Hypex Ncore

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#7,801
nBarrows, nampon gets low in my case by a short connection in the 4 pole connector, sitting in the nCore unit, tied to what has a earth symbol. This should be OK acc to Hypex person I corresponded with.

So pin 3 and 4 in J9 are permanently connected in my amps.This is also what is hooked up to XLR pin 1

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#7,802
OK

understood. I do not understand why you do not just connect a source (anything, preamp, CD player, etc) for test purposes... and make sure the source has no DC as well. Then allow the set up to warm up, and then measure DC at speaker terminals.
If you then have significant DC, contact Hypex for help.
 
#7,803
The problem arises at friends place. I dont have any issues. Just trying to understand.. I can however reproduce the "stand alone situation"... so I will contact Hypex as this to get their view of the "issue"...

Thanks for helping!

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#7,804
Well...

So perhaps your friend's source component has some DC on its output; the nCore is direct coupled, so any DC at the input will be amplfied on the output. Without measuring for DC on your friends source component there is no way to know what is going on.
 
#7,809
Speedskater said:
Currents in the shield (nor anywhere else for that matter) don't drain to ground. They return to their voltage source.
Click to expand...

I believe I understand what you're saying, but don't currents drain (flow) to what they're connected to dependent upon the voltage that's driving them there? No connection, no drain (current flow)

And an induced current (in a shield) will drain (flow) to wherever that conductor is connected?
 
#7,813
ChrisPa said:
An induced current in the secondary of a transformer is trying to get back to the primary?
Click to expand...
The current that left one terminal of the secondary is trying to get back to the other secondary terminal.

An induced current in a wire is trying to get back to something that it has no connection or reference to?
Click to expand...
Maybe we can look at it as the secondary of an air core transformer. So where is the other secondary terminal?

Or then maybe the current is leaking through an unintended capacitor.
 
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#7,814
So reason and resolution for my DC out problem:

"It looks like the 118 mV on the input in amplified 20x causing 2,3 V on the output.

This appears to be caused by a too large common mode offset on the input. We had a small batch of NC400 modules which were adjusted incorrectly due to an error in the testing procedure. This is normally only a problem for unbalanced applications.

You can adjust the common mode voltage as follows:
Measure the voltage between XLR pin 1 and pins 2 or 3 (no other pins shorted). Then adjust potentiometer R95 (VCM) until the meter reads about 0 mV. Do this when the module is at working temperature. At cold temperature the VCM may be set to -300 mV, this will rise to about 0 V when the module warms up.

If the VCM is adjusted correctly and the XLR pins 1 and 3 are shorted, there should be only a few mV DC on the output."

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#7,815
TNT said:
So reason and resolution for my DC out problem:

"It looks like the 118 mV on the input in amplified 20x causing 2,3 V on the output.

This appears to be caused by a too large common mode offset on the input. We had a small batch of NC400 modules which were adjusted incorrectly due to an error in the testing procedure. This is normally only a problem for unbalanced applications.
Click to expand...

Glad to hear it was resolved - and I guess the comforting thing is you can verify (by measuring) that it actually solved the problem.
 
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