Front-end stack for active 4ways: wifi/bt L, R, vol -> DRC+XO -> DACs

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I'm building a pair of active mains with embedded electronics. I'm trying to get away with only running one cable to them: AC. Hence, I'm looking for an electronics chain looking smth like this:

Volume+Audio Stream receiver -> DRC+XO -> DACs -> power amps (I got this covered)


I'd _much_ prefer if the audio/volume receiver was wireless, and either supporting AirPlay directly or receiving data from an AirPlay bridge. The bridge could run on a Mac/PC/Linux system.

I love to tinker, but don't have time or desire to re-invent wheels so would prefer a proven solution (or set of solutions) even if it's a bit more costly. Obviously it'd be awesome with a board supporting this entire front-end, but I've only been able to find bits an pieces, and they don't necessarily seem to mesh very well. Any help would be greatly appreciated!

I would keep everything separated !
Total weight will be distributed equally
Each function to its form.
The speakers would be...speakers and be free to move wherever
The amplifier would be the...angry beast it is

Since the integration has to happen in the environment where we listen to the music
It works like that....
Or maybe you liked particularly some kind of active monitor and you want to make one ?
Not that I am 100% sure that this will work, but have you seen these networking adapters that route traffic over the power line (locally, e.g. in your home) as an alternative to wireless? Since you will have AC power cord running to the speakers, you could send the audio via ethernet and have a receiving device inside each speaker (Raspberry Pi?). You would need a way to send the audio over TCPIP, but I assume there is a solution for that kind of streaming already available. This is kind of getting outside my realm of understanding...

From the outside, you would see one cable.

Lots of options at NewEgg:
Powerline Networking, Powerline Adapters -

I would love to know if you figure out how to make this work, because I am building something very similar. I am not trying to have one cable, but will have separate AC and then use SPDIF (probably toslink) for the audio stream. A DSP crossover unit in the speaker will accept the digital stream, and output analog to the amp connected to each driver. If there is a solution in which I can just use the AC main for all of this, then I am all ears.

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@picowallspeaker my wife thinks it's enough with one angry beast in the house, i.e. me. :)
Seriously though, I have decided to build an integrated high-end system. Think Klein Hummel o500, Genelec 8260, and similar.

For the DSP there seems to be some good solutions like MiniSHARC or MiniDSP. However, I need to deliver the audio signal to each speaker, control the volume, and do DA conversion. This needs to be done with minimal phase shift from L/R channel. If it is not feasible to deliver audio wirelessly without building something custom I will settle for delivering the signal over coax, but I still need to control the volume of both speakers.

@charlielaub the idea about delivering the audio over Powerline is interesting; my main concern here is keeping the playback from L+R in sync; there might be time shift if there are two independent Raspberry PIs processing the signals separately.
I you run run two separate DA conversions, the synchronization will be hard to maintain as the timing element is always the soundcard. Two soundcards mean two independent clocks which will eventually drift apart.

Technically it can be solved by adaptive reclocking, practically e.g. jack with zita-ajbridge . However, it is not a simple solution and requires quite some CPU power.

I would suggest to run a single DSP/DA chain in one location and distribute the final analog signals in balanced form. E.g. shielded cat5 can transfer 4 balanced channels. If a bit of crosstalk happens it should not matter as it is the same channel split by frequency. Practical application e.g. XLR over Cat5 - Balanced XLR Mic-Level & Line-Level Audio over Cat5 & Cat5e Cabling | Life is a
Off The Wall...

Hi guys,

I am also trying to get rid of as many boxes and cables as poss, my speakers are " hang on the wall" and I am building in the DAC's and power amps into a slim power pack which fits between the speakers and wall, the whole lot is less than 8 inches deep.
The attached Zetex is a great bet for a one box solution, power / DSP / DAC's / Room Eq, / crossovers etc.
I know of one UK manufacturer who has just ditched a suite of TI
DSP and amp chips in favour of Zetex, the technology is very clever and the eval board I heard was very good.
You can use conventional power amps / DAC's / DSP and use a 5.8 GHz band WiFi router as an option. Modern WiFi has the bandwidth to send / recieve a Blu Ray video plus Hi Def 5.1 channel soundtrack so it has no probs with a 3 way active stereo set up at 24 bit 96KHz.


