note consume less than when playing a higher note?

Jørgen Kragh Jakobsen I will do what ever I can to set up and outlet. If any one has good connection to Seeed / Sparkfun or Adafruit I will be more then happy to co - build a module

Lucas Coelho Cavalheiro Free samples? Hehe Just kidding... Thank Jorgen and Hackaday! =D

Kenji Larsen Or is the mosfet frequency high enough to be maintained constant regardless of the input signal frequency?

Jørgen Kragh Jakobsen Larsen: Switing frequency not trelated to audio frequency

Kenji Larsen Or do you throttle it to save power if you do have a lower frequency input?

Jørgen Kragh Jakobsen but plaing bass requires more energy the playing high frequency content

Kenji Larsen OK, you keep it independent then

Kenji Larsen Oh interesting about base

Jørgen Kragh Jakobsen We change power modes ( switch freqncy ) base on input level -

Kenji Larsen meaning amplitude?

Jørgen Kragh Jakobsen that is how mutch energy need to be supplied ot load

Jørgen Kragh Jakobsen to load (speaker)

Jørgen Kragh Jakobsen yes amplitude

Kenji Larsen makes a lot of sense. That must dominate the power, of course. I focus too much on the semiconductor properties... Thanks so much, very informative!

Yann Guidon / YGDES Does the EMI/output filter alter THD and stability of the feedback loop ? Is there a "sense" input directly to the loudspeaker coil ?

Jørgen Kragh Jakobsen I will take a break - Thanks for all you interesset - Thanks Sophy - Lets lake some noize later...

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