Please enlighten me why my question is so special..
Sorry but can the difference measured with a scoop and a multimeter exceed 11 V ?
I confess I do not know much about this !
Well, many class D amps sound really bad, especially the early ones -- ncore does not. So it is reasonable that other SMPSs are also bad, but this one is not. Also, consider that Bruno gives you the option of linear or SMPS with the uCD line, but for the flagship product he considers SMPS to be the best. I am sure that he tried a linear PS and decided that the SMPS was as good or better.
Peaks are probably still there but they do not trigger the ncore auto protection anymore as you lowered the voltage globally (including peaks or ripples if you prefer).
Now the quality of the "DC" input with peaks is another question.
The relation between an avarage and peak voltage measurement for a pure sine is 1.414 (square root of 2). So if your multimeter measures 100VAC the peak could (should) be as high as 141 volts.
if you rectify this and feed capacitors with this signal the outcome won't be a perfect DC but rather DC with an AC component superimposed on it. If you draw a lot of power from your supply this AC component will increase. This is probably the mechanism that caused your NC400 to go into protection mode (the peak was to high, the average was ok)
Just my 2C!
if you rectify this and feed capacitors with this signal the outcome won't be a perfect DC but rather DC with an AC component superimposed on it. If you draw a lot of power from your supply this AC component will increase. This is probably the mechanism that caused your NC400 to go into protection mode (the peak was to high, the average was ok)
Just my 2C!
And in addition to that, a class D amp probably causes a fair bit of reverse currents that add temporary peaks unless the power supply can absorb them.
Right, so now your power supply probably stays under the specified 75 V trigger point, even when the AC ripple and back current transients are added to your 59.9 V.
I suggest you measure the peak voltage of your power supply using your oscilloscope (just set it to something like 1V/div scale, and count how many squares there are from the top of the highest peaks down to the 0 line (check the 0 line by shorting the scope input).
Yes. If your multimeter shows a 60V average value, the peak value can be up to 84 V (worst case, assuming your reservoir capacitors would be totally insufficient), plus any back-current induced extra voltage.
I'm with you there Julf....... see quote from SMPS 600 info which is the same as all the Hypex SMPS info......
" Conventional Switch Mode Power Supplies are commonly unsuitable for audio purposes due to poor
peak power capabilities and the inability to handle reversed currents generated by Class D amplifiers
as a load. The Hypex SMPS600 achieves these things by using an advanced over current protection
circuit, a highly efficient 2 quadrant DC/DC converter which is capable of handling reversed currents
and has a peak power handling of many times its rated power. "
Hmmmmmm
OK, so at the max current the nc400 is capable of driving, the ripple would be 8.3 V. But I have no idea how large the initial surge current is.
But the back-current voltage peaks - what's the inductance of your capacitors?
A D-class amplifier (any D-class amplifier, not just the ncore) is a very different beast than an analog amplifier.
Just talked with a very educated guy who tells me you guys are way beyond resonabelity . Øh I do not now this was ok English !
We are what we are. Not much beyond that.
But the capacitors are there to take those peaks. 6x 10.000 uf in each mono amp.
Just talked with a very educated guy who tells me you guys are way beyond resonabelity . Øh I do not now this was ok English !
Still I would recommend, like some others here on the forum, to use your scoop to measure your voltage.
During my electrical engineering education we were always told "Meten is weten"....
Hi Roberto,
I had the same problem-500mv DC offset on speakers. What worked for me is to adjust R136 first to zero offset at speaker posts (inputs open and speakers disconnected) and then zero dc offset between hot(red/pin2) and ground(pin1) using R95. If you check dc offset at speakers it might need some final adjustment. The pots are very sensitive around zero though.
Hope this helps.
I had the same problem-500mv DC offset on speakers. What worked for me is to adjust R136 first to zero offset at speaker posts (inputs open and speakers disconnected) and then zero dc offset between hot(red/pin2) and ground(pin1) using R95. If you check dc offset at speakers it might need some final adjustment. The pots are very sensitive around zero though.
Hope this helps.
Should be possible when the impedance of the power supply is low enough. Use a big tranny and low esr caps or maybe an array of smaller caps + beefy rectifier bridges. With such an setup an inrush current limiting circuit is a good idea...
Agree. That is why I was asking about the inductance of the caps. You definitely need low esr - and low esr at higher frequencies.
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