The (HUGE) difference is that you may need to put (perhaps) 47 Ohms in series with the speaker unit to get the effect you want. This resistor will be wasting a very large proportion of the amp power. If you synthesize the high output impedance by using a low value (<1 Ohm) resistor in series with the speaker, and then use a feedback loop to get the desired Z(out), the power wastage is minimal.
So only a small resistor is necessary (1/10 of the load?), and the actual power (and distortion figures) will be almost the same as a normal nc400 with the same load?
Theoretically yes, but of course you will use the '-' input of the amp for the current-derived feedback signal, so the NC will use the '+' input for the input signal, so you lose the balanced i/p arrangement. I have not tried this on a UCD (I don't have any NCs), so I don't know if the amplifier will be happy connected like this, though it should be ok. BUT... a bigger problem is the fact that you are not using a customised gain-block for the amp having a high O/L gain, but a gain-block with around a 26dB gain instead. You may well find that it isn't really practicable to do this and get a high enough value of transconductance for the design.
Now of course in an ideal world you would add an op-amp based input differential gain stage in front of the NC to sum the input signal with the current-derived feedback signal to restore your gain, but this brings up the spectre of instability (gain/phase Bode plot problems) in a big way.
Now of course in an ideal world you would add an op-amp based input differential gain stage in front of the NC to sum the input signal with the current-derived feedback signal to restore your gain, but this brings up the spectre of instability (gain/phase Bode plot problems) in a big way.
have a look at
Op Amp Fundamentals: The Transconductance Amplifier
When you've digested that come back and ask the next level of questions
The output impedance of the closed loop transconductance amplifier is very high because it's part of the closed loop.
Rf isn't the output impedence of the system, it's there as an I/V convertor to provide the voltage signal to the -ve input of the opamp
In stock...Hmmmmmm....(checks account balance)...Well, if my "wire" amp doesn't work (and I'm giving that about a 50% chance), I will be ordering NCores soon.
Found out myself, after a nice cup of coffee: it makes no sense. Open loop gain must be a lot higher than 26 dB.
I see open loop gain being specified 56 dB (typ); the 26 dB is voltage gain of the amp at closed loop.
Has anyone built a 5 channel version of the ncore? I was wondering how you would wire up the power supplies.
Not 5 channels, but I have done 2 x 4 channels. Each pair of nc400's sharing one smps600 each, with a pretty straightforward T-split of the cabling.
Hi, I am building one right now, 5 x nCore with 5 x SMPS. I wire them individualy to a splitter and from there to a Softstart. I consider to use a second Softstart because of the 6 A limitation.
I can see a softstart makes sense with a big toroidal transformer, but does it really do anything useful with a SMPS?
It might. The inrush current is fairy high when the mains side capacitors are charged. I have six SMPS600 powering up at the same time, and the lights in my room really go dim when I power it up.
Intermittent sound and shut down eventually
I have received my two sets of n-core 400 and smps 600 last week, and assembled them this week.
One of them is working pefectly, but the other one worked for just a brief moment. There was sound, but is was intermittent, every 1 sec it was interupted. After some time, there was a click of the smps and since it has been clicking so far (every 2 sec; no lights on nc 400). The SMPS disconnected and powerup just clikcs once, so seems ok.
So it seems it is in some sort of protection mode? DC I suppose?
How do I clear this error state?
I read some threads about not well calibrated dc in and out output and applying 3v to pin 1 and 2 (what does this do exaclty?).
Can anyone share the instructions how to calibrate the DC setting (if that would help to solve the problem)?
I already contacted hypex, but no response yet (it is weekend, so I guess it will be next week).
Can't wait before I have two working n-cores!
Any tips/suggestions what I can do? Thanks in advance!
I have received my two sets of n-core 400 and smps 600 last week, and assembled them this week.
One of them is working pefectly, but the other one worked for just a brief moment. There was sound, but is was intermittent, every 1 sec it was interupted. After some time, there was a click of the smps and since it has been clicking so far (every 2 sec; no lights on nc 400). The SMPS disconnected and powerup just clikcs once, so seems ok.
So it seems it is in some sort of protection mode? DC I suppose?
How do I clear this error state?
I read some threads about not well calibrated dc in and out output and applying 3v to pin 1 and 2 (what does this do exaclty?).
Can anyone share the instructions how to calibrate the DC setting (if that would help to solve the problem)?
I already contacted hypex, but no response yet (it is weekend, so I guess it will be next week).
Can't wait before I have two working n-cores!
Any tips/suggestions what I can do? Thanks in advance!
Two softstarts in series? Both will probably have the same turn-on delay, so the effect will be zip.
Wouldn't a simple delay circuit that turns the SMPSs on in sequence be better? Not sure what happens with a SMPS when you limit the input current with a resistor....
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