The gain of the NCD is pretty high, so if anything before the amp does not have good noise specs, then you will hear noise. If you disconnect the pre from the NCD and hear no noise, then this is probably the casue.
The NCD seems to have a floating ground, about 10Ohm resistance between the NCD ground and the chassis if I remember correctly. I don't think this matters.
The NCD seems to have a floating ground, about 10Ohm resistance between the NCD ground and the chassis if I remember correctly. I don't think this matters.
Bitnissen: Based on your statement that the noise more or less disappeared when pushing the mute button on the preamp, i would say the problem is in too high gain in the power amp.
You can solve this very easily by connecting a 10k resistor in series with both + and - input of the amplifier.
Mount these resistors directly on the NCD module's input terminals, then you will be fine. Use good quality resistors like for example Dale CMF55 series. You can get them from www.digikey.co.uk. Other types will do as well, but at least use non magnetic types for best sound quality.
You can solve this very easily by connecting a 10k resistor in series with both + and - input of the amplifier.
Mount these resistors directly on the NCD module's input terminals, then you will be fine. Use good quality resistors like for example Dale CMF55 series. You can get them from www.digikey.co.uk. Other types will do as well, but at least use non magnetic types for best sound quality.
Yes this is intentional, so to allow you to connect several modules together on the input side as well as the power supply side without creating ground loops, that will otherwise cause hum or other noise.
For wiring instruction, please just download the cookbook, which is the instruction for the module.
You find it here:
http://www.newclassd.com/index.php?page=15
For wiring instruction, please just download the cookbook, which is the instruction for the module.
You find it here:
http://www.newclassd.com/index.php?page=15
No, but when you use a VR / potentiometer the impedance of the signal increases very much, causing for influences from the cable dielectric to increase vastly.
That is why you can benefit from using a good buffer. A very high impedance tends to sound better than a low impedance one, that is why i recommend the OPA627, as it has the DIFET input stage.
Lazy
I've got rid of the potentiometer (to much loss of detail) but was to lazy to build a buffer and inputselector.
The solution presented itself : 70% discount on a brand new audiolab Volumecontrol/input selector...(8000Q)!!
Yes, I know : easy way out, but for this kind of money there is no alternative...
Cheers, Eric.
I've got rid of the potentiometer (to much loss of detail) but was to lazy to build a buffer and inputselector.
The solution presented itself : 70% discount on a brand new audiolab Volumecontrol/input selector...(8000Q)!!
Yes, I know : easy way out, but for this kind of money there is no alternative...
Cheers, Eric.
Attachments
Anyone have EMC trouble with their NCD?
Hi,
Was just wondering whether I'm the only one to experience EMC trouble with my NCD1?
It disturbs the DAB and FM radio quite a bit (doesn't seem to affect Wlan, BT, GSM or DECT phone though).
For the time being I have tolerable DAB reception by moving the (indoor T-type) antenna as far away from the NCD & speakers as possible with a piece of Coax wire, and clamping some ferrite cores onto the cable, one right at the antenna connector on the DAB reciever. I have noticed that I have to keep the Coax wire away from the speaker cables, otherwise reception quality goes bad.... but this isn't really a nice long-term solution.
Besides, even with ferrites etc., reception is bad for a while just after turning on the NCD (as though it has to "settle in"), then reception seems to improve. Also, there is trouble at sunrise and sundown. In all cases, turning off the NCD immediately restores singnal quality (as gauged by the tuner's display) and audio reception (headphones).
Unfortunately, I can't get good FM reception with the NCD on at all.
I guess I should mount the EMC kit that Lars suggests in his cookbook, but... I've written to him a couple of times asking whether he would send me one, and no reply so far :-(
But is the EMC kit really necessary...? or is there something else I should look into first? I have a couple of holes in the back of the enclosure - for XLR jacks which are currently not mounted - I was wondering whether I should close them?
All devices in the hifi chain are connected to ground w. 3-prong connectors, and connecting a wire straight from the NCD case to the DAB reciever case doesn't make a difference. Internal NCD wiring done by the book except for a modification of rectifiers to support 33-0-33V transformer (yes I know this is inferior to using a transformer w separate windings).
Anyone have similar problems, or suggestions?
I will hurry up to say that - other than the radio reception problem - I have had no issues with the NCD whatsoever, and am EXTREMELY happy with the sound quality - never heard anything better.
thanks, cdl
Hi,
Was just wondering whether I'm the only one to experience EMC trouble with my NCD1?
It disturbs the DAB and FM radio quite a bit (doesn't seem to affect Wlan, BT, GSM or DECT phone though).
For the time being I have tolerable DAB reception by moving the (indoor T-type) antenna as far away from the NCD & speakers as possible with a piece of Coax wire, and clamping some ferrite cores onto the cable, one right at the antenna connector on the DAB reciever. I have noticed that I have to keep the Coax wire away from the speaker cables, otherwise reception quality goes bad.... but this isn't really a nice long-term solution.
Besides, even with ferrites etc., reception is bad for a while just after turning on the NCD (as though it has to "settle in"), then reception seems to improve. Also, there is trouble at sunrise and sundown. In all cases, turning off the NCD immediately restores singnal quality (as gauged by the tuner's display) and audio reception (headphones).
Unfortunately, I can't get good FM reception with the NCD on at all.
I guess I should mount the EMC kit that Lars suggests in his cookbook, but... I've written to him a couple of times asking whether he would send me one, and no reply so far :-(
But is the EMC kit really necessary...? or is there something else I should look into first? I have a couple of holes in the back of the enclosure - for XLR jacks which are currently not mounted - I was wondering whether I should close them?
