Mayby you can try lowering the input impedance of the NC400, this could help. Try for example a 10K resistor on the hot and cold pin to ground. This would result in a input impedance of ~9Kohm. It could very well be possible that this at least attenuates the transient quite a bit. The load would still be easy enough to drive..
Julf, regarding a thermal problem. The nc400 do not get more than lukewarm at the base, large chassis lots of cooling capacity. Low power used, 98-99db effective Altec 604-8g speakers.
I regrettably dont have an IR thermometer. Also a thermal problem should affect both channels (same box, mounted in the same way) ?
Kjartan
I would put the 10K resistor between the hot and the cold pin. The ground should remain totally isolated from the signal.
Kjartan,
I agree it should affect them in the same way, but maybe one is slightly more sensitive. Anyway, no, with the situation you describe, overtemperature should not be an issue.
Just as a random thing, how about swapping the speakers around, to see if it still is the same amp switching off? Then the inputs, the same way - just to isolate any external factors.
I agree it should affect them in the same way, but maybe one is slightly more sensitive. Anyway, no, with the situation you describe, overtemperature should not be an issue.
Just as a random thing, how about swapping the speakers around, to see if it still is the same amp switching off? Then the inputs, the same way - just to isolate any external factors.
Sure, but why? A 10K resistor would result in a 9K input impedance - ought to be enough.
The nc400 specs give differential mode input impedance as 104 K, and common mode impedance (hot and/or cold to ground) as 1.5 M. You don't want to bring down that from 1.5 M to below 10K...
You still need those caps, they will block any DC. The resistor on the input lowers the input impedance, hopefully this will dampen the transients. If you use 47K it will work but 10K would be more effective. The impedance with a 47K resistor would be ~32K with a 10K resistor ~9.1K.
Because the input impedance is much lower with this mod your cap should be at least 1.5uF (for a cutoff of ~12Hz).
Because the input impedance is much lower with this mod your cap should be at least 1.5uF (for a cutoff of ~12Hz).
I agree. You want the caps to keep the DC away from the speakers, and the resistor will hopefully reduce the transients. With a lower input impedance, I also agree that a pair of 1.5 uF caps is called for. There should not be any impact on sound quality as long as the output stage of the DAC is reasonably low impedance - so don't use a passive volume control / preamp (or a tube preamp).
Ok, since this is all very foreign to me is there any chance either (or both) of you could look at this webpage and tell me what I need (IF you have time, and don't mind helping out/advising). It would just make it so much easier if somebody more knowledgeable than I could tell me what I need rather then me guessing at parts.
https://www.partsconnexion.com/index.html
Julf, the output impedance of my dac is very low, I remember a discussion about impedance came up a few weeks ago and I looked mine up.
For volume control i'm using the volume on my dac. It can adjust volume on the analog or digital or you can bypass it if you have a pre (which I do not).
Thanks guys
https://www.partsconnexion.com/index.html
Julf, the output impedance of my dac is very low, I remember a discussion about impedance came up a few weeks ago and I looked mine up.
For volume control i'm using the volume on my dac. It can adjust volume on the analog or digital or you can bypass it if you have a pre (which I do not).
Thanks guys
Agree, note especially stay away from relay switching attenuators if you have an offset problem. The pops from every time you change volume would really be annoying. The other problem with minimalist "preamps" is that using a pot with DC on it causes noise and premature failure of the pot. It etches the element.
To me the best solution would be to have a dc servo on the output of the DAC, eliminate the dc without the audio going thru a cap. Probably not realistic in your situation.
You could measure the offset of each of the audio signals from the DAC, if one is low then you could use it as a single ended send and be done with your offset problem. You wouldn't have the advantage of balanced operation, but it would function well and unobtrusively. Just keep track of the absolute phase and hook up the speakers accordingly. Ah, the tradeoffs of engineering!
Me, I think Michal has let too much dc get designed into the 192DAC.
(to be complete, I have Mytek A/Ds and I like them quite fine)
Alan
Sure! I would go for 2 x ARCOL-75052 for the resistors, and 4 x SOLEN-55863 for the caps - sorry, but the Parts Connection web site doesn't seem to do direct links to individual components.
Great - so no audible impact!
caps gets into an area of much religion and belief.
most of the caps on that site are geared to tube gear, note the 400V rating. not needed here, nor the price.
for most cost effectiveness look at the MKP-1837 caps
Wima caps of similar style and ilk would also be a good choice. Many people prefer film and foil over metalized. Me, sometimes I think I can tell a difference, other times not. Try Mouser for those, 100V range.
Then we're talking ~$2 each
Alan
most of the caps on that site are geared to tube gear, note the 400V rating. not needed here, nor the price.
for most cost effectiveness look at the MKP-1837 caps
Wima caps of similar style and ilk would also be a good choice. Many people prefer film and foil over metalized. Me, sometimes I think I can tell a difference, other times not. Try Mouser for those, 100V range.
Then we're talking ~$2 each
Alan
Agree. Was about to write "do you really have to get the stuff from Parts Connection? What's wrong with Mouser", but erased it mid-sentence, not wanting to get religious.
100% agreement here.
am I the only one thinking that there should be an unofficial (as in not written by Hypex) NCORE FAQ?
concerning Erlend's problem... some have said that he may be having ripple at PS out. I'm assuming he's measuring with no load (since the amp isn't working). in which case his DMM should be reading peak rectified voltage. he's getting 60 something which is pretty far from the 75V in the NC data sheet.
also supply pumping should not be occurring with not functioning amps. worst case he should be getting intermittent output. but this is only guessing.
concerning Erlend's problem... some have said that he may be having ripple at PS out. I'm assuming he's measuring with no load (since the amp isn't working). in which case his DMM should be reading peak rectified voltage. he's getting 60 something which is pretty far from the 75V in the NC data sheet.
also supply pumping should not be occurring with not functioning amps. worst case he should be getting intermittent output. but this is only guessing.
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