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Hey Overkill,

Good handle:)

This looks quite interesting; their website doesn't respond at the moment though. Do you know:
- Do they sell boards or just chips?
- Since they quote 250W I assume this is for a board. Is it 4x250W?
- Does it support FIR filters? How many taps?
- How much does it cost?
- Do they have their software for programming it?

Are you delivering your digital signal over Airplay or some other way?

Zetex stuff

Hi Gvr,

Yes, Overkill by name & by nature, I do tend do things to excess or not at all...!

Right now I think the easiest option is to build a mini ATX music server round a low power ( 5 to 17 watt max) i3 core chipset and Wi-Fi enabled mother board, (Asus do a nice one) and " stream " the music to an off the shelf Hi Def. WiFi receiver which feeds in to the USB input of the DAC's and then straight into the power amp.
Running windows 7 or 8 and JRiver 18 you can control the whole thing from a smart phone or tablet. You can add in great studio plugins / VST to JRiver if you want to, anything from basic Eq to sophisticated crossover and RTA's.
BlueCat Audio and Fab Filter have a great range.

Once that is built using really good DAC's and power amps that will be my reference and then the goal will be to try to match it or surpass the end result with a simple one box solution from Zetex.

The Zetex stuff used to be large volume OEM only, but now they will do Evaluation boards and I think the MOQ for the chipsets is now low enough for a group buy on DIY forum if someone / or a few guys could team up to put the resource into writing the firmware and sorting out a display and interface.
A huge bonus of the Zetex solution is that the entire source to speaker terminals system can be run from one or two LiPo 4 batteries...Imagine total freedom from mains noise (and power surges) and all the sonic benefits of PS with huge current reserves and no hum / ground loop problems?
Also no mains cables / power conditioners...& while we are at it no cables or interconnects ( WiFi @ 24bit 96K or higher is easy), no wonder all the snake oil cable / power conditioner / vibration tuning etc companies are scared of Zetex!

The market potential for a one box solution that can equal or surpass the Twisted Pear / Hypex / DEQX gear is massive. One UK company is now developing such a solution and many others will ( have to?) follow as it will really be the only game in town...
The future is bright, the future is Zetex!!

PS I have no affiliation with Zetex but I would sure love to kiss goodbye to all the overpriced PCB's / huge power supplies/ and designer audio boutique components at silly prices....
Afaik Zetex DDFA stuff is used in famous NAD MA51 and other NAD PCM/PWM full digital amps. They've got quite a good rep.

Are there any other known products that use Zetex tech
out there?

When can those EV modules be expected ??

When it comes to solutions:

1 MiniDsp NanoDigi with 1* SPDIF in - 4 * SPDIF out.



feeding via SPDIF


HifiMeDiy Fulldigital amp modules in the speaker.

That would still require 24V at least to be supplied to the speaker.
Zetex Ealuation boards

Hi Soundcheck,

I heard a fully functional Zetex amplifier last month and it was very good.
It was configured for multi channel ( I think 5 Ch of 50 watts each Ch) and I only used two Ch, it was very close to my own power amp in overall performance, there were 10 people in the room ( large room with good layout) and most preffered the DDFA!!

My amp is a 22Kg Class A / B ( up to 5 watts class A)using a specially made UK power supply and modified power amp modules from Belles in the USA.
It sounds great but is big, hot and heavy...
The DDFA is the size of a paperback book, runs cool as a cucumber and weighs 2Kilio's!!
The fact that the DDFA also is a full blown DSP / Eq / crossover / DAC etc is just amazing.

I am now persuing a MOQ directly with Zetex in the UK and depending on the investment required, I will try to pull together a DIY forum team and set up a group buy later this year.
I will need some help with the firmware and control interface so please let me know if you will have some time in the summer?

