WAF Najda ADC / DSP XO / DAC's all in one

[Magna Audio]

Thought I'd share this with AoS'ers. It could just as well sit in the DIY forum but it is Line level digital too...

Having tried Behringer DCX 2496 and giving up as my knowledge and skill in these things is not as Mr Coco's, a while back I committed to try this new WAF Najda DSP X/O project.
There's a long thread on DIY audio for those interested in all the details - http://www.diyaudio.com/forums/digit...-part-2-a.html

It's supposed to be a challenger and exceed the miniDSP offerings and should blow a standard DCX2496 out of the water...
A 3 way DEQX is several grand! Two of them chained for my 5 way would be ~£6K! Out of the question and questionable if they are better.

At 300 Euro's + parts to complete Najda is keenly priced. A DCX2496 is cheaper but only 3 way and after mods costs much much more.

The board arrived last week and I acquired the bits I needed - +/-12V and 5V PSU, 16x2 display, a few 5V LEDs and 8 push to make buttons.

Not knowing what to expect sound wise, I have put minimum effort into the build case wise - functional yes, pretty no!

Here it is all wired up on a test mule - no point in going further had it sounded cack!



Underneath the black box is a very high freq, low ripple and good regulation open frame switching mode PSU. This is an area that may see future improvement... Ready made linear +/-12V, 5V PSU's are virtually non existent to buy it seems. Other suggestions welcome...
I might make one, as a chap on the DIY forum is planning on doing just that...

Checking the supply and all my wiring a few times... This is not a forgiving valve amp build - nano second of wrong juice here and things are fried, game over.

She powered up just fine and after a shake down of functionality all was well. Connected up the PC for fuller config and setting up the channels.

Here's a pic of the board detail.



The rows of unused outs are for expansion boards - So when they are available, 6 channel is possible. At the moment it's 4 channel.

So, with it acting as a DAC - Coax in, the gain structure is perfect on both input and output. The outputs can be configured from 1V to 6V. I have them on below 2V.

It is configurable to change the gain on input and output but I have no need so far.
There's IR remote capability all it needed was the IR sensor for £1 and a cheap One for all remote - the codes for JVC and NEC devices are all pre tested - it worked no problem at all.

Just playing it straight through with the passives still in place I could hear this was streets ahead SQ wise of Behringers cheap and cheerful DCX2496. The ADC also works really well.

As it is 4 way (only), I have piggy backed the tweeter amp for the Raals on the open XO upper mid channel and used a 1uF cap for 1st order passive - as I did before.

How does it sound playing open doing the DAC work? - Well pretty good actually. Very composed and not fudging the sound as the Behringer did. I never tried coax SPDIF in to the Behinger as vol control was not there so in fairness it may have been better like that.
Modding the output stages as Coco has done def improved it but what a project...
This one has a very nice vol control from -96dB to 0dB.

I must say the guys on DIYaudio are always very helpful and chapark (Nick the designer) is most responsive and helpful.

Onto using the X/O slopes.
Simplicity itself: configured here for a tapped horn. Just click and set the others how you want them.


Front control panel


9 setups can be stored on board and are instantly switchable via the panel or remote. There's L-R balance, mute etc too.

DSP correction is possible. I've eradicated the need for Antimode on the tapped horns and applied a little correction on the mid bass too.
No correction needed or ever sounds good on compression driver horns to my ears so best left well alone.

Moving the project on I have measured and played a lot.
Learning that the mighty Vitavox S2 compression drivers respond better to a 1st order BW XO in the form of a 3uF cap! Anything else chokes them!
No problem as I use DSP for Tapped (sub), Midbass and then run the mids and upper mids with no XO in DSP and use the passives.
That way I can time align all 4 channels and manually time align the tweeter by physical positioning. Best sound by far like this.

The flexibility of DSP XO's is brilliant in a 4/5 way project. There is none of the phase shift issues as with passives and none of the rising impedance (needing SQ choking Zobels) either.

