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Old 1st March 2013, 07:54 PM   #6491
3lviz is offline 3lviz  Finland
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Have you built an RC lowpass filter in the nCore inputs? I did that today (R=390R, C=15nF), and it seem that in my case it was an upgrade. I have M-DAC as a pre-amp. The change was suggested by M-DAC designer.

Last edited by 3lviz; 1st March 2013 at 07:59 PM.
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Old 1st March 2013, 08:27 PM   #6492
Julf is offline Julf  Europe
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Quote:
Originally Posted by 3lviz View Post
Have you built an RC lowpass filter in the nCore inputs? I did that today (R=390R, C=15nF), and it seem that in my case it was an upgrade. I have M-DAC as a pre-amp. The change was suggested by M-DAC designer.
What was his/her rationale for it?
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Old 1st March 2013, 09:42 PM   #6493
3lviz is offline 3lviz  Finland
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Originally Posted by Julf View Post
What was his/her rationale for it?
M-DAC is very good sounding DAC and preamp. However, apparently it outputs some HF artifacts.The M-DAC designer suggested to use input filter with 30khz cut-of frequency. He also said that there has been some problems with UCD modules in the past locking into HF freqs coming from a DAC, since the HF artifacts were too close to the pwm freq of the amp, which of course caused unwanted effects. He did not have much knowledge of nCore tho.

True or not, I had the parts ready, so I am giving it a try. So far, i am liking the mod. But time will tell...

Last edited by 3lviz; 1st March 2013 at 09:47 PM.
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Old 1st March 2013, 09:50 PM   #6494
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Default That...

sounds like a really strong filter though? With a corner frequency around 27K, of course, shallow slope...
Please let us know what your subjective observations of the differences are. I would also like to hear from anyone who has coupled the input of the nC400s with a good transformer. I have heard people often mention how some class D amplifiers are very sensitive to RF on their inputs. Considering the high input impedance of the module, a really good transformer at its input would have little downside, and if the nC400 is sensitive to HF hash, a transformer could be a good a thing.
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Old 1st March 2013, 10:01 PM   #6495
3lviz is offline 3lviz  Finland
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Yes. The original suggestion was R=510ohm and C=10nF. I had only parts for a 27k filter. The attenuation at 20khz looked about the same tho.
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Old 2nd March 2013, 04:11 AM   #6496
robbbby is offline robbbby  Canada
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Oh man, i'm going crazy, I don't even know how/where to start toubleshooting so i'm hoping you guys may be able to help me out.
Just tonight while listening to some music, my left channel cut out for a second, and then again. It started doing it quite regularly and at random. Sometimes it would just kick out for a half second, other times up to 4-5 seconds.
I have no idea if it is my dac pre or amp. Is there some way to measure voltage at the input to see if it is dropping before the amp or will putting a meter on the inputs shorts the inputs?
Any advice would be much appreciated.
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Old 2nd March 2013, 07:04 AM   #6497
ds23man is offline ds23man  Netherlands
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Quote:
Originally Posted by robbbby View Post
Oh man, i'm going crazy, I don't even know how/where to start toubleshooting so i'm hoping you guys may be able to help me out.
Just tonight while listening to some music, my left channel cut out for a second, and then again. It started doing it quite regularly and at random. Sometimes it would just kick out for a half second, other times up to 4-5 seconds.
I have no idea if it is my dac pre or amp. Is there some way to measure voltage at the input to see if it is dropping before the amp or will putting a meter on the inputs shorts the inputs?
Any advice would be much appreciated.
Put some caps in series with the inputs of the Ncore to rule out a dc problem from the preceding stage.
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Old 2nd March 2013, 11:09 AM   #6498
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Quote:
Originally Posted by barrows View Post
I have heard people often mention how some class D amplifiers are very sensitive to RF on their inputs. Considering the high input impedance of the module, a really good transformer at its input would have little downside, and if the nC400 is sensitive to HF hash, a transformer could be a good a thing.
I use a AN DAC 4.1X to "drive" my NCores, so I have (really) good Transormers at the input of the NCores. The AN DAC is completely filterless and therefore puts out quite a bit of "high frequency rubbish", but I NEVER had any issues with my NCore's. They just play the music.
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Old 2nd March 2013, 12:05 PM   #6499
ua100k is offline ua100k  United States
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Default NCore Trouble shooting.

Quote:
Originally Posted by robbbby View Post
Oh man, i'm going crazy, I don't even know how/where to start toubleshooting so i'm hoping you guys may be able to help me out.
Just tonight while listening to some music, my left channel cut out for a second, and then again. It started doing it quite regularly and at random. Sometimes it would just kick out for a half second, other times up to 4-5 seconds.
I have no idea if it is my dac pre or amp. Is there some way to measure voltage at the input to see if it is dropping before the amp or will putting a meter on the inputs shorts the inputs?
Any advice would be much appreciated.
From the sounds of it, your power supply is or has gone bad. On the extreme side your speakers are dipping below 1 ohm or have a short.
1. Make sure all the cables are pushed in tight. Especially the control cable.
2. use clips or probes to monitor each of the voltages going to the Nc400 from the power supply. You can poke the probe into the top of the power supply socket to it will stay there and you can watch the voltage. Make sure to check the correct settings are on your meter. Do not measure the current across anything as this will short the voltages. For now you are not concerned about current.
2 - an alternative. Swap the power supply from the other channel to see if it travels. If it does, then it is the power supply. If it does not, then amp or speaker. Swap speaker - just in case. Then swap amp. Once you find it, if it is the NC400 or power supply, Hypex will help you out next.

Good luck Mr. Phelps.
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Old 2nd March 2013, 01:41 PM   #6500
ds23man is offline ds23man  Netherlands
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Quote:
Originally Posted by ua100k View Post
From the sounds of it, your power supply is or has gone bad. On the extreme side your speakers are dipping below 1 ohm or have a short.
1. Make sure all the cables are pushed in tight. Especially the control cable.
2. use clips or probes to monitor each of the voltages going to the Nc400 from the power supply. You can poke the probe into the top of the power supply socket to it will stay there and you can watch the voltage. Make sure to check the correct settings are on your meter. Do not measure the current across anything as this will short the voltages. For now you are not concerned about current.
2 - an alternative. Swap the power supply from the other channel to see if it travels. If it does, then it is the power supply. If it does not, then amp or speaker. Swap speaker - just in case. Then swap amp. Once you find it, if it is the NC400 or power supply, Hypex will help you out next.

Good luck Mr. Phelps.
Swap the inputs first to rule out a dc problem from your preamp!
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