2.1 amp with DSP -- preview/teaser

[neildavis]

This is a Speaker Building Design Team project, so it will get a very detailed write-up. But it's finally working and I'm kind of excited by it, so I thought a preview was in order.

The amp is actually 6 channels: two for the subwoofers, and two for each woofer and tweeter. The crossovers are all done in the ADAU1701 DSP board (the green board in the second picture). You can select from 6 different crossover types and 7 frequencies using your Android cell phone. Both the woofer-tweeter and sub-woofer crossovers are customizable. The cell phone doesn't photograph well, but you can sort of make out the display in the last picture. Press the crossover button to select the next crossover in the list, or press and hold to go backward.

But what's really cool is that Dayton WFA02 wifi adapter. You can play FLAC files from your phone or switch to Spotify or other online sources--it's nice.

The plate amp is built from a 1/4" aluminum panel. I removed the fan from the Sure amp and mounted the amp upside down, with a thermal pad to transfer heat to the panel. The back of the plate amp in the third picture is actually for a second version of the plate amp that is designed to replace an SD100 amp.

Fun project but it has taken a long time to mount the parts, build cables and wire up the components. Very tedious. And lots (and lots) of software!

As I said, there are two versions of this project. The second one has a very interesting tweeter arrangement with a passive crossover at 5000Hz. Hint: what tweeters remind you of zebrawood?

[bcodemz]

Wow! That is really cool. This is what a lot of people probably would want, everything integrated in one box, easy to use, wireless. Just fantastic. I'm going to be working towards that as well, but I don't see mine finished for another year or so.

[scottvalentin]

Fantastic!!! Can't wait to see the details.

[ani_101]

Very nice. Looking forward to seeing the write-up

[ernperkins]

Very exciting Neil! Anxiously awaiting the details!

[wogg]

Excellent! A fancier version of my analog active crossover 2.1 plate amp. I'm much better at whipping up op-amp circuits than programming DSP.

Looking forward to details on this one.

[Sydney]

... You can select from 6 different crossover types and 7 frequencies using your Android cell phone. Both the woofer-tweeter and sub-woofer crossovers are customizable. ...

The capabilities allowed by manipulating parameters are intriguing.
Presumable an optical feed directly from a CD player is an option?
As well as signal taps that bypass on-board amps ( with external amplification in mind ).

[donradick]

Pretty darn incredible!
Hope that PE makes a product out of this.

[tomzarbo]

Ha! I thought I was hot stuff with my little "Micro-B" 2.1 mini plate amp. This thing is about 1,000 times more complicated and so much more incredible.
Wow. I just hope I'm smart enough to understand most of the write-up!
If it had a few decals and a Dayton Audio logo it could be a product PE would sell!

Amazing work sir!

TomZ

[djkest]

This is a very cool project. I am interested in this Wifi Adapter!

[thekorvers]

Wow. Impressive! I am looking forward to more details.

[Kevin K.]

Super Cool Neil!

[augerpro]

Neil, any chance the DSP would be available standalone?

[neildavis]

Thanks all.

This is actually a preview of "Act 4" and there was supposed to be 2 other write-ups before it: Act 2 and Act 3. Act 1 was just the subwoofer, which I already wrote up. The 4 acts make a "Play"-- and this was my version of the Sonos Play series of active WiFi speakers.

Here's some more info on the WiFi module:

The WiFi wasn't supposed to appear until Act 4, but I wanted to jump ahead and get a closer look at that WFA02 adapter. The more I play with it the more I like it. I know PE doesn't like it when people divulge the manufacturer of their products, but the vendor isn't very well hidden. If you look at the properties when you cast to it, it says "Linkplay Technology, MUZO Cobblestone". PE did a good job of branding the case and their cell phone app with their own logo, but there are quite a few places where the Linkplay name shows up. This is worth knowing because a device like this needs good support, and the fact that many companies are building products with the Linkplay modules and that it has been integrated with Amazon's Alexa are signs of good long-term support. Also, the current Muzo app works fine with the Dayton module, and that app was just updated last month to add another music service. Support is good.

The module seems to work very well playing music from the cell phone or when cast using DLNA. It will play all of your library files at full resolution, plus it has a number of online cloud-based services to choose from. The selection of services is not as good as Sonos or Heos (no native integration with Pandora or SiriusXM), but at least the list has been growing. I haven't experimented much with the multi-room feature, but that capability looks very promising. Each module has a built-in access point that implements mesh routing, so it can route the signal with minimal delay to multiple modules. That solves the synchronization problem for separate left or right modules, and it makes the system very scalable so you can route any audio to any room.

One challenge with WiFi audio is that volume control must be done through the receiver module. So if you are playing your computer through the module, you will need to keep your cell phone handy to adjust the volume. Fortunately, the WFA02 module has an analog input where you can plug in your computer audio so you can adjust the volume from the computer. It's great for non-critical listening and most computer audio. For high quality listening you just cast to the module or let the module play a shared music library on your computer or else play the music stored on your cell phone. It's great to have these different options for selecting different sources and for routing the audio to different destinations (if you have more than one WFA02 module).

The WFA02 uses a little self-adhesive patch antenna on the inside of the case, but it is connected to the board with a standard IFL connector. So adding an external antenna is fairly simple, although it will certainly void the warranty to do that. I bought an IFL/SMA cable to install the antenna on the plate.

At $38 this module is a steal. Although other vendors are selling the Linkplay modules, nobody is offering this module at this price. And the amount of technology packed in this $38 box is absolutely astonishing. The technology works as advertised and is well supported. I'll provide some hookup details in the write-up, but it's really very simple.

[neildavis]

Neil, any chance the DSP would be available standalone?

Yes, but they are hard to make and I'm not going to built any more of this version. However, there will be a new version that will be easier to assemble. This board is basically the Analog Devices reference circuit that is used in the miniDSP, with some additional circuitry: a switching regulator, an extra stereo DAC, an Arduino CPU module and an FTDI USB-serial interface for communicating with a PC. All of that extra circuitry adds costs and takes a long time to assemble. The new version will extend the "module" approach that worked well with the Arduino CPU. The switching regulator will get replaced by one of those LM2596 buck converters available for $2 each on eBay. The FTDI USB gets replaced by a module, and there will be a place to solder in a HC06 Bluetooth module as well. And the DAC circuitry gets replaced by a $5 PCM5102 DAC module. These modules require a somewhat larger board, but they reduce the amount of soldering/assembly by about a factor of 2.

I started laying out the new board, but it still has a long way to go and it hasn't been a high priority. Once I get these speakers done and the write-ups completed I'll get back to that board. The new board should be easy enough to assemble that I might make a few to sell.