A Streaming HiFI Power AMP based on RasPi MPD (Rune/Volumio) Projects - Page 1
Forum section: electronics / projects

author: brentsinger
author_rank: Newbie
timestamp: May 13, 2015, 08:01:55 am
content: Hi people.I have wanted for a while to build a big arse Class D power amp based on the TAS5624. This is a pretty good part that'll put 120W into 8ohms with 0.02 THD. My plan is to put two of the 5624's with a modulator part (TAS5558) and a MCU. The MCU does house keeping, USB Audio Device, mux's the input sources (RasPi, Generic I2S, and USB). The RasPi input would be I2S. The Amp section of the design is a close copy of the TAS5624 Reference board by TIhttp://www.ti.com/tool/tas5624addvevm. I've already lashed up a RasPi to the reference board and it works really well, sounds clear (no actual measurements yet though.) No analog in the system at all - until the final H bridge power stage drives the loud speaker.The goal is a system like a Sonos, uber cheap, for DIY Hifi or anyone who needs a new amp. So you could use your old speakers, or find some new free standing cabinets, etc, and then hack this board into them. You could build your own speaker cabinets with this board burried inside, and then control it over Wifi.I've finished at the schematic level and I've done a component placement. I've put detailed details here:http://www.runeaudio.com/forum/post6737.html#p6737,I won't repeat the details.I want to kick start it and aim for 50 buyers @ $400 a piece. The markup is a standard 70%, and 1/2 the net revenue is going to be donated to the Rune and Volumio guys for making the streaming projects happen. The project files will go FreeBSD open source after the kickstarter, and the MPD/Rune/Volumio stuff is open source already.Am I pissing into the wind? Will this work?

author: technix
author_rank: Super Contributor
timestamp: May 13, 2015, 08:20:34 am
content: Quote from: brentsinger on May 13, 2015, 08:01:55 amJust saying, you can absorb the Cirrus Logic Pi Audio Card design into yours so the WM5102 can do the audio path switching for you, and provide you with high quality low power analog IO. The remaining unused I2S interface from WM5102 can be used to drive your existing circuitry. This will make your board essentially a high end audio amp.

author: brentsinger
author_rank: Newbie
timestamp: May 13, 2015, 11:37:05 pm
content: So r u saying that I need an analog input? What about wm8731 - cheap simple and I have code already.Is there something more special about the cirrus chip?Thanks for reply

author: moffy
author_rank: Super Contributor
timestamp: May 13, 2015, 11:49:58 pm
content: Sounds like a great idea. I do agree though that an analogue input would be an advantage because of its ubiquitous nature. I have lashed up a RasPi to a stereo DAC, WIFI router, HDD and Volumio for a wireless controlled HIFI system. Works very well. Best of luck.

author: technix
author_rank: Super Contributor
timestamp: May 14, 2015, 12:19:54 am
content: Quote from: brentsinger on May 13, 2015, 11:37:05 pmThe analog input can be used when you want to plug your iPod to this amp: the WM5102 can switch the signal path from line in to AIF2 I2S to your amp for you. The analog output is for whenever you want to plug a headphone in and switch the entire power amplifier section off.WM5102 have very good audio performance and quality and the entire Cirrus Logic Audio Card have existing ALSA-based kernel drivers for Raspberry Pi.Cirrus Logic Audio Card is exactly Wolfson Audio Card for Pi but came in the HAT form factor.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 14, 2015, 06:39:45 am
content: It's a bit silly to use analog line in for music when you could just plug the USB into the Pi and keep it digital all the way. (Though it can still come in handy for use with apps.) Headphone out can be nice to have for some applications.

author: brentsinger
author_rank: Newbie
timestamp: May 14, 2015, 06:53:17 am
content: True but iPhone,? No usb. Perhaps legacy home theatre stuff too like DVD player? Xbox?

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 14, 2015, 07:00:07 am
content: Every iPhone I know of has USB, not to mention WiFi. Any decent DVD player has S/PDIF out, same with the Xbox.Analog audio really is the VGA of the audio world. Still useful and common, but considered a last resort when dealing with digital amplifiers. What would be interesting is a true dual mode digital amplifier that can operate as either a pure digital or "hybrid digital" with the same output stage. And not a pure digital with an ADC strapped on or a hybrid digital with a DAC strapped on like all of the "dual mode" amplifiers I have seen.

author: technix
author_rank: Super Contributor
timestamp: May 14, 2015, 07:32:38 am
content: Quote from: NiHaoMike on May 14, 2015, 07:00:07 amUse USB of iPhones or any other Apple gear requires either a MFi license or a lot of black box hacking. For us hobbyists the former is pure fantasy and the latter not only involves computer trickery but also is legally ambiguous. AirPlay works though and that requires just running shairport-sync (which is a black box reimplementation of Apple's AirPlay protocol) on the Pi and it sends audio down ALSA into I2S of the Pi.Cirrus Logic Audio Card contains WM8804, a SPDIF to I2S transceiver and you just need to keep that intact, attached to one of the AIF of WM5102.

author: brentsinger
author_rank: Newbie
timestamp: May 15, 2015, 10:19:32 pm
content: I think that the Cirrus logic card is for a different job. It's for recording or DSP tricks inside the PI. I'm not sure it is a goal of my system to allow these things. I'm trying to build a streaming network player with a few bolt ons (to be practical) and I have to be careful to avoid making it a Christmas Tree, i.e. hanging everything off it that I can. Also, that card is $32!! There's no way I could put those parts on my board for +$32...So the best way to fly is to put down a separate connector for the Cirrus board, or others, so that if you wanted to you could plug one onto my board... which I have nicknamed 'Kraken' because it will be a tentical monster of great power and destruction. The connector will go to the MCU and be treated just like any other source - would this be bad? I think it'd be OS and RasPi agnostic then - what if you wanted to use a distribution that didn't support the Cirrus card? Or if you don't want RasPi in the system at all?That solves the analog and SPDIF cases for DVD, Blueray & Legacy gear. For a PC, USB Audio is preferred. For iPods, iPads, and phones in general how about Bluetooth? It's cheap now with $20 modules like the RN-52 or BC127.

author: rickey1990
author_rank: Regular Contributor
timestamp: May 15, 2015, 11:12:54 pm
content: Poor old Analogue :0 There is no sound like a valvehttp://www.aliexpress.com/item/Little-Bear-P5-BK-6J1-HiFi-stereo-tube-valve-Preamp-Preamplifier-amplifier-ALX/32278470585.html

author: technix
author_rank: Super Contributor
timestamp: May 16, 2015, 09:37:49 am
content: Quote from: rickey1990 on May 15, 2015, 11:12:54 pmThis is just undiluted audiophoolery l.

author: brentsinger
author_rank: Newbie
timestamp: May 16, 2015, 10:50:49 am
content: I see nipples and boobs. My amplifier is going to have balls. 600W of them.

author: MarkZ
author_rank: Newbie
timestamp: June 15, 2015, 01:37:38 am
content: Hi,I registered for the forum just so I could comment on this thread. I'm really interested in a board like this, enough that i'd consider helping with the kickstarter... but... I have a different view of the board.I'm a speaker guy and the board excels as the insides to a speaker, as you know. I see it as a one-stop active speaker. This means a 24/96 1 or 2 channel A/D for analog input, a single USB for data and control, maybe an spdif, then one additional plug-in for w/e - wisa or aptx or... And I think it has to sell for less than $400. What I honestly don't care about is the pi or the Ethernet - I don't really want the complexity of a pi in a board that goes in a semi-sealed box.Just my 2 cents.Mark