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If you're going through all the effort to design a PCB have you thought about driving the I2S input digitally? I skimmed through the AD85050 datasheet and it ha

If you're going through all the effort to design a PCB have you thought about driving the I2S input digitally? I skimmed through the AD85050 datasheet and it has internal DSP functionality which would have been already tuned for the drivers and box by Marshall. The reason powered boxes sound decent despite their relatively cheap hardware is because of the extensive processing they have in the background to compensate for any hardware defiencies. As the AD85050 has a stereo I2S input there's a possibility for the actual crossover to be either done on the amp chip itself (with the same signal driving both channels) or done on the Amlogic SOC. The latter would be ugly as you would need another DSP chip on your board to do the crossover functionality, or perhaps you could program the AD85050 via I2C to add the appropiate low and high pass filters. A two channel A/D converter would work on the front end, as you could drive both channels with a single analog input to get a stereo I2S out with duplicate channels to drive the amp. A USB input would be much messier if you want true stereo using two speakers unless you plan on doing routing on the software side. With SPDIF you probably could get away with splitting the signal and using a SPDIF to I2S converter chip in each speaker, but you would still need some way to separate out the left and right channels. The AD85050 has mixing functionality via I2C which may help with that. And of course, all this might be more work than desigining an amp in the first place, and it really depends if you want to explore the analog or digital side of things.

bayindirh 2y ago
Marshall speakers, from my experience, has a brand sound signature, and that tuning is not very optimal for every genre of music. Replacing the DSP with a simpler amplifier may allow to get more detailed sound from the drivers and the box themselves and may create a more pleasant listening experience. From what I have seen, the drivers seem pretty full-size for that box, and any disturbing sound characteristic can be tuned with a simple equalizer. A more dynamic approach might create audibly weird sound profile if done wrong. Modern DSPs are magic, but I still prefer an audio pipeline where things show their deficiencies and not hide things real-time.
f1shy 2y ago
> The reason powered boxes sound decent despite their relatively cheap hardware is because of the extensive processing they have in the background to compensate for any hardware defiencies. I will not argue that that could be one ingredient, but a couple of months ago I did a toy for my kids, I bought decent speakers, placed them in a cheap plastic box, and was absolutely amazed bybthe sound quality. The amplifier is a sub 1 dollar class D bought in a Raspberry Pi shop. No processing at all. If the box is sturdy and sealed, and the speaker is good, is incredible what you can do.
- acchow 2y ago
  I'm interested in which speaker and amp those were. Also, the plastic box :)
  - bayindirh 2y ago
    Not the OP, but if you have a little budget, HifiBerry's AMP2 [0] sounds great. After my dad gave his Hi-Fi stack to me (due to having no space at home), I built a small system with this and connected to a set of passive 2.1 Kenwood Hi-Fi speakers for him. They sound amazing, plus HiFiBerry OS is superb for connectivity. I just want to note that software is built with collaboration of Bang & Olufsen. Both hardware and software oozes quality. [0]: https://www.hifiberry.com/shop/boards/dealing-with-blocked-p5-holes-7/ https://www.hifiberry.com/shop/boards/dealing-with-blocked-p...
    - Ringz 2y ago
      The hifiberry documentation is a mess. Let’s say you want to get rid of your Sonos system and start at zero with a Pi (it’s not my first one)… which features could be replaced by hb? What hardware should I buy? Which licenses?
      - bayindirh 2y ago
        I don't have a Sonos system, but I'll try my best to run it down for you. Platform has two starting points: Raspberry Pi + AMPs (or DACs) or Beocrate [0] If you go with the former, you need a Raspberry Pi 4 or 5 (even 2GB models are OK), HiFiberry board of your choice, a case (available from HifBerry), and a PSU in 19-24V range. My setup is as follows: - Kenwood 2.1 passive Hi-Fi speakers. - HifBerry AMP2 - Raspberry Pi 4 / 2GB - Steel case for Raspberry Pi + Board - 20V Meanwell power supply with a barrel jack. If you prefer to use your own amp or powered speakers, there are DACs which you can directly connect to line level inputs. They support the same OS, and some are even support XLR outputs or multichannel I/O for production/studio needs. If you want go all in, you can add a DSP into the mix which allows parametric eqaualization, and room compensation with optional USB Mic (similar to how B&O speakers measure room to self-optimize). Also you can design your own DSP chains and upload to the DSP. Regardless of the OS you run (HifBerry OS or HifiBerry OS64 (which is beta)), you get the following services out of the box: - Roon - AirPlay - Spotify Deamon - Spotify Connect - RadioBrowser & TuneIn support - Squeezelite for Logitech/Squeezebox - Music (for local files) - Bluetooth Spotify daemons require a premium (Spotify) subscription and Roon needs a license/subscription. There are also extensions, but I don't use any of them and don't know what's available. I use the system mostly with MPD to play music from my and dad's personal collections. MPD can also connect to a Samba server. If you have any other questions, I will try my best to answer. Hope this helps. [0]: https://www.hifiberry.com/beocreate/ https://www.hifiberry.com/beocreate/
AstroNoise58 2y ago
I assume you mean AD85050 (rather than AD8255). And yes, the last paragraph before "Going all-in" is about the idea of driving the I2S. But the I2C config sent to the ESMT chip would have had to be reverse-engineered as well...
- mysteria 2y ago
  Fixed, thanks. Somehow the title of the datasheet pdf is AD8255 despite the chip being an AD85050.
zxcvgm 2y ago
I have the same thoughts about the approach, and I'm actually working (on the back burner) a similar thing. It's a harman kardon "smart" speaker with a similar design where the brains are on a separate daughterboard and that's now fried. I've already figured out the control signals and have designed a new daugterboard with an ESP32 to drive the I2S output. I just need to figure out how to downmix the audio to mono and to DSP the L/R channels into tweeter/bass outputs, or to find some code already out there that does this. Any help/pointers here would be appreciated!
- flyinghamster 2y ago
  One thing you might find helpful is to prototype things with GNU Radio and a GRC flowgraph. I'm not sure that would be useful for running on the ESP32, but you could at least tinker around with signal processing tactics that you could implement on it.
j45 2y ago
There’s no shortage of projects on YouTube where people are 3d printing their own speakers, including arranging electronics. Pretty neat for any former car audio heads.

bayindirh 2y ago

Marshall speakers, from my experience, has a brand sound signature, and that tuning is not very optimal for every genre of music. Replacing the DSP with a simpler amplifier may allow to get more detailed sound from the drivers and the box themselves and may create a more pleasant listening experience. From what I have seen, the drivers seem pretty full-size for that box, and any disturbing sound characteristic can be tuned with a simple equalizer. A more dynamic approach might create audibly weird sound profile if done wrong. Modern DSPs are magic, but I still prefer an audio pipeline where things show their deficiencies and not hide things real-time.

f1shy 2y ago

> The reason powered boxes sound decent despite their relatively cheap hardware is because of the extensive processing they have in the background to compensate for any hardware defiencies. I will not argue that that could be one ingredient, but a couple of months ago I did a toy for my kids, I bought decent speakers, placed them in a cheap plastic box, and was absolutely amazed bybthe sound quality. The amplifier is a sub 1 dollar class D bought in a Raspberry Pi shop. No processing at all. If the box is sturdy and sealed, and the speaker is good, is incredible what you can do.

acchow 2y ago
I'm interested in which speaker and amp those were. Also, the plastic box :)
- bayindirh 2y ago
  Not the OP, but if you have a little budget, HifiBerry's AMP2 [0] sounds great. After my dad gave his Hi-Fi stack to me (due to having no space at home), I built a small system with this and connected to a set of passive 2.1 Kenwood Hi-Fi speakers for him. They sound amazing, plus HiFiBerry OS is superb for connectivity. I just want to note that software is built with collaboration of Bang & Olufsen. Both hardware and software oozes quality. [0]: https://www.hifiberry.com/shop/boards/dealing-with-blocked-p5-holes-7/ https://www.hifiberry.com/shop/boards/dealing-with-blocked-p...
  - Ringz 2y ago
    The hifiberry documentation is a mess. Let’s say you want to get rid of your Sonos system and start at zero with a Pi (it’s not my first one)… which features could be replaced by hb? What hardware should I buy? Which licenses?
    - bayindirh 2y ago
      I don't have a Sonos system, but I'll try my best to run it down for you. Platform has two starting points: Raspberry Pi + AMPs (or DACs) or Beocrate [0] If you go with the former, you need a Raspberry Pi 4 or 5 (even 2GB models are OK), HiFiberry board of your choice, a case (available from HifBerry), and a PSU in 19-24V range. My setup is as follows: - Kenwood 2.1 passive Hi-Fi speakers. - HifBerry AMP2 - Raspberry Pi 4 / 2GB - Steel case for Raspberry Pi + Board - 20V Meanwell power supply with a barrel jack. If you prefer to use your own amp or powered speakers, there are DACs which you can directly connect to line level inputs. They support the same OS, and some are even support XLR outputs or multichannel I/O for production/studio needs. If you want go all in, you can add a DSP into the mix which allows parametric eqaualization, and room compensation with optional USB Mic (similar to how B&O speakers measure room to self-optimize). Also you can design your own DSP chains and upload to the DSP. Regardless of the OS you run (HifBerry OS or HifiBerry OS64 (which is beta)), you get the following services out of the box: - Roon - AirPlay - Spotify Deamon - Spotify Connect - RadioBrowser & TuneIn support - Squeezelite for Logitech/Squeezebox - Music (for local files) - Bluetooth Spotify daemons require a premium (Spotify) subscription and Roon needs a license/subscription. There are also extensions, but I don't use any of them and don't know what's available. I use the system mostly with MPD to play music from my and dad's personal collections. MPD can also connect to a Samba server. If you have any other questions, I will try my best to answer. Hope this helps. [0]: https://www.hifiberry.com/beocreate/ https://www.hifiberry.com/beocreate/

AstroNoise58 2y ago

I assume you mean AD85050 (rather than AD8255). And yes, the last paragraph before "Going all-in" is about the idea of driving the I2S. But the I2C config sent to the ESMT chip would have had to be reverse-engineered as well...

mysteria 2y ago
Fixed, thanks. Somehow the title of the datasheet pdf is AD8255 despite the chip being an AD85050.

zxcvgm 2y ago

I have the same thoughts about the approach, and I'm actually working (on the back burner) a similar thing. It's a harman kardon "smart" speaker with a similar design where the brains are on a separate daughterboard and that's now fried. I've already figured out the control signals and have designed a new daugterboard with an ESP32 to drive the I2S output. I just need to figure out how to downmix the audio to mono and to DSP the L/R channels into tweeter/bass outputs, or to find some code already out there that does this. Any help/pointers here would be appreciated!

flyinghamster 2y ago
One thing you might find helpful is to prototype things with GNU Radio and a GRC flowgraph. I'm not sure that would be useful for running on the ESP32, but you could at least tinker around with signal processing tactics that you could implement on it.

j45 2y ago

There’s no shortage of projects on YouTube where people are 3d printing their own speakers, including arranging electronics. Pretty neat for any former car audio heads.