I decided to re-house as Najda is a keeper.

Box from Hong Kong (they pre drilled the holes for me too)


Test siting the board and PSU



A template aided the cutouts and drillings for all the RCA sockets, USB, optical etc



All finished - display countersunk in to be flush - that took some work!



Next job is to sort out some lettering for the LED and button functions. As a stop gap I've written them on in perm marker - looks ok in a rustic sort of way

The correction in my room is far better than Antimode offered and can be on all channels if needed - ok you have to measure and DIY it but the result is top drawer and so much more flexible - you are in control.

Here is the tapped horn and mid bass - no correction



Here again with cutting only correction - I learned this form a DIYaudio'er - only ever cut, adding taints the sound.



With careful XO freq choice to work the room I get a 20-20KHz plot like this. Remember - no correction on the upper 3 channels.




So what does it sound like now?

Well absolutely stunning TBH. All the transparency of the passive set up but with much improved bass. The benefit of time aligning the tapped horns as well as the rest is noticeable. This is just not possible in the passive world (would need 9m (I think it was) position shift!).

It also works excellently with ADC too. The on board DACs are as good as my original DAC. I no longer need the Puresound L10 pre or the DAC.

It's dead quiet in operation and reliable as the proverbial (touch wood).

Coco got one too having read my exploits. His heavily modded Behringer pare are now dropped from the lineup - say no more.

If anyone wants more info or would like me to build them one - drop me a PM.

[Ali Tait]

Well done, looks very interesting!

I use a Behringer currently, might give one of these a whirl. Does the chap have a web site?

[Magna Audio]

Well done, looks very interesting!

I use a Behringer currently, might give one of these a whirl. Does the chap have a web site?

Yep
http://www.waf-audio.com/

BTW. I run mine at 96KHz. 48 was noticeably low res and 192 made the highs a big odd.

[Ali Tait]

Thanks, I'll have a look.

[Magna Audio]

Thanks, I'll have a look.

Yes, well worth it. The SQ, features and flexibility are really up there IMO / IME. I am very critical about what comes out of my 5 way system and the improvement over passives on the bass channels is impressive.
The Vitavox S2's are super critical about how / where you cross them and I prefer the 3uF cap sound. On other drivers Najda would be fine I have found.

[realysm42]

Looks like an interesting piece of kit.

The question I've got is: if I've got an asynchronous USB DAC, how would I incorporate this or any other device without USB output into the system and keep it asynchronous?

[Magna Audio]

Looks like an interesting piece of kit.

The question I've got is: if I've got an asynchronous USB DAC, how would I incorporate this or any other device without USB output into the system and keep it asynchronous?

Sorry for the slow reply, not looked on digital for a while.

I stream from computer source USB into a converter to optical and then into Najda. Not asynchronous as no feedback loop, but it sounds fine when compared to CD SPIDF input and analogue. I am super critical of how this system sounds compared to what I had in all analogue / my own DAC of choice before and cannot really fault it sound wise.
My speakers are perhaps one of the most revealing setups available too.

If there are good motivations for going asynchronous then I am sure the designer (Nick) would be happy to discuss and possibly incorporate if/when next updated.

I asked Nick on DIYAudio and he replied thus:
"Hmmm... Honestly I don't understand the question.
If it's just a DAC then you don't need it with Najda - Najda has its own set of DACs.
If the device outputs I2S, then you can connect it to Expansion Port 1 as explained in the manual and stream USB audio straight into the system. This is the preferred option.
If the device has SPDIF out, then you can connect it to one of Najda's SPDIF ins.

My understanding about this asynchronous stuff is that the data collected from the USB line is stored in a buffer and re-clocked onboard. In order to transfer the audio data to another device, you need to transmit a clock as well, so the transmission gets synchronous again. In clear, the asynchronous stuff applies only to the buffering part of the USB device; as soon as you want to use the data, it becomes synchronous again, whether you send it to the onboard DAC or transmit it to another device.