Does this make sense?

No it doesn't make sense

You need to ID the inferior SQ & crackles as that is far from normal or acceptable

What happens if you get an NDS & its still there ???

It doesn't make sense that the Mac is better than the NDX

Far far too many users are satisfied with HDX & your reported problem(s) do not match te experience of these people 

You don't say what your music file source is & exactly how its connected to the HDX,  Ditto the Mac

When I switch to another input as FireWire or other, the crackles are gone. I'm sure it's the HDX

The music is on a Audiodata Musicsever-NAS, HDX is SSD-Version.

What kind of ethernet network do you have between NAS and HDX? This could be an issue....

Did your dealer confirm that your BNC interconnect was ok (e.g., properly terminated, 75 ohm)?

Have you tried using Toslink between your HDX and Weiss dac?

I have an Airport Time Capsule in the office upstairs and Airport Extreme as an extension in the living room. As I wanted to have the Extreme as far away from my rack I have a small switch under the Fraim from which the NAS and HDX are connected via Meicord cables

No I haven't used Toslink because Naim and others say it's SQ is inferior.

Why not get the first issue sorted out - i thought Naim were looking at the dropouts on the S/PDIF output on the HDX and would issue a fix. Speak to them first. 

NDS into 202. I'm not sure what that is going to give you over the HDX / 202. The 202 is a great DAC (i used to have one) but using the NDS as an S/PDIF source is overkill. Are you running the 202 straight into the 250.2 and using the volume control in the 202 so it's acting as a DAC / Preamp ?

James

I use the DC-1 as interconnect between the HDX and the DAC, so I think this should be fine

Sure, I'm waiting eagerly to see a solution from NAIM. But I still have the impression the SQ of the HDX is inferior to my MacBook, especially lacking warmth and bass. 

Yes, I'm using the DAC 202 as preamp too, directly connected to the NAP 250.

The toslink will help you trouble shoot if the BNC connection or cable is the issue.

If you get an NDS, no way should you use the Weiss, though of course you'd need a pre-amp. You could cast another vote along with me for Naim to produce a DAC-less streamer.  

But, if you like the Weiss sound - keep it. There are a lot of streamer/hard disk player options: I have a Sonore Rendu which is  a DAC-less streamer. It has ethernet in and SPDIF out. You need a NAS with a UPNP server. Another option is the Aurender products or something like a Computer Audiophile CAPS server, both of which would be USB out to your DAC, and probably could be configured with fire wire. You should be able to use your same hard drive you have connected to the HDX. Though, I'm not sure how the HDX does the file formatting.

Hmm - i didn't find the Weiss driving a Naim power amp a very satisfactory arrangement. I'd get the 250 fronted by a decent Naim preamp - 282, 252 (yawn) + Supercap. 

Ok, will buy a Toslink cable see what's happening.

Just a few information why I chose the Weiss Dac. I started with a Uniti, added a HDX,  then the NAP 250 and later on the Naim DAC. I felt the Uniti was the bottle neck of the system. Next step would have been a preamp. I didn't want to increase the box count by two (preamp plus power supply). I was looking for a sleek system. So I decided to sell the Uniti and the DAC and buy the Weiss DAC as it is a DAC with Volume control so I could go directly in the NAP 250.

I'm really not happy with the SQ of the HDX although I have a XPS2 DR. Just to explain the difference

take the latest album by Daft Punk (highres from HDTracks). When I play the first song over the HDX the music sounds thin, lacking bass and warmth. Play the same track from my MacBook Air and there is more of everything and it get's me food tapping.

Well, this may depend on the cable used between the Weiss DAC and the NAP 250. I find it sounds very good. A preamp and power supply is not really an option, because of place restrictions and WAF.

So the idea was to improve the source, that's why I was thinking about the NDS, but as mentioned, dig out from the NDS to Weiss DAC would be overkill. I definitely wish Naim made a streamer in the class of an NDS without integrated DAC. I probably have to consider, as suggested, streamers by Aurender or others.

I'm pretty sure it wasn't cabling. A 282 in front of my 300 (at the time) sounded better than the DAC202 > 300. Most Naim power amps aren't at their best without a Naim preamp fronting them. 

Just looking again at what you have i'd - 

Keep the HDX - use it as the ripper and server. Stick it somewhere on the network. 

Sell the XPS2 and sell the DAC202. 

Get a Superuniti - either use it standalone or with the 250. 

I'd go to a dealer and listen to the various options to make sure your requirements of minimum box count and maximum SQ are met. 

A friend uses a Weiss and from what I can recall, the Firewire is better than the USB and SPDIF, but he reckons it's best used with a Stello U3 USB/SPDIF convertor. I suspect the USB implementation on the Weiss isn't quite up to scratch. I notice Apple no longer supply their 'puters with Firewire connectors. Wonder if someone's going to come up with a DAC with a Thunderbolt interface?

The Weiss is sensitive to noise coming in via the Firewire input - something easily demonstrated by using using a 6 way to 4 way converter to break the 5V connection at the computer end. I can see how the USB > S/PDIF converter can work well here (particularly if care is taken over local generation of a clean 5v line etc). When I last had a DAC202 in the house (our mutual friend brought his over), I preferred the Mac > Firewire > 202 to my NDX driving the 202 via S/PDIF. 

IIRC James, our mutual friend uses an iFi USB supply.

As long as your Weis has the 'drive' current required to drive your cable and the high (I would hope) impedance input of your NAIM poweramp, and you have all the control you require then stay as you are.  As you say it sounds fine with your Apple but not with the NAIM box, so it is nothing to do with not using a preamp box.

Have you yet tried the optical connection?  People say that it is inferior to coax but you will also find people who say the opposite.  So the best course of action is to ignore them both.  If you can lay your hands on one then give it a bash, it's a useful connection to have around because lots of kit just has an optical output - eg most TVs.

btw it might not be a cabling issue but there might be a fault in the coax S/PDIF output, so worth a check.

I must admit that I am absolutely astonished that the Apple sounds better than the HDX, not very good for NAIM's marketing.  Have you been able to demonstrate to your dealer this difference in SQ between the two digital front-ends?

If it's the set-up I'm thinking of, the other variable suggested by a review you can find searching 'positive feedback review of Weiss 202' is the change from Firewire to Spdif also involves a change of clock sync.

Something in the chain of iFi clean 5v USB line - Stello U3 - Weiss spdif coax takes it's performance to a higher level than the same Mini/aiff files delivered by Async Firewire.  Unlikely to be the potential noise element on Firewire as a 4 pin /6 pin arrangement was already taking that out.

Joe

Given the various problems with the HDX that the OP reported, it's far from clear that an HDX, working properly, 'sounds worse' than the Mac Mini.  The OP needs to sort out what's going on in his system, first and foremost.

I bought some bad fuel one time and my BMW ran like crap. The metaphor may be apt; we won't know til the OP has sorted things out.

At first, thanks for all the replies.

I bought a Toslink cable this week-end, and guess what, the dropouts have disappeared, also when turning lights on or off in the house there are no more dropouts. For the SQ, I just listened to internet radio, so I can't comment on SQ so far. I will take the time and listen carefully and keep you informed about the results

Gaudenz

???  Tell us more about this piece.

Sounds like a serious case of chronic leckyitus. 

Needs a visit by a multi-mega doctor

This sounds like earthing problems in your house wiring to me.