The DDFA is the size of a paperback book, runs cool as a cucumber and weighs 2Kilio's!!
The fact that the DDFA also is a full blown DSP / Eq / crossover / DAC etc is just amazing.

I am now persuing a MOQ directly with Zetex in the UK and depending on the investment required, I will try to pull together a DIY forum team and set up a group buy later this year.
I will need some help with the firmware and control interface so please let me know if you will have some time in the summer?


Hi Derek,

I have been working with the Zetex amps - and have also a much improved driver stage design with galvanic isolation between the driver and output JFETS :) The driver high current pulses (noises) are the major problem in all switching amplifiers...
The 2 kilos are only a "dream" if you want the real SQ out of the design.
I have a prototype with a proper linear power supply (180.000uF) pr. channel that have nearly the SQ of my JFET class A amps. The difference are that I get annoyed with the switching amps as time passes by..
You cannot directly hear anything wrong, but after some weeks it is a relief to switch back to the JFET class A amps... I have made my own custom coils for output filtering etc. etc..
Have Zetex still the requirements regarding NDA etc. as they had a couple of years back ??
Hi Soundcheck,

Thanks for the input. Right now I have a Mac Mini for DSP/XO hooked up to a RME UFX that I'm planning to run XLRs from to the amps in the speakers. If I'm going to run four a bundle of cables, I feel they might as well be analog so I have access to in practice unlimited DSP power.


Are you planning to put together an MOQ for boards or for the chips? Do you know what quantities are required? I'm working on a pair of active 4-ways and this sounds interesting to explore. I am a software engineer; I think I might be hard for me to find the time for yet another side project, but it sounds fun. What does their stack look like today and what software is in your opinion missing?

MOQ boards

Hi Guys,

I think it would have to be a deal on the eval boards as building up a system from the chipset on its own will be a major project.
I think both DigiKey and RS Components supply the chipsets in low MOQ, but you really have to have a lot or resource to do all the design and R&D to go from chips to finished product.

The chipsets are not under NDA but the eval boards are.

Gvr, I think the project will need a lot of software / firmware / interface development, but the end result would be worth it, pretty much game over as far as source / electronics goes, and makes the loudspeaker interface so much easier with the DSP crossovers and Eq.

I kind of agree on game over; hooking all these different products up feels like a very dated and dumb approach for small volume products since you don't care about a few unused outputs, a bit too much power, or whatever excess capacity there is, and on high volume stuff you probably want custom boards.

What software does the eval boards ship with? None?

Hi Marcus,

The amplifier I heard was fully functional with a good basic software and user interface, easily up to dealer / show standard, but would require some slight customisation for end user.
I am not sure if it ships with that level of "plug and play" or whether this is one of their demo units that they give out on loan to OEM's.

I hope to have a more detailed spec of MOQ / spec / support / by the end of the month.

One thing they have made clear is that they wont supply a one man band working out of his garage... So I am out! LOL
They will deal with me if I have ( a) enough cash to buy the MOQ upfront & (b) the recource to develop the product without them having to hand hold all the way... I need help from a team of DIY guys who can work together and make a group buy happen and then make the R&D a realistic project.

Even if it takes 6 months or a year ( as many DIY projects take this long) the prize is worth it.
Ah right, I think all the basic crossover and Eq functions are available on the eval board.

As soon as I can get up there for a visit (maybe next week) I will know more, until then I am just kind of guessing based on a short phone call with a sales guy who told me the technical DDFA guy is on holiday but he will try his best to help!

I wouldn't be interested to do complex and usally compromised DSP on a standalone system.

The DSP work should be done on the PC/server. And the digital amps which reside inside the speakers will get a plain PCM signal via SPDIF/AES/Toslink.


Do those amps have VCC based volume control al la TI (VCC of output stage) .

To me that would be a key ingredient for a useful project. Many of the solutions I've been trying doing too much volume/gain control and driver leveling in the digital domain.

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