All devices in the hifi chain are connected to ground w. 3-prong connectors, and connecting a wire straight from the NCD case to the DAB reciever case doesn't make a difference. Internal NCD wiring done by the book except for a modification of rectifiers to support 33-0-33V transformer (yes I know this is inferior to using a transformer w separate windings).
Anyone have similar problems, or suggestions?
I will hurry up to say that - other than the radio reception problem - I have had no issues with the NCD whatsoever, and am EXTREMELY happy with the sound quality - never heard anything better.
thanks, cdl
Re: Anyone have EMC trouble with their NCD?
Wasn't that EMC kit a few caps and a piece of tape?
I wouldn't worry too much about not getting that or even the lack of email response, everything is status quo so far.
Your choice is to live with it or swap it for something more respectable. Say, perhaps a 555 with a relay chopper and a 627 input stage for the detail.
Hopefully your neighbours aren't relying on a babymonitor.
Wasn't that EMC kit a few caps and a piece of tape?
I wouldn't worry too much about not getting that or even the lack of email response, everything is status quo so far.Your choice is to live with it or swap it for something more respectable. Say, perhaps a 555 with a relay chopper and a 627 input stage for the detail.
Hopefully your neighbours aren't relying on a babymonitor.
Re: Re: Anyone have EMC trouble with their NCD?
True, the EMC kit is a few caps, some ferrites and a strip of copper. I suppose I could get those things together from somewhere else, but now that NCD offers to supply it, why would I?
Somehow this doesn't strike me as particularly constructive? Maybe there's something in your post I don't understand - in that case please forgive me and feel free to explain yourself further. If you have any ideas as to what I might do to control the EMC - other mounting the aforementioned caps and ferrites - well, I'm all ears.
Best regards - cdl
classdphile said:Wasn't that EMC kit a few caps and a piece of tape?
True, the EMC kit is a few caps, some ferrites and a strip of copper. I suppose I could get those things together from somewhere else, but now that NCD offers to supply it, why would I?
classdphile said:
Somehow this doesn't strike me as particularly constructive? Maybe there's something in your post I don't understand - in that case please forgive me and feel free to explain yourself further. If you have any ideas as to what I might do to control the EMC - other mounting the aforementioned caps and ferrites - well, I'm all ears.
Best regards - cdl
Thanks for your reply, Eric 
Well, you are right - if i'm annoyed long enough, i'll probably get the parts myself eventually - just easier to have Lars send me the right stuff ;-)
If you actually mounted the EMC kit (or similar), did it solve the problem?
Would be nice to know before I take the beast apart (it's not in the most practical enclosure).
Best regards, cdl
Well, you are right - if i'm annoyed long enough, i'll probably get the parts myself eventually - just easier to have Lars send me the right stuff ;-)If you actually mounted the EMC kit (or similar), did it solve the problem?
Would be nice to know before I take the beast apart (it's not in the most practical enclosure).
Best regards, cdl
You really should keep pestering Lars seeing as he's offered them to solve an obvious and known shortcomming, you are owed them.
Surely he doesn't simply offer such things knowing they don't work and then ignore the emails requesting them?
Besides should you go and get the parts yourself, once they don't work there could be the excuse that you didn't get the right parts for the job. Remember to disinfect before applying (helps the glue adhere).
You should expect at least as much from it as you might from trying to tame a forest fire with sunglasses.
Surely he doesn't simply offer such things knowing they don't work and then ignore the emails requesting them?
Besides should you go and get the parts yourself, once they don't work there could be the excuse that you didn't get the right parts for the job. Remember to disinfect before applying (helps the glue adhere).
You should expect at least as much from it as you might from trying to tame a forest fire with sunglasses.
classdphile said:
In theory you might be right, but for me I don’t like to “pester” anybody, especially not for something worth of 5,= euro.
To me, it is just an perfect excuse for another ride down-town to visit my “parts dealer” and sniff around. Is it not what we are here for anyhow : A little DIY ?
Ceers, Eric.
That's some enthusiasm, Berns
my purpose of posting here is triple:
1) I'd like to hear whether others have EMC issues with their NCD's- if not likely that there's something wrong with my implementation (since Eric has it too, so far no indication of error in my setup).
2) I'd like to hear some more opinions on whether the EMC kit might solve the problem, before I go through the trouble of mounting it... (and getting an extra set of caps & ferrites since I have dual output terminals wired separately all the way to the amp module output). (So far all I have here is that you don't seem to think it will do much good).
3) As you pointed out, Lars must be offering the EMC kit for a reason - and with the intent of actually sending it to those who need it. My emails may have been lost in a spam filter or in piles of work, so I'm hoping to catch his attention in here.
Thanks for the tip about the disinfectant.
/cdl
my purpose of posting here is triple:
1) I'd like to hear whether others have EMC issues with their NCD's- if not likely that there's something wrong with my implementation (since Eric has it too, so far no indication of error in my setup).
2) I'd like to hear some more opinions on whether the EMC kit might solve the problem, before I go through the trouble of mounting it... (and getting an extra set of caps & ferrites since I have dual output terminals wired separately all the way to the amp module output). (So far all I have here is that you don't seem to think it will do much good).
3) As you pointed out, Lars must be offering the EMC kit for a reason - and with the intent of actually sending it to those who need it. My emails may have been lost in a spam filter or in piles of work, so I'm hoping to catch his attention in here.
Thanks for the tip about the disinfectant.
/cdl
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