De-smarting the Marshall Uxbridge

tomscii.sig7.se

292 points by fanf2 3 months ago


mysteria - 3 months ago

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.

gavinuhran - 3 months ago

I have this speaker and cannot believe how annoying the smart features are. I'll be talking on the phone in my apartment and the speaker will think I'm trying to prompt it.

"SORRY. YOUR DEVICE IS NOT CONNECTED TO THE INTERNET. PLEASE CHECK YOUR BLUETOOTH SETTINGS AND TRY AGAIN." (at max volume!)

It's unbelievable. I'm not an EE, but would love to know how I can disable these incredible unsmart features.

tlhunter - 3 months ago

Lately I've been wondering if there's a way to do this to Smart TVs. Personally, I like the name "stupify" better ;)

05 - 3 months ago

There’s a project to load OpenWRT onto LinkPlay A31 [0], might be easier than basically replacing the insides..

[0] https://github.com/hn/linkplay-a31

MrBuddyCasino - 3 months ago

This looks an EE‘s approach who hasn’t had a lot of exposure to speaker design. You need to consider Thiele/Small parameters of the chassis, enclosure volume, baffle design and a million other factors to design a proper crossover. You can’t just ltspice your crossover and call it a day. VituixCad would be a more appropriate solution. And then you actually have to measure!

Replacing and amp and „smart“ crap is easy if there is an analogue crossover you can reverse-engineer, if it was just some DSP things get difficult quickly (unless its just a single broadband chassis, but even then…).

And no, you can’t use pre-built „standard“ crossovers or some calculator on a website either.

But other than that, nice that he saved some hardware.

rasz - 3 months ago

>I was delighted, and immediately impressed by the sound quality. The low end was punchy and deep, much deeper than the modest dimensions led me to believe. The high end was crisp and detailed.

Its amazing what a brand name does to ones ears, all of a sudden a small plastic box with SBC Bluetooth codec sounds great.

kazinator - 3 months ago

> I liked it even though the sound reminded me of the “disco smile” (hollowed out mids), but I chalked that up to overly consumer-friendly default EQ settings.

The much simpler explanation is that it has hollowed out mids because it's a Marshall.

309electronics - 3 months ago

Ah the classical Rakoit Linkplay series of modules! I have a arylic up2stream amp that also has one but its the A31 series. Pretty neat to know that its a full Linux computer on a little daughterboard running Linux. Just sad that they dont comply with the Gnu GPL for Uboot and Linux and other Gnu stuff and as an argument have "the multiroom streaming software is quite complicated to integrate reliably". I might get one myself and see if i can do some hacking work and maybe get Openwrt or any other Linux distro on the module with amlogic chip. They seem to be able to be flashed with other firmware because i flashed my Linkplay a31 module instead of arylics software with a tiny openwrt image for the chip which in my case was a Mt7628 so basically a router soc. They seem to use standard Linux and Uboot but with a few custom binaries to handle communication with the dsp-coprocessor on the carier board and a webserver for Management and app control and a custom binary called rootApp that does the magic sauce

munchler - 3 months ago

For those (like me) who are unfamiliar with this device: It looks like a Marshall amp, but is a 9" tall Bluetooth speaker.

Mathnerd314 - 3 months ago

I'm curious about price - sure, the speakers were free ($240 value), but I don't think printing up a PCB is cheap, and those are some pretty big capacitors.

achr2 - 3 months ago

I bought one of these Marshall speakers to use as a practice amp, only to find that the dsp latency is unusably bad. Maybe this is an option…

jimnotgym - 3 months ago

Tangential question, I have a nice audiophile so and no speakers at the moment. I want some speakers for $low that have decent performance. I can build boxes (used to be a carpenter), but need a design and what look like expensive drivers and crossovers. Is DIY speaker construction actually a cheaper way of getting a top notch hifi, or should I just buy second hand?

szundi - 3 months ago

Article suggests that complicated tools are annoying and not right to be that complicated. But one can argue, that if such complexity is actually needed to tackle tasks (like the multiplatform compilation of the Linux Kernel for example), then it is pretty obvious that in the optimal case the learning curve is at least in a linear relationship with the complexity. If given complexity is high enough to surpass the related learning time threshold of the given person then he/she/whatever is going to be annoyed for sure.

There is no escape from this.

amelius - 3 months ago

Why did he replace the class D concept by a more power-hungry and heat-generating class B amplifier?

summeroflove20 - 3 months ago

[dead]

Slava_Propanei - 3 months ago

Removing gay apps from electronics and automobiles.

The future!

mgaunard - 3 months ago

what exactly is the problem with smart speakers? Most people just want to stream